~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/kernel/fork.c

Version: ~ [ linux-5.15-rc6 ] ~ [ linux-5.14.14 ] ~ [ linux-5.13.19 ] ~ [ linux-5.12.19 ] ~ [ linux-5.11.22 ] ~ [ linux-5.10.75 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.155 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.213 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.252 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.287 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.289 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.18.140 ] ~ [ linux-3.16.85 ] ~ [ linux-3.14.79 ] ~ [ linux-3.12.74 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  *  linux/kernel/fork.c
  4  *
  5  *  Copyright (C) 1991, 1992  Linus Torvalds
  6  */
  7 
  8 /*
  9  *  'fork.c' contains the help-routines for the 'fork' system call
 10  * (see also entry.S and others).
 11  * Fork is rather simple, once you get the hang of it, but the memory
 12  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
 13  */
 14 
 15 #include <linux/anon_inodes.h>
 16 #include <linux/slab.h>
 17 #include <linux/sched/autogroup.h>
 18 #include <linux/sched/mm.h>
 19 #include <linux/sched/coredump.h>
 20 #include <linux/sched/user.h>
 21 #include <linux/sched/numa_balancing.h>
 22 #include <linux/sched/stat.h>
 23 #include <linux/sched/task.h>
 24 #include <linux/sched/task_stack.h>
 25 #include <linux/sched/cputime.h>
 26 #include <linux/seq_file.h>
 27 #include <linux/rtmutex.h>
 28 #include <linux/init.h>
 29 #include <linux/unistd.h>
 30 #include <linux/module.h>
 31 #include <linux/vmalloc.h>
 32 #include <linux/completion.h>
 33 #include <linux/personality.h>
 34 #include <linux/mempolicy.h>
 35 #include <linux/sem.h>
 36 #include <linux/file.h>
 37 #include <linux/fdtable.h>
 38 #include <linux/iocontext.h>
 39 #include <linux/key.h>
 40 #include <linux/binfmts.h>
 41 #include <linux/mman.h>
 42 #include <linux/mmu_notifier.h>
 43 #include <linux/fs.h>
 44 #include <linux/mm.h>
 45 #include <linux/vmacache.h>
 46 #include <linux/nsproxy.h>
 47 #include <linux/capability.h>
 48 #include <linux/cpu.h>
 49 #include <linux/cgroup.h>
 50 #include <linux/security.h>
 51 #include <linux/hugetlb.h>
 52 #include <linux/seccomp.h>
 53 #include <linux/swap.h>
 54 #include <linux/syscalls.h>
 55 #include <linux/jiffies.h>
 56 #include <linux/futex.h>
 57 #include <linux/compat.h>
 58 #include <linux/kthread.h>
 59 #include <linux/task_io_accounting_ops.h>
 60 #include <linux/rcupdate.h>
 61 #include <linux/ptrace.h>
 62 #include <linux/mount.h>
 63 #include <linux/audit.h>
 64 #include <linux/memcontrol.h>
 65 #include <linux/ftrace.h>
 66 #include <linux/proc_fs.h>
 67 #include <linux/profile.h>
 68 #include <linux/rmap.h>
 69 #include <linux/ksm.h>
 70 #include <linux/acct.h>
 71 #include <linux/userfaultfd_k.h>
 72 #include <linux/tsacct_kern.h>
 73 #include <linux/cn_proc.h>
 74 #include <linux/freezer.h>
 75 #include <linux/delayacct.h>
 76 #include <linux/taskstats_kern.h>
 77 #include <linux/random.h>
 78 #include <linux/tty.h>
 79 #include <linux/blkdev.h>
 80 #include <linux/fs_struct.h>
 81 #include <linux/magic.h>
 82 #include <linux/perf_event.h>
 83 #include <linux/posix-timers.h>
 84 #include <linux/user-return-notifier.h>
 85 #include <linux/oom.h>
 86 #include <linux/khugepaged.h>
 87 #include <linux/signalfd.h>
 88 #include <linux/uprobes.h>
 89 #include <linux/aio.h>
 90 #include <linux/compiler.h>
 91 #include <linux/sysctl.h>
 92 #include <linux/kcov.h>
 93 #include <linux/livepatch.h>
 94 #include <linux/thread_info.h>
 95 #include <linux/stackleak.h>
 96 #include <linux/kasan.h>
 97 #include <linux/scs.h>
 98 #include <linux/io_uring.h>
 99 
100 #include <asm/pgalloc.h>
101 #include <linux/uaccess.h>
102 #include <asm/mmu_context.h>
103 #include <asm/cacheflush.h>
104 #include <asm/tlbflush.h>
105 
106 #include <trace/events/sched.h>
107 
108 #define CREATE_TRACE_POINTS
109 #include <trace/events/task.h>
110 
111 /*
112  * Minimum number of threads to boot the kernel
113  */
114 #define MIN_THREADS 20
115 
116 /*
117  * Maximum number of threads
118  */
119 #define MAX_THREADS FUTEX_TID_MASK
120 
121 /*
122  * Protected counters by write_lock_irq(&tasklist_lock)
123  */
124 unsigned long total_forks;      /* Handle normal Linux uptimes. */
125 int nr_threads;                 /* The idle threads do not count.. */
126 
127 static int max_threads;         /* tunable limit on nr_threads */
128 
129 #define NAMED_ARRAY_INDEX(x)    [x] = __stringify(x)
130 
131 static const char * const resident_page_types[] = {
132         NAMED_ARRAY_INDEX(MM_FILEPAGES),
133         NAMED_ARRAY_INDEX(MM_ANONPAGES),
134         NAMED_ARRAY_INDEX(MM_SWAPENTS),
135         NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
136 };
137 
138 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
139 
140 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
141 
142 #ifdef CONFIG_PROVE_RCU
143 int lockdep_tasklist_lock_is_held(void)
144 {
145         return lockdep_is_held(&tasklist_lock);
146 }
147 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
148 #endif /* #ifdef CONFIG_PROVE_RCU */
149 
150 int nr_processes(void)
151 {
152         int cpu;
153         int total = 0;
154 
155         for_each_possible_cpu(cpu)
156                 total += per_cpu(process_counts, cpu);
157 
158         return total;
159 }
160 
161 void __weak arch_release_task_struct(struct task_struct *tsk)
162 {
163 }
164 
165 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
166 static struct kmem_cache *task_struct_cachep;
167 
168 static inline struct task_struct *alloc_task_struct_node(int node)
169 {
170         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
171 }
172 
173 static inline void free_task_struct(struct task_struct *tsk)
174 {
175         kmem_cache_free(task_struct_cachep, tsk);
176 }
177 #endif
178 
179 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
180 
181 /*
182  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
183  * kmemcache based allocator.
184  */
185 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
186 
187 #ifdef CONFIG_VMAP_STACK
188 /*
189  * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
190  * flush.  Try to minimize the number of calls by caching stacks.
191  */
192 #define NR_CACHED_STACKS 2
193 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
194 
195 static int free_vm_stack_cache(unsigned int cpu)
196 {
197         struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
198         int i;
199 
200         for (i = 0; i < NR_CACHED_STACKS; i++) {
201                 struct vm_struct *vm_stack = cached_vm_stacks[i];
202 
203                 if (!vm_stack)
204                         continue;
205 
206                 vfree(vm_stack->addr);
207                 cached_vm_stacks[i] = NULL;
208         }
209 
210         return 0;
211 }
212 #endif
213 
214 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
215 {
216 #ifdef CONFIG_VMAP_STACK
217         void *stack;
218         int i;
219 
220         for (i = 0; i < NR_CACHED_STACKS; i++) {
221                 struct vm_struct *s;
222 
223                 s = this_cpu_xchg(cached_stacks[i], NULL);
224 
225                 if (!s)
226                         continue;
227 
228                 /* Mark stack accessible for KASAN. */
229                 kasan_unpoison_range(s->addr, THREAD_SIZE);
230 
231                 /* Clear stale pointers from reused stack. */
232                 memset(s->addr, 0, THREAD_SIZE);
233 
234                 tsk->stack_vm_area = s;
235                 tsk->stack = s->addr;
236                 return s->addr;
237         }
238 
239         /*
240          * Allocated stacks are cached and later reused by new threads,
241          * so memcg accounting is performed manually on assigning/releasing
242          * stacks to tasks. Drop __GFP_ACCOUNT.
243          */
244         stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
245                                      VMALLOC_START, VMALLOC_END,
246                                      THREADINFO_GFP & ~__GFP_ACCOUNT,
247                                      PAGE_KERNEL,
248                                      0, node, __builtin_return_address(0));
249 
250         /*
251          * We can't call find_vm_area() in interrupt context, and
252          * free_thread_stack() can be called in interrupt context,
253          * so cache the vm_struct.
254          */
255         if (stack) {
256                 tsk->stack_vm_area = find_vm_area(stack);
257                 tsk->stack = stack;
258         }
259         return stack;
260 #else
261         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
262                                              THREAD_SIZE_ORDER);
263 
264         if (likely(page)) {
265                 tsk->stack = kasan_reset_tag(page_address(page));
266                 return tsk->stack;
267         }
268         return NULL;
269 #endif
270 }
271 
272 static inline void free_thread_stack(struct task_struct *tsk)
273 {
274 #ifdef CONFIG_VMAP_STACK
275         struct vm_struct *vm = task_stack_vm_area(tsk);
276 
277         if (vm) {
278                 int i;
279 
280                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
281                         memcg_kmem_uncharge_page(vm->pages[i], 0);
282 
283                 for (i = 0; i < NR_CACHED_STACKS; i++) {
284                         if (this_cpu_cmpxchg(cached_stacks[i],
285                                         NULL, tsk->stack_vm_area) != NULL)
286                                 continue;
287 
288                         return;
289                 }
290 
291                 vfree_atomic(tsk->stack);
292                 return;
293         }
294 #endif
295 
296         __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
297 }
298 # else
299 static struct kmem_cache *thread_stack_cache;
300 
301 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
302                                                   int node)
303 {
304         unsigned long *stack;
305         stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
306         stack = kasan_reset_tag(stack);
307         tsk->stack = stack;
308         return stack;
309 }
310 
311 static void free_thread_stack(struct task_struct *tsk)
312 {
313         kmem_cache_free(thread_stack_cache, tsk->stack);
314 }
315 
316 void thread_stack_cache_init(void)
317 {
318         thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
319                                         THREAD_SIZE, THREAD_SIZE, 0, 0,
320                                         THREAD_SIZE, NULL);
321         BUG_ON(thread_stack_cache == NULL);
322 }
323 # endif
324 #endif
325 
326 /* SLAB cache for signal_struct structures (tsk->signal) */
327 static struct kmem_cache *signal_cachep;
328 
329 /* SLAB cache for sighand_struct structures (tsk->sighand) */
330 struct kmem_cache *sighand_cachep;
331 
332 /* SLAB cache for files_struct structures (tsk->files) */
333 struct kmem_cache *files_cachep;
334 
335 /* SLAB cache for fs_struct structures (tsk->fs) */
336 struct kmem_cache *fs_cachep;
337 
338 /* SLAB cache for vm_area_struct structures */
339 static struct kmem_cache *vm_area_cachep;
340 
341 /* SLAB cache for mm_struct structures (tsk->mm) */
342 static struct kmem_cache *mm_cachep;
343 
344 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
345 {
346         struct vm_area_struct *vma;
347 
348         vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
349         if (vma)
350                 vma_init(vma, mm);
351         return vma;
352 }
353 
354 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
355 {
356         struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
357 
358         if (new) {
359                 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
360                 ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
361                 /*
362                  * orig->shared.rb may be modified concurrently, but the clone
363                  * will be reinitialized.
364                  */
365                 *new = data_race(*orig);
366                 INIT_LIST_HEAD(&new->anon_vma_chain);
367                 new->vm_next = new->vm_prev = NULL;
368         }
369         return new;
370 }
371 
372 void vm_area_free(struct vm_area_struct *vma)
373 {
374         kmem_cache_free(vm_area_cachep, vma);
375 }
376 
377 static void account_kernel_stack(struct task_struct *tsk, int account)
378 {
379         void *stack = task_stack_page(tsk);
380         struct vm_struct *vm = task_stack_vm_area(tsk);
381 
382 
383         /* All stack pages are in the same node. */
384         if (vm)
385                 mod_lruvec_page_state(vm->pages[0], NR_KERNEL_STACK_KB,
386                                       account * (THREAD_SIZE / 1024));
387         else
388                 mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
389                                       account * (THREAD_SIZE / 1024));
390 }
391 
392 static int memcg_charge_kernel_stack(struct task_struct *tsk)
393 {
394 #ifdef CONFIG_VMAP_STACK
395         struct vm_struct *vm = task_stack_vm_area(tsk);
396         int ret;
397 
398         BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
399 
400         if (vm) {
401                 int i;
402 
403                 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
404 
405                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
406                         /*
407                          * If memcg_kmem_charge_page() fails, page's
408                          * memory cgroup pointer is NULL, and
409                          * memcg_kmem_uncharge_page() in free_thread_stack()
410                          * will ignore this page.
411                          */
412                         ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL,
413                                                      0);
414                         if (ret)
415                                 return ret;
416                 }
417         }
418 #endif
419         return 0;
420 }
421 
422 static void release_task_stack(struct task_struct *tsk)
423 {
424         if (WARN_ON(tsk->state != TASK_DEAD))
425                 return;  /* Better to leak the stack than to free prematurely */
426 
427         account_kernel_stack(tsk, -1);
428         free_thread_stack(tsk);
429         tsk->stack = NULL;
430 #ifdef CONFIG_VMAP_STACK
431         tsk->stack_vm_area = NULL;
432 #endif
433 }
434 
435 #ifdef CONFIG_THREAD_INFO_IN_TASK
436 void put_task_stack(struct task_struct *tsk)
437 {
438         if (refcount_dec_and_test(&tsk->stack_refcount))
439                 release_task_stack(tsk);
440 }
441 #endif
442 
443 void free_task(struct task_struct *tsk)
444 {
445         scs_release(tsk);
446 
447 #ifndef CONFIG_THREAD_INFO_IN_TASK
448         /*
449          * The task is finally done with both the stack and thread_info,
450          * so free both.
451          */
452         release_task_stack(tsk);
453 #else
454         /*
455          * If the task had a separate stack allocation, it should be gone
456          * by now.
457          */
458         WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
459 #endif
460         rt_mutex_debug_task_free(tsk);
461         ftrace_graph_exit_task(tsk);
462         arch_release_task_struct(tsk);
463         if (tsk->flags & PF_KTHREAD)
464                 free_kthread_struct(tsk);
465         free_task_struct(tsk);
466 }
467 EXPORT_SYMBOL(free_task);
468 
469 #ifdef CONFIG_MMU
470 static __latent_entropy int dup_mmap(struct mm_struct *mm,
471                                         struct mm_struct *oldmm)
472 {
473         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
474         struct rb_node **rb_link, *rb_parent;
475         int retval;
476         unsigned long charge;
477         LIST_HEAD(uf);
478 
479         uprobe_start_dup_mmap();
480         if (mmap_write_lock_killable(oldmm)) {
481                 retval = -EINTR;
482                 goto fail_uprobe_end;
483         }
484         flush_cache_dup_mm(oldmm);
485         uprobe_dup_mmap(oldmm, mm);
486         /*
487          * Not linked in yet - no deadlock potential:
488          */
489         mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
490 
491         /* No ordering required: file already has been exposed. */
492         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
493 
494         mm->total_vm = oldmm->total_vm;
495         mm->data_vm = oldmm->data_vm;
496         mm->exec_vm = oldmm->exec_vm;
497         mm->stack_vm = oldmm->stack_vm;
498 
499         rb_link = &mm->mm_rb.rb_node;
500         rb_parent = NULL;
501         pprev = &mm->mmap;
502         retval = ksm_fork(mm, oldmm);
503         if (retval)
504                 goto out;
505         retval = khugepaged_fork(mm, oldmm);
506         if (retval)
507                 goto out;
508 
509         prev = NULL;
510         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
511                 struct file *file;
512 
513                 if (mpnt->vm_flags & VM_DONTCOPY) {
514                         vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
515                         continue;
516                 }
517                 charge = 0;
518                 /*
519                  * Don't duplicate many vmas if we've been oom-killed (for
520                  * example)
521                  */
522                 if (fatal_signal_pending(current)) {
523                         retval = -EINTR;
524                         goto out;
525                 }
526                 if (mpnt->vm_flags & VM_ACCOUNT) {
527                         unsigned long len = vma_pages(mpnt);
528 
529                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
530                                 goto fail_nomem;
531                         charge = len;
532                 }
533                 tmp = vm_area_dup(mpnt);
534                 if (!tmp)
535                         goto fail_nomem;
536                 retval = vma_dup_policy(mpnt, tmp);
537                 if (retval)
538                         goto fail_nomem_policy;
539                 tmp->vm_mm = mm;
540                 retval = dup_userfaultfd(tmp, &uf);
541                 if (retval)
542                         goto fail_nomem_anon_vma_fork;
543                 if (tmp->vm_flags & VM_WIPEONFORK) {
544                         /*
545                          * VM_WIPEONFORK gets a clean slate in the child.
546                          * Don't prepare anon_vma until fault since we don't
547                          * copy page for current vma.
548                          */
549                         tmp->anon_vma = NULL;
550                 } else if (anon_vma_fork(tmp, mpnt))
551                         goto fail_nomem_anon_vma_fork;
552                 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
553                 file = tmp->vm_file;
554                 if (file) {
555                         struct inode *inode = file_inode(file);
556                         struct address_space *mapping = file->f_mapping;
557 
558                         get_file(file);
559                         if (tmp->vm_flags & VM_DENYWRITE)
560                                 put_write_access(inode);
561                         i_mmap_lock_write(mapping);
562                         if (tmp->vm_flags & VM_SHARED)
563                                 mapping_allow_writable(mapping);
564                         flush_dcache_mmap_lock(mapping);
565                         /* insert tmp into the share list, just after mpnt */
566                         vma_interval_tree_insert_after(tmp, mpnt,
567                                         &mapping->i_mmap);
568                         flush_dcache_mmap_unlock(mapping);
569                         i_mmap_unlock_write(mapping);
570                 }
571 
572                 /*
573                  * Clear hugetlb-related page reserves for children. This only
574                  * affects MAP_PRIVATE mappings. Faults generated by the child
575                  * are not guaranteed to succeed, even if read-only
576                  */
577                 if (is_vm_hugetlb_page(tmp))
578                         reset_vma_resv_huge_pages(tmp);
579 
580                 /*
581                  * Link in the new vma and copy the page table entries.
582                  */
583                 *pprev = tmp;
584                 pprev = &tmp->vm_next;
585                 tmp->vm_prev = prev;
586                 prev = tmp;
587 
588                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
589                 rb_link = &tmp->vm_rb.rb_right;
590                 rb_parent = &tmp->vm_rb;
591 
592                 mm->map_count++;
593                 if (!(tmp->vm_flags & VM_WIPEONFORK))
594                         retval = copy_page_range(tmp, mpnt);
595 
596                 if (tmp->vm_ops && tmp->vm_ops->open)
597                         tmp->vm_ops->open(tmp);
598 
599                 if (retval)
600                         goto out;
601         }
602         /* a new mm has just been created */
603         retval = arch_dup_mmap(oldmm, mm);
604 out:
605         mmap_write_unlock(mm);
606         flush_tlb_mm(oldmm);
607         mmap_write_unlock(oldmm);
608         dup_userfaultfd_complete(&uf);
609 fail_uprobe_end:
610         uprobe_end_dup_mmap();
611         return retval;
612 fail_nomem_anon_vma_fork:
613         mpol_put(vma_policy(tmp));
614 fail_nomem_policy:
615         vm_area_free(tmp);
616 fail_nomem:
617         retval = -ENOMEM;
618         vm_unacct_memory(charge);
619         goto out;
620 }
621 
622 static inline int mm_alloc_pgd(struct mm_struct *mm)
623 {
624         mm->pgd = pgd_alloc(mm);
625         if (unlikely(!mm->pgd))
626                 return -ENOMEM;
627         return 0;
628 }
629 
630 static inline void mm_free_pgd(struct mm_struct *mm)
631 {
632         pgd_free(mm, mm->pgd);
633 }
634 #else
635 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
636 {
637         mmap_write_lock(oldmm);
638         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
639         mmap_write_unlock(oldmm);
640         return 0;
641 }
642 #define mm_alloc_pgd(mm)        (0)
643 #define mm_free_pgd(mm)
644 #endif /* CONFIG_MMU */
645 
646 static void check_mm(struct mm_struct *mm)
647 {
648         int i;
649 
650         BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
651                          "Please make sure 'struct resident_page_types[]' is updated as well");
652 
653         for (i = 0; i < NR_MM_COUNTERS; i++) {
654                 long x = atomic_long_read(&mm->rss_stat.count[i]);
655 
656                 if (unlikely(x))
657                         pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
658                                  mm, resident_page_types[i], x);
659         }
660 
661         if (mm_pgtables_bytes(mm))
662                 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
663                                 mm_pgtables_bytes(mm));
664 
665 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
666         VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
667 #endif
668 }
669 
670 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
671 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
672 
673 /*
674  * Called when the last reference to the mm
675  * is dropped: either by a lazy thread or by
676  * mmput. Free the page directory and the mm.
677  */
678 void __mmdrop(struct mm_struct *mm)
679 {
680         BUG_ON(mm == &init_mm);
681         WARN_ON_ONCE(mm == current->mm);
682         WARN_ON_ONCE(mm == current->active_mm);
683         mm_free_pgd(mm);
684         destroy_context(mm);
685         mmu_notifier_subscriptions_destroy(mm);
686         check_mm(mm);
687         put_user_ns(mm->user_ns);
688         free_mm(mm);
689 }
690 EXPORT_SYMBOL_GPL(__mmdrop);
691 
692 static void mmdrop_async_fn(struct work_struct *work)
693 {
694         struct mm_struct *mm;
695 
696         mm = container_of(work, struct mm_struct, async_put_work);
697         __mmdrop(mm);
698 }
699 
700 static void mmdrop_async(struct mm_struct *mm)
701 {
702         if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
703                 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
704                 schedule_work(&mm->async_put_work);
705         }
706 }
707 
708 static inline void free_signal_struct(struct signal_struct *sig)
709 {
710         taskstats_tgid_free(sig);
711         sched_autogroup_exit(sig);
712         /*
713          * __mmdrop is not safe to call from softirq context on x86 due to
714          * pgd_dtor so postpone it to the async context
715          */
716         if (sig->oom_mm)
717                 mmdrop_async(sig->oom_mm);
718         kmem_cache_free(signal_cachep, sig);
719 }
720 
721 static inline void put_signal_struct(struct signal_struct *sig)
722 {
723         if (refcount_dec_and_test(&sig->sigcnt))
724                 free_signal_struct(sig);
725 }
726 
727 void __put_task_struct(struct task_struct *tsk)
728 {
729         WARN_ON(!tsk->exit_state);
730         WARN_ON(refcount_read(&tsk->usage));
731         WARN_ON(tsk == current);
732 
733         io_uring_free(tsk);
734         cgroup_free(tsk);
735         task_numa_free(tsk, true);
736         security_task_free(tsk);
737         exit_creds(tsk);
738         delayacct_tsk_free(tsk);
739         put_signal_struct(tsk->signal);
740 
741         if (!profile_handoff_task(tsk))
742                 free_task(tsk);
743 }
744 EXPORT_SYMBOL_GPL(__put_task_struct);
745 
746 void __init __weak arch_task_cache_init(void) { }
747 
748 /*
749  * set_max_threads
750  */
751 static void set_max_threads(unsigned int max_threads_suggested)
752 {
753         u64 threads;
754         unsigned long nr_pages = totalram_pages();
755 
756         /*
757          * The number of threads shall be limited such that the thread
758          * structures may only consume a small part of the available memory.
759          */
760         if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
761                 threads = MAX_THREADS;
762         else
763                 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
764                                     (u64) THREAD_SIZE * 8UL);
765 
766         if (threads > max_threads_suggested)
767                 threads = max_threads_suggested;
768 
769         max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
770 }
771 
772 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
773 /* Initialized by the architecture: */
774 int arch_task_struct_size __read_mostly;
775 #endif
776 
777 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
778 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
779 {
780         /* Fetch thread_struct whitelist for the architecture. */
781         arch_thread_struct_whitelist(offset, size);
782 
783         /*
784          * Handle zero-sized whitelist or empty thread_struct, otherwise
785          * adjust offset to position of thread_struct in task_struct.
786          */
787         if (unlikely(*size == 0))
788                 *offset = 0;
789         else
790                 *offset += offsetof(struct task_struct, thread);
791 }
792 #endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
793 
794 void __init fork_init(void)
795 {
796         int i;
797 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
798 #ifndef ARCH_MIN_TASKALIGN
799 #define ARCH_MIN_TASKALIGN      0
800 #endif
801         int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
802         unsigned long useroffset, usersize;
803 
804         /* create a slab on which task_structs can be allocated */
805         task_struct_whitelist(&useroffset, &usersize);
806         task_struct_cachep = kmem_cache_create_usercopy("task_struct",
807                         arch_task_struct_size, align,
808                         SLAB_PANIC|SLAB_ACCOUNT,
809                         useroffset, usersize, NULL);
810 #endif
811 
812         /* do the arch specific task caches init */
813         arch_task_cache_init();
814 
815         set_max_threads(MAX_THREADS);
816 
817         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
818         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
819         init_task.signal->rlim[RLIMIT_SIGPENDING] =
820                 init_task.signal->rlim[RLIMIT_NPROC];
821 
822         for (i = 0; i < UCOUNT_COUNTS; i++)
823                 init_user_ns.ucount_max[i] = max_threads/2;
824 
825 #ifdef CONFIG_VMAP_STACK
826         cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
827                           NULL, free_vm_stack_cache);
828 #endif
829 
830         scs_init();
831 
832         lockdep_init_task(&init_task);
833         uprobes_init();
834 }
835 
836 int __weak arch_dup_task_struct(struct task_struct *dst,
837                                                struct task_struct *src)
838 {
839         *dst = *src;
840         return 0;
841 }
842 
843 void set_task_stack_end_magic(struct task_struct *tsk)
844 {
845         unsigned long *stackend;
846 
847         stackend = end_of_stack(tsk);
848         *stackend = STACK_END_MAGIC;    /* for overflow detection */
849 }
850 
851 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
852 {
853         struct task_struct *tsk;
854         unsigned long *stack;
855         struct vm_struct *stack_vm_area __maybe_unused;
856         int err;
857 
858         if (node == NUMA_NO_NODE)
859                 node = tsk_fork_get_node(orig);
860         tsk = alloc_task_struct_node(node);
861         if (!tsk)
862                 return NULL;
863 
864         stack = alloc_thread_stack_node(tsk, node);
865         if (!stack)
866                 goto free_tsk;
867 
868         if (memcg_charge_kernel_stack(tsk))
869                 goto free_stack;
870 
871         stack_vm_area = task_stack_vm_area(tsk);
872 
873         err = arch_dup_task_struct(tsk, orig);
874 
875         /*
876          * arch_dup_task_struct() clobbers the stack-related fields.  Make
877          * sure they're properly initialized before using any stack-related
878          * functions again.
879          */
880         tsk->stack = stack;
881 #ifdef CONFIG_VMAP_STACK
882         tsk->stack_vm_area = stack_vm_area;
883 #endif
884 #ifdef CONFIG_THREAD_INFO_IN_TASK
885         refcount_set(&tsk->stack_refcount, 1);
886 #endif
887 
888         if (err)
889                 goto free_stack;
890 
891         err = scs_prepare(tsk, node);
892         if (err)
893                 goto free_stack;
894 
895 #ifdef CONFIG_SECCOMP
896         /*
897          * We must handle setting up seccomp filters once we're under
898          * the sighand lock in case orig has changed between now and
899          * then. Until then, filter must be NULL to avoid messing up
900          * the usage counts on the error path calling free_task.
901          */
902         tsk->seccomp.filter = NULL;
903 #endif
904 
905         setup_thread_stack(tsk, orig);
906         clear_user_return_notifier(tsk);
907         clear_tsk_need_resched(tsk);
908         set_task_stack_end_magic(tsk);
909         clear_syscall_work_syscall_user_dispatch(tsk);
910 
911 #ifdef CONFIG_STACKPROTECTOR
912         tsk->stack_canary = get_random_canary();
913 #endif
914         if (orig->cpus_ptr == &orig->cpus_mask)
915                 tsk->cpus_ptr = &tsk->cpus_mask;
916 
917         /*
918          * One for the user space visible state that goes away when reaped.
919          * One for the scheduler.
920          */
921         refcount_set(&tsk->rcu_users, 2);
922         /* One for the rcu users */
923         refcount_set(&tsk->usage, 1);
924 #ifdef CONFIG_BLK_DEV_IO_TRACE
925         tsk->btrace_seq = 0;
926 #endif
927         tsk->splice_pipe = NULL;
928         tsk->task_frag.page = NULL;
929         tsk->wake_q.next = NULL;
930 
931         account_kernel_stack(tsk, 1);
932 
933         kcov_task_init(tsk);
934         kmap_local_fork(tsk);
935 
936 #ifdef CONFIG_FAULT_INJECTION
937         tsk->fail_nth = 0;
938 #endif
939 
940 #ifdef CONFIG_BLK_CGROUP
941         tsk->throttle_queue = NULL;
942         tsk->use_memdelay = 0;
943 #endif
944 
945 #ifdef CONFIG_MEMCG
946         tsk->active_memcg = NULL;
947 #endif
948         return tsk;
949 
950 free_stack:
951         free_thread_stack(tsk);
952 free_tsk:
953         free_task_struct(tsk);
954         return NULL;
955 }
956 
957 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
958 
959 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
960 
961 static int __init coredump_filter_setup(char *s)
962 {
963         default_dump_filter =
964                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
965                 MMF_DUMP_FILTER_MASK;
966         return 1;
967 }
968 
969 __setup("coredump_filter=", coredump_filter_setup);
970 
971 #include <linux/init_task.h>
972 
973 static void mm_init_aio(struct mm_struct *mm)
974 {
975 #ifdef CONFIG_AIO
976         spin_lock_init(&mm->ioctx_lock);
977         mm->ioctx_table = NULL;
978 #endif
979 }
980 
981 static __always_inline void mm_clear_owner(struct mm_struct *mm,
982                                            struct task_struct *p)
983 {
984 #ifdef CONFIG_MEMCG
985         if (mm->owner == p)
986                 WRITE_ONCE(mm->owner, NULL);
987 #endif
988 }
989 
990 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
991 {
992 #ifdef CONFIG_MEMCG
993         mm->owner = p;
994 #endif
995 }
996 
997 static void mm_init_pasid(struct mm_struct *mm)
998 {
999 #ifdef CONFIG_IOMMU_SUPPORT
1000         mm->pasid = INIT_PASID;
1001 #endif
1002 }
1003 
1004 static void mm_init_uprobes_state(struct mm_struct *mm)
1005 {
1006 #ifdef CONFIG_UPROBES
1007         mm->uprobes_state.xol_area = NULL;
1008 #endif
1009 }
1010 
1011 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1012         struct user_namespace *user_ns)
1013 {
1014         mm->mmap = NULL;
1015         mm->mm_rb = RB_ROOT;
1016         mm->vmacache_seqnum = 0;
1017         atomic_set(&mm->mm_users, 1);
1018         atomic_set(&mm->mm_count, 1);
1019         seqcount_init(&mm->write_protect_seq);
1020         mmap_init_lock(mm);
1021         INIT_LIST_HEAD(&mm->mmlist);
1022         mm->core_state = NULL;
1023         mm_pgtables_bytes_init(mm);
1024         mm->map_count = 0;
1025         mm->locked_vm = 0;
1026         atomic_set(&mm->has_pinned, 0);
1027         atomic64_set(&mm->pinned_vm, 0);
1028         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1029         spin_lock_init(&mm->page_table_lock);
1030         spin_lock_init(&mm->arg_lock);
1031         mm_init_cpumask(mm);
1032         mm_init_aio(mm);
1033         mm_init_owner(mm, p);
1034         mm_init_pasid(mm);
1035         RCU_INIT_POINTER(mm->exe_file, NULL);
1036         mmu_notifier_subscriptions_init(mm);
1037         init_tlb_flush_pending(mm);
1038 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1039         mm->pmd_huge_pte = NULL;
1040 #endif
1041         mm_init_uprobes_state(mm);
1042 
1043         if (current->mm) {
1044                 mm->flags = current->mm->flags & MMF_INIT_MASK;
1045                 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1046         } else {
1047                 mm->flags = default_dump_filter;
1048                 mm->def_flags = 0;
1049         }
1050 
1051         if (mm_alloc_pgd(mm))
1052                 goto fail_nopgd;
1053 
1054         if (init_new_context(p, mm))
1055                 goto fail_nocontext;
1056 
1057         mm->user_ns = get_user_ns(user_ns);
1058         return mm;
1059 
1060 fail_nocontext:
1061         mm_free_pgd(mm);
1062 fail_nopgd:
1063         free_mm(mm);
1064         return NULL;
1065 }
1066 
1067 /*
1068  * Allocate and initialize an mm_struct.
1069  */
1070 struct mm_struct *mm_alloc(void)
1071 {
1072         struct mm_struct *mm;
1073 
1074         mm = allocate_mm();
1075         if (!mm)
1076                 return NULL;
1077 
1078         memset(mm, 0, sizeof(*mm));
1079         return mm_init(mm, current, current_user_ns());
1080 }
1081 
1082 static inline void __mmput(struct mm_struct *mm)
1083 {
1084         VM_BUG_ON(atomic_read(&mm->mm_users));
1085 
1086         uprobe_clear_state(mm);
1087         exit_aio(mm);
1088         ksm_exit(mm);
1089         khugepaged_exit(mm); /* must run before exit_mmap */
1090         exit_mmap(mm);
1091         mm_put_huge_zero_page(mm);
1092         set_mm_exe_file(mm, NULL);
1093         if (!list_empty(&mm->mmlist)) {
1094                 spin_lock(&mmlist_lock);
1095                 list_del(&mm->mmlist);
1096                 spin_unlock(&mmlist_lock);
1097         }
1098         if (mm->binfmt)
1099                 module_put(mm->binfmt->module);
1100         mmdrop(mm);
1101 }
1102 
1103 /*
1104  * Decrement the use count and release all resources for an mm.
1105  */
1106 void mmput(struct mm_struct *mm)
1107 {
1108         might_sleep();
1109 
1110         if (atomic_dec_and_test(&mm->mm_users))
1111                 __mmput(mm);
1112 }
1113 EXPORT_SYMBOL_GPL(mmput);
1114 
1115 #ifdef CONFIG_MMU
1116 static void mmput_async_fn(struct work_struct *work)
1117 {
1118         struct mm_struct *mm = container_of(work, struct mm_struct,
1119                                             async_put_work);
1120 
1121         __mmput(mm);
1122 }
1123 
1124 void mmput_async(struct mm_struct *mm)
1125 {
1126         if (atomic_dec_and_test(&mm->mm_users)) {
1127                 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1128                 schedule_work(&mm->async_put_work);
1129         }
1130 }
1131 #endif
1132 
1133 /**
1134  * set_mm_exe_file - change a reference to the mm's executable file
1135  *
1136  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1137  *
1138  * Main users are mmput() and sys_execve(). Callers prevent concurrent
1139  * invocations: in mmput() nobody alive left, in execve task is single
1140  * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
1141  * mm->exe_file, but does so without using set_mm_exe_file() in order
1142  * to do avoid the need for any locks.
1143  */
1144 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1145 {
1146         struct file *old_exe_file;
1147 
1148         /*
1149          * It is safe to dereference the exe_file without RCU as
1150          * this function is only called if nobody else can access
1151          * this mm -- see comment above for justification.
1152          */
1153         old_exe_file = rcu_dereference_raw(mm->exe_file);
1154 
1155         if (new_exe_file)
1156                 get_file(new_exe_file);
1157         rcu_assign_pointer(mm->exe_file, new_exe_file);
1158         if (old_exe_file)
1159                 fput(old_exe_file);
1160 }
1161 
1162 /**
1163  * get_mm_exe_file - acquire a reference to the mm's executable file
1164  *
1165  * Returns %NULL if mm has no associated executable file.
1166  * User must release file via fput().
1167  */
1168 struct file *get_mm_exe_file(struct mm_struct *mm)
1169 {
1170         struct file *exe_file;
1171 
1172         rcu_read_lock();
1173         exe_file = rcu_dereference(mm->exe_file);
1174         if (exe_file && !get_file_rcu(exe_file))
1175                 exe_file = NULL;
1176         rcu_read_unlock();
1177         return exe_file;
1178 }
1179 EXPORT_SYMBOL(get_mm_exe_file);
1180 
1181 /**
1182  * get_task_exe_file - acquire a reference to the task's executable file
1183  *
1184  * Returns %NULL if task's mm (if any) has no associated executable file or
1185  * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1186  * User must release file via fput().
1187  */
1188 struct file *get_task_exe_file(struct task_struct *task)
1189 {
1190         struct file *exe_file = NULL;
1191         struct mm_struct *mm;
1192 
1193         task_lock(task);
1194         mm = task->mm;
1195         if (mm) {
1196                 if (!(task->flags & PF_KTHREAD))
1197                         exe_file = get_mm_exe_file(mm);
1198         }
1199         task_unlock(task);
1200         return exe_file;
1201 }
1202 EXPORT_SYMBOL(get_task_exe_file);
1203 
1204 /**
1205  * get_task_mm - acquire a reference to the task's mm
1206  *
1207  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
1208  * this kernel workthread has transiently adopted a user mm with use_mm,
1209  * to do its AIO) is not set and if so returns a reference to it, after
1210  * bumping up the use count.  User must release the mm via mmput()
1211  * after use.  Typically used by /proc and ptrace.
1212  */
1213 struct mm_struct *get_task_mm(struct task_struct *task)
1214 {
1215         struct mm_struct *mm;
1216 
1217         task_lock(task);
1218         mm = task->mm;
1219         if (mm) {
1220                 if (task->flags & PF_KTHREAD)
1221                         mm = NULL;
1222                 else
1223                         mmget(mm);
1224         }
1225         task_unlock(task);
1226         return mm;
1227 }
1228 EXPORT_SYMBOL_GPL(get_task_mm);
1229 
1230 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1231 {
1232         struct mm_struct *mm;
1233         int err;
1234 
1235         err =  down_read_killable(&task->signal->exec_update_lock);
1236         if (err)
1237                 return ERR_PTR(err);
1238 
1239         mm = get_task_mm(task);
1240         if (mm && mm != current->mm &&
1241                         !ptrace_may_access(task, mode)) {
1242                 mmput(mm);
1243                 mm = ERR_PTR(-EACCES);
1244         }
1245         up_read(&task->signal->exec_update_lock);
1246 
1247         return mm;
1248 }
1249 
1250 static void complete_vfork_done(struct task_struct *tsk)
1251 {
1252         struct completion *vfork;
1253 
1254         task_lock(tsk);
1255         vfork = tsk->vfork_done;
1256         if (likely(vfork)) {
1257                 tsk->vfork_done = NULL;
1258                 complete(vfork);
1259         }
1260         task_unlock(tsk);
1261 }
1262 
1263 static int wait_for_vfork_done(struct task_struct *child,
1264                                 struct completion *vfork)
1265 {
1266         int killed;
1267 
1268         freezer_do_not_count();
1269         cgroup_enter_frozen();
1270         killed = wait_for_completion_killable(vfork);
1271         cgroup_leave_frozen(false);
1272         freezer_count();
1273 
1274         if (killed) {
1275                 task_lock(child);
1276                 child->vfork_done = NULL;
1277                 task_unlock(child);
1278         }
1279 
1280         put_task_struct(child);
1281         return killed;
1282 }
1283 
1284 /* Please note the differences between mmput and mm_release.
1285  * mmput is called whenever we stop holding onto a mm_struct,
1286  * error success whatever.
1287  *
1288  * mm_release is called after a mm_struct has been removed
1289  * from the current process.
1290  *
1291  * This difference is important for error handling, when we
1292  * only half set up a mm_struct for a new process and need to restore
1293  * the old one.  Because we mmput the new mm_struct before
1294  * restoring the old one. . .
1295  * Eric Biederman 10 January 1998
1296  */
1297 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1298 {
1299         uprobe_free_utask(tsk);
1300 
1301         /* Get rid of any cached register state */
1302         deactivate_mm(tsk, mm);
1303 
1304         /*
1305          * Signal userspace if we're not exiting with a core dump
1306          * because we want to leave the value intact for debugging
1307          * purposes.
1308          */
1309         if (tsk->clear_child_tid) {
1310                 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1311                     atomic_read(&mm->mm_users) > 1) {
1312                         /*
1313                          * We don't check the error code - if userspace has
1314                          * not set up a proper pointer then tough luck.
1315                          */
1316                         put_user(0, tsk->clear_child_tid);
1317                         do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1318                                         1, NULL, NULL, 0, 0);
1319                 }
1320                 tsk->clear_child_tid = NULL;
1321         }
1322 
1323         /*
1324          * All done, finally we can wake up parent and return this mm to him.
1325          * Also kthread_stop() uses this completion for synchronization.
1326          */
1327         if (tsk->vfork_done)
1328                 complete_vfork_done(tsk);
1329 }
1330 
1331 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1332 {
1333         futex_exit_release(tsk);
1334         mm_release(tsk, mm);
1335 }
1336 
1337 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1338 {
1339         futex_exec_release(tsk);
1340         mm_release(tsk, mm);
1341 }
1342 
1343 /**
1344  * dup_mm() - duplicates an existing mm structure
1345  * @tsk: the task_struct with which the new mm will be associated.
1346  * @oldmm: the mm to duplicate.
1347  *
1348  * Allocates a new mm structure and duplicates the provided @oldmm structure
1349  * content into it.
1350  *
1351  * Return: the duplicated mm or NULL on failure.
1352  */
1353 static struct mm_struct *dup_mm(struct task_struct *tsk,
1354                                 struct mm_struct *oldmm)
1355 {
1356         struct mm_struct *mm;
1357         int err;
1358 
1359         mm = allocate_mm();
1360         if (!mm)
1361                 goto fail_nomem;
1362 
1363         memcpy(mm, oldmm, sizeof(*mm));
1364 
1365         if (!mm_init(mm, tsk, mm->user_ns))
1366                 goto fail_nomem;
1367 
1368         err = dup_mmap(mm, oldmm);
1369         if (err)
1370                 goto free_pt;
1371 
1372         mm->hiwater_rss = get_mm_rss(mm);
1373         mm->hiwater_vm = mm->total_vm;
1374 
1375         if (mm->binfmt && !try_module_get(mm->binfmt->module))
1376                 goto free_pt;
1377 
1378         return mm;
1379 
1380 free_pt:
1381         /* don't put binfmt in mmput, we haven't got module yet */
1382         mm->binfmt = NULL;
1383         mm_init_owner(mm, NULL);
1384         mmput(mm);
1385 
1386 fail_nomem:
1387         return NULL;
1388 }
1389 
1390 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1391 {
1392         struct mm_struct *mm, *oldmm;
1393         int retval;
1394 
1395         tsk->min_flt = tsk->maj_flt = 0;
1396         tsk->nvcsw = tsk->nivcsw = 0;
1397 #ifdef CONFIG_DETECT_HUNG_TASK
1398         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1399         tsk->last_switch_time = 0;
1400 #endif
1401 
1402         tsk->mm = NULL;
1403         tsk->active_mm = NULL;
1404 
1405         /*
1406          * Are we cloning a kernel thread?
1407          *
1408          * We need to steal a active VM for that..
1409          */
1410         oldmm = current->mm;
1411         if (!oldmm)
1412                 return 0;
1413 
1414         /* initialize the new vmacache entries */
1415         vmacache_flush(tsk);
1416 
1417         if (clone_flags & CLONE_VM) {
1418                 mmget(oldmm);
1419                 mm = oldmm;
1420                 goto good_mm;
1421         }
1422 
1423         retval = -ENOMEM;
1424         mm = dup_mm(tsk, current->mm);
1425         if (!mm)
1426                 goto fail_nomem;
1427 
1428 good_mm:
1429         tsk->mm = mm;
1430         tsk->active_mm = mm;
1431         return 0;
1432 
1433 fail_nomem:
1434         return retval;
1435 }
1436 
1437 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1438 {
1439         struct fs_struct *fs = current->fs;
1440         if (clone_flags & CLONE_FS) {
1441                 /* tsk->fs is already what we want */
1442                 spin_lock(&fs->lock);
1443                 if (fs->in_exec) {
1444                         spin_unlock(&fs->lock);
1445                         return -EAGAIN;
1446                 }
1447                 fs->users++;
1448                 spin_unlock(&fs->lock);
1449                 return 0;
1450         }
1451         tsk->fs = copy_fs_struct(fs);
1452         if (!tsk->fs)
1453                 return -ENOMEM;
1454         return 0;
1455 }
1456 
1457 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1458 {
1459         struct files_struct *oldf, *newf;
1460         int error = 0;
1461 
1462         /*
1463          * A background process may not have any files ...
1464          */
1465         oldf = current->files;
1466         if (!oldf)
1467                 goto out;
1468 
1469         if (clone_flags & CLONE_FILES) {
1470                 atomic_inc(&oldf->count);
1471                 goto out;
1472         }
1473 
1474         newf = dup_fd(oldf, NR_OPEN_MAX, &error);
1475         if (!newf)
1476                 goto out;
1477 
1478         tsk->files = newf;
1479         error = 0;
1480 out:
1481         return error;
1482 }
1483 
1484 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1485 {
1486 #ifdef CONFIG_BLOCK
1487         struct io_context *ioc = current->io_context;
1488         struct io_context *new_ioc;
1489 
1490         if (!ioc)
1491                 return 0;
1492         /*
1493          * Share io context with parent, if CLONE_IO is set
1494          */
1495         if (clone_flags & CLONE_IO) {
1496                 ioc_task_link(ioc);
1497                 tsk->io_context = ioc;
1498         } else if (ioprio_valid(ioc->ioprio)) {
1499                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1500                 if (unlikely(!new_ioc))
1501                         return -ENOMEM;
1502 
1503                 new_ioc->ioprio = ioc->ioprio;
1504                 put_io_context(new_ioc);
1505         }
1506 #endif
1507         return 0;
1508 }
1509 
1510 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1511 {
1512         struct sighand_struct *sig;
1513 
1514         if (clone_flags & CLONE_SIGHAND) {
1515                 refcount_inc(&current->sighand->count);
1516                 return 0;
1517         }
1518         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1519         RCU_INIT_POINTER(tsk->sighand, sig);
1520         if (!sig)
1521                 return -ENOMEM;
1522 
1523         refcount_set(&sig->count, 1);
1524         spin_lock_irq(&current->sighand->siglock);
1525         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1526         spin_unlock_irq(&current->sighand->siglock);
1527 
1528         /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
1529         if (clone_flags & CLONE_CLEAR_SIGHAND)
1530                 flush_signal_handlers(tsk, 0);
1531 
1532         return 0;
1533 }
1534 
1535 void __cleanup_sighand(struct sighand_struct *sighand)
1536 {
1537         if (refcount_dec_and_test(&sighand->count)) {
1538                 signalfd_cleanup(sighand);
1539                 /*
1540                  * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1541                  * without an RCU grace period, see __lock_task_sighand().
1542                  */
1543                 kmem_cache_free(sighand_cachep, sighand);
1544         }
1545 }
1546 
1547 /*
1548  * Initialize POSIX timer handling for a thread group.
1549  */
1550 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1551 {
1552         struct posix_cputimers *pct = &sig->posix_cputimers;
1553         unsigned long cpu_limit;
1554 
1555         cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1556         posix_cputimers_group_init(pct, cpu_limit);
1557 }
1558 
1559 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1560 {
1561         struct signal_struct *sig;
1562 
1563         if (clone_flags & CLONE_THREAD)
1564                 return 0;
1565 
1566         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1567         tsk->signal = sig;
1568         if (!sig)
1569                 return -ENOMEM;
1570 
1571         sig->nr_threads = 1;
1572         atomic_set(&sig->live, 1);
1573         refcount_set(&sig->sigcnt, 1);
1574 
1575         /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1576         sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1577         tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1578 
1579         init_waitqueue_head(&sig->wait_chldexit);
1580         sig->curr_target = tsk;
1581         init_sigpending(&sig->shared_pending);
1582         INIT_HLIST_HEAD(&sig->multiprocess);
1583         seqlock_init(&sig->stats_lock);
1584         prev_cputime_init(&sig->prev_cputime);
1585 
1586 #ifdef CONFIG_POSIX_TIMERS
1587         INIT_LIST_HEAD(&sig->posix_timers);
1588         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1589         sig->real_timer.function = it_real_fn;
1590 #endif
1591 
1592         task_lock(current->group_leader);
1593         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1594         task_unlock(current->group_leader);
1595 
1596         posix_cpu_timers_init_group(sig);
1597 
1598         tty_audit_fork(sig);
1599         sched_autogroup_fork(sig);
1600 
1601         sig->oom_score_adj = current->signal->oom_score_adj;
1602         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1603 
1604         mutex_init(&sig->cred_guard_mutex);
1605         init_rwsem(&sig->exec_update_lock);
1606 
1607         return 0;
1608 }
1609 
1610 static void copy_seccomp(struct task_struct *p)
1611 {
1612 #ifdef CONFIG_SECCOMP
1613         /*
1614          * Must be called with sighand->lock held, which is common to
1615          * all threads in the group. Holding cred_guard_mutex is not
1616          * needed because this new task is not yet running and cannot
1617          * be racing exec.
1618          */
1619         assert_spin_locked(&current->sighand->siglock);
1620 
1621         /* Ref-count the new filter user, and assign it. */
1622         get_seccomp_filter(current);
1623         p->seccomp = current->seccomp;
1624 
1625         /*
1626          * Explicitly enable no_new_privs here in case it got set
1627          * between the task_struct being duplicated and holding the
1628          * sighand lock. The seccomp state and nnp must be in sync.
1629          */
1630         if (task_no_new_privs(current))
1631                 task_set_no_new_privs(p);
1632 
1633         /*
1634          * If the parent gained a seccomp mode after copying thread
1635          * flags and between before we held the sighand lock, we have
1636          * to manually enable the seccomp thread flag here.
1637          */
1638         if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1639                 set_task_syscall_work(p, SECCOMP);
1640 #endif
1641 }
1642 
1643 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1644 {
1645         current->clear_child_tid = tidptr;
1646 
1647         return task_pid_vnr(current);
1648 }
1649 
1650 static void rt_mutex_init_task(struct task_struct *p)
1651 {
1652         raw_spin_lock_init(&p->pi_lock);
1653 #ifdef CONFIG_RT_MUTEXES
1654         p->pi_waiters = RB_ROOT_CACHED;
1655         p->pi_top_task = NULL;
1656         p->pi_blocked_on = NULL;
1657 #endif
1658 }
1659 
1660 static inline void init_task_pid_links(struct task_struct *task)
1661 {
1662         enum pid_type type;
1663 
1664         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type)
1665                 INIT_HLIST_NODE(&task->pid_links[type]);
1666 }
1667 
1668 static inline void
1669 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1670 {
1671         if (type == PIDTYPE_PID)
1672                 task->thread_pid = pid;
1673         else
1674                 task->signal->pids[type] = pid;
1675 }
1676 
1677 static inline void rcu_copy_process(struct task_struct *p)
1678 {
1679 #ifdef CONFIG_PREEMPT_RCU
1680         p->rcu_read_lock_nesting = 0;
1681         p->rcu_read_unlock_special.s = 0;
1682         p->rcu_blocked_node = NULL;
1683         INIT_LIST_HEAD(&p->rcu_node_entry);
1684 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1685 #ifdef CONFIG_TASKS_RCU
1686         p->rcu_tasks_holdout = false;
1687         INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1688         p->rcu_tasks_idle_cpu = -1;
1689 #endif /* #ifdef CONFIG_TASKS_RCU */
1690 #ifdef CONFIG_TASKS_TRACE_RCU
1691         p->trc_reader_nesting = 0;
1692         p->trc_reader_special.s = 0;
1693         INIT_LIST_HEAD(&p->trc_holdout_list);
1694 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
1695 }
1696 
1697 struct pid *pidfd_pid(const struct file *file)
1698 {
1699         if (file->f_op == &pidfd_fops)
1700                 return file->private_data;
1701 
1702         return ERR_PTR(-EBADF);
1703 }
1704 
1705 static int pidfd_release(struct inode *inode, struct file *file)
1706 {
1707         struct pid *pid = file->private_data;
1708 
1709         file->private_data = NULL;
1710         put_pid(pid);
1711         return 0;
1712 }
1713 
1714 #ifdef CONFIG_PROC_FS
1715 /**
1716  * pidfd_show_fdinfo - print information about a pidfd
1717  * @m: proc fdinfo file
1718  * @f: file referencing a pidfd
1719  *
1720  * Pid:
1721  * This function will print the pid that a given pidfd refers to in the
1722  * pid namespace of the procfs instance.
1723  * If the pid namespace of the process is not a descendant of the pid
1724  * namespace of the procfs instance 0 will be shown as its pid. This is
1725  * similar to calling getppid() on a process whose parent is outside of
1726  * its pid namespace.
1727  *
1728  * NSpid:
1729  * If pid namespaces are supported then this function will also print
1730  * the pid of a given pidfd refers to for all descendant pid namespaces
1731  * starting from the current pid namespace of the instance, i.e. the
1732  * Pid field and the first entry in the NSpid field will be identical.
1733  * If the pid namespace of the process is not a descendant of the pid
1734  * namespace of the procfs instance 0 will be shown as its first NSpid
1735  * entry and no others will be shown.
1736  * Note that this differs from the Pid and NSpid fields in
1737  * /proc/<pid>/status where Pid and NSpid are always shown relative to
1738  * the  pid namespace of the procfs instance. The difference becomes
1739  * obvious when sending around a pidfd between pid namespaces from a
1740  * different branch of the tree, i.e. where no ancestoral relation is
1741  * present between the pid namespaces:
1742  * - create two new pid namespaces ns1 and ns2 in the initial pid
1743  *   namespace (also take care to create new mount namespaces in the
1744  *   new pid namespace and mount procfs)
1745  * - create a process with a pidfd in ns1
1746  * - send pidfd from ns1 to ns2
1747  * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
1748  *   have exactly one entry, which is 0
1749  */
1750 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1751 {
1752         struct pid *pid = f->private_data;
1753         struct pid_namespace *ns;
1754         pid_t nr = -1;
1755 
1756         if (likely(pid_has_task(pid, PIDTYPE_PID))) {
1757                 ns = proc_pid_ns(file_inode(m->file)->i_sb);
1758                 nr = pid_nr_ns(pid, ns);
1759         }
1760 
1761         seq_put_decimal_ll(m, "Pid:\t", nr);
1762 
1763 #ifdef CONFIG_PID_NS
1764         seq_put_decimal_ll(m, "\nNSpid:\t", nr);
1765         if (nr > 0) {
1766                 int i;
1767 
1768                 /* If nr is non-zero it means that 'pid' is valid and that
1769                  * ns, i.e. the pid namespace associated with the procfs
1770                  * instance, is in the pid namespace hierarchy of pid.
1771                  * Start at one below the already printed level.
1772                  */
1773                 for (i = ns->level + 1; i <= pid->level; i++)
1774                         seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
1775         }
1776 #endif
1777         seq_putc(m, '\n');
1778 }
1779 #endif
1780 
1781 /*
1782  * Poll support for process exit notification.
1783  */
1784 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1785 {
1786         struct pid *pid = file->private_data;
1787         __poll_t poll_flags = 0;
1788 
1789         poll_wait(file, &pid->wait_pidfd, pts);
1790 
1791         /*
1792          * Inform pollers only when the whole thread group exits.
1793          * If the thread group leader exits before all other threads in the
1794          * group, then poll(2) should block, similar to the wait(2) family.
1795          */
1796         if (thread_group_exited(pid))
1797                 poll_flags = EPOLLIN | EPOLLRDNORM;
1798 
1799         return poll_flags;
1800 }
1801 
1802 const struct file_operations pidfd_fops = {
1803         .release = pidfd_release,
1804         .poll = pidfd_poll,
1805 #ifdef CONFIG_PROC_FS
1806         .show_fdinfo = pidfd_show_fdinfo,
1807 #endif
1808 };
1809 
1810 static void __delayed_free_task(struct rcu_head *rhp)
1811 {
1812         struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1813 
1814         free_task(tsk);
1815 }
1816 
1817 static __always_inline void delayed_free_task(struct task_struct *tsk)
1818 {
1819         if (IS_ENABLED(CONFIG_MEMCG))
1820                 call_rcu(&tsk->rcu, __delayed_free_task);
1821         else
1822                 free_task(tsk);
1823 }
1824 
1825 static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
1826 {
1827         /* Skip if kernel thread */
1828         if (!tsk->mm)
1829                 return;
1830 
1831         /* Skip if spawning a thread or using vfork */
1832         if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
1833                 return;
1834 
1835         /* We need to synchronize with __set_oom_adj */
1836         mutex_lock(&oom_adj_mutex);
1837         set_bit(MMF_MULTIPROCESS, &tsk->mm->flags);
1838         /* Update the values in case they were changed after copy_signal */
1839         tsk->signal->oom_score_adj = current->signal->oom_score_adj;
1840         tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
1841         mutex_unlock(&oom_adj_mutex);
1842 }
1843 
1844 /*
1845  * This creates a new process as a copy of the old one,
1846  * but does not actually start it yet.
1847  *
1848  * It copies the registers, and all the appropriate
1849  * parts of the process environment (as per the clone
1850  * flags). The actual kick-off is left to the caller.
1851  */
1852 static __latent_entropy struct task_struct *copy_process(
1853                                         struct pid *pid,
1854                                         int trace,
1855                                         int node,
1856                                         struct kernel_clone_args *args)
1857 {
1858         int pidfd = -1, retval;
1859         struct task_struct *p;
1860         struct multiprocess_signals delayed;
1861         struct file *pidfile = NULL;
1862         u64 clone_flags = args->flags;
1863         struct nsproxy *nsp = current->nsproxy;
1864 
1865         /*
1866          * Don't allow sharing the root directory with processes in a different
1867          * namespace
1868          */
1869         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1870                 return ERR_PTR(-EINVAL);
1871 
1872         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1873                 return ERR_PTR(-EINVAL);
1874 
1875         /*
1876          * Thread groups must share signals as well, and detached threads
1877          * can only be started up within the thread group.
1878          */
1879         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1880                 return ERR_PTR(-EINVAL);
1881 
1882         /*
1883          * Shared signal handlers imply shared VM. By way of the above,
1884          * thread groups also imply shared VM. Blocking this case allows
1885          * for various simplifications in other code.
1886          */
1887         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1888                 return ERR_PTR(-EINVAL);
1889 
1890         /*
1891          * Siblings of global init remain as zombies on exit since they are
1892          * not reaped by their parent (swapper). To solve this and to avoid
1893          * multi-rooted process trees, prevent global and container-inits
1894          * from creating siblings.
1895          */
1896         if ((clone_flags & CLONE_PARENT) &&
1897                                 current->signal->flags & SIGNAL_UNKILLABLE)
1898                 return ERR_PTR(-EINVAL);
1899 
1900         /*
1901          * If the new process will be in a different pid or user namespace
1902          * do not allow it to share a thread group with the forking task.
1903          */
1904         if (clone_flags & CLONE_THREAD) {
1905                 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1906                     (task_active_pid_ns(current) != nsp->pid_ns_for_children))
1907                         return ERR_PTR(-EINVAL);
1908         }
1909 
1910         /*
1911          * If the new process will be in a different time namespace
1912          * do not allow it to share VM or a thread group with the forking task.
1913          */
1914         if (clone_flags & (CLONE_THREAD | CLONE_VM)) {
1915                 if (nsp->time_ns != nsp->time_ns_for_children)
1916                         return ERR_PTR(-EINVAL);
1917         }
1918 
1919         if (clone_flags & CLONE_PIDFD) {
1920                 /*
1921                  * - CLONE_DETACHED is blocked so that we can potentially
1922                  *   reuse it later for CLONE_PIDFD.
1923                  * - CLONE_THREAD is blocked until someone really needs it.
1924                  */
1925                 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
1926                         return ERR_PTR(-EINVAL);
1927         }
1928 
1929         /*
1930          * Force any signals received before this point to be delivered
1931          * before the fork happens.  Collect up signals sent to multiple
1932          * processes that happen during the fork and delay them so that
1933          * they appear to happen after the fork.
1934          */
1935         sigemptyset(&delayed.signal);
1936         INIT_HLIST_NODE(&delayed.node);
1937 
1938         spin_lock_irq(&current->sighand->siglock);
1939         if (!(clone_flags & CLONE_THREAD))
1940                 hlist_add_head(&delayed.node, &current->signal->multiprocess);
1941         recalc_sigpending();
1942         spin_unlock_irq(&current->sighand->siglock);
1943         retval = -ERESTARTNOINTR;
1944         if (signal_pending(current))
1945                 goto fork_out;
1946 
1947         retval = -ENOMEM;
1948         p = dup_task_struct(current, node);
1949         if (!p)
1950                 goto fork_out;
1951         if (args->io_thread) {
1952                 /*
1953                  * Mark us an IO worker, and block any signal that isn't
1954                  * fatal or STOP
1955                  */
1956                 p->flags |= PF_IO_WORKER;
1957                 siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
1958         }
1959 
1960         /*
1961          * This _must_ happen before we call free_task(), i.e. before we jump
1962          * to any of the bad_fork_* labels. This is to avoid freeing
1963          * p->set_child_tid which is (ab)used as a kthread's data pointer for
1964          * kernel threads (PF_KTHREAD).
1965          */
1966         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
1967         /*
1968          * Clear TID on mm_release()?
1969          */
1970         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
1971 
1972         ftrace_graph_init_task(p);
1973 
1974         rt_mutex_init_task(p);
1975 
1976         lockdep_assert_irqs_enabled();
1977 #ifdef CONFIG_PROVE_LOCKING
1978         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1979 #endif
1980         retval = -EAGAIN;
1981         if (atomic_read(&p->real_cred->user->processes) >=
1982                         task_rlimit(p, RLIMIT_NPROC)) {
1983                 if (p->real_cred->user != INIT_USER &&
1984                     !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1985                         goto bad_fork_free;
1986         }
1987         current->flags &= ~PF_NPROC_EXCEEDED;
1988 
1989         retval = copy_creds(p, clone_flags);
1990         if (retval < 0)
1991                 goto bad_fork_free;
1992 
1993         /*
1994          * If multiple threads are within copy_process(), then this check
1995          * triggers too late. This doesn't hurt, the check is only there
1996          * to stop root fork bombs.
1997          */
1998         retval = -EAGAIN;
1999         if (data_race(nr_threads >= max_threads))
2000                 goto bad_fork_cleanup_count;
2001 
2002         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
2003         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE | PF_NO_SETAFFINITY);
2004         p->flags |= PF_FORKNOEXEC;
2005         INIT_LIST_HEAD(&p->children);
2006         INIT_LIST_HEAD(&p->sibling);
2007         rcu_copy_process(p);
2008         p->vfork_done = NULL;
2009         spin_lock_init(&p->alloc_lock);
2010 
2011         init_sigpending(&p->pending);
2012 
2013         p->utime = p->stime = p->gtime = 0;
2014 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
2015         p->utimescaled = p->stimescaled = 0;
2016 #endif
2017         prev_cputime_init(&p->prev_cputime);
2018 
2019 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
2020         seqcount_init(&p->vtime.seqcount);
2021         p->vtime.starttime = 0;
2022         p->vtime.state = VTIME_INACTIVE;
2023 #endif
2024 
2025 #ifdef CONFIG_IO_URING
2026         p->io_uring = NULL;
2027 #endif
2028 
2029 #if defined(SPLIT_RSS_COUNTING)
2030         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
2031 #endif
2032 
2033         p->default_timer_slack_ns = current->timer_slack_ns;
2034 
2035 #ifdef CONFIG_PSI
2036         p->psi_flags = 0;
2037 #endif
2038 
2039         task_io_accounting_init(&p->ioac);
2040         acct_clear_integrals(p);
2041 
2042         posix_cputimers_init(&p->posix_cputimers);
2043 
2044         p->io_context = NULL;
2045         audit_set_context(p, NULL);
2046         cgroup_fork(p);
2047 #ifdef CONFIG_NUMA
2048         p->mempolicy = mpol_dup(p->mempolicy);
2049         if (IS_ERR(p->mempolicy)) {
2050                 retval = PTR_ERR(p->mempolicy);
2051                 p->mempolicy = NULL;
2052                 goto bad_fork_cleanup_threadgroup_lock;
2053         }
2054 #endif
2055 #ifdef CONFIG_CPUSETS
2056         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
2057         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
2058         seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
2059 #endif
2060 #ifdef CONFIG_TRACE_IRQFLAGS
2061         memset(&p->irqtrace, 0, sizeof(p->irqtrace));
2062         p->irqtrace.hardirq_disable_ip  = _THIS_IP_;
2063         p->irqtrace.softirq_enable_ip   = _THIS_IP_;
2064         p->softirqs_enabled             = 1;
2065         p->softirq_context              = 0;
2066 #endif
2067 
2068         p->pagefault_disabled = 0;
2069 
2070 #ifdef CONFIG_LOCKDEP
2071         lockdep_init_task(p);
2072 #endif
2073 
2074 #ifdef CONFIG_DEBUG_MUTEXES
2075         p->blocked_on = NULL; /* not blocked yet */
2076 #endif
2077 #ifdef CONFIG_BCACHE
2078         p->sequential_io        = 0;
2079         p->sequential_io_avg    = 0;
2080 #endif
2081 
2082         /* Perform scheduler related setup. Assign this task to a CPU. */
2083         retval = sched_fork(clone_flags, p);
2084         if (retval)
2085                 goto bad_fork_cleanup_policy;
2086 
2087         retval = perf_event_init_task(p);
2088         if (retval)
2089                 goto bad_fork_cleanup_policy;
2090         retval = audit_alloc(p);
2091         if (retval)
2092                 goto bad_fork_cleanup_perf;
2093         /* copy all the process information */
2094         shm_init_task(p);
2095         retval = security_task_alloc(p, clone_flags);
2096         if (retval)
2097                 goto bad_fork_cleanup_audit;
2098         retval = copy_semundo(clone_flags, p);
2099         if (retval)
2100                 goto bad_fork_cleanup_security;
2101         retval = copy_files(clone_flags, p);
2102         if (retval)
2103                 goto bad_fork_cleanup_semundo;
2104         retval = copy_fs(clone_flags, p);
2105         if (retval)
2106                 goto bad_fork_cleanup_files;
2107         retval = copy_sighand(clone_flags, p);
2108         if (retval)
2109                 goto bad_fork_cleanup_fs;
2110         retval = copy_signal(clone_flags, p);
2111         if (retval)
2112                 goto bad_fork_cleanup_sighand;
2113         retval = copy_mm(clone_flags, p);
2114         if (retval)
2115                 goto bad_fork_cleanup_signal;
2116         retval = copy_namespaces(clone_flags, p);
2117         if (retval)
2118                 goto bad_fork_cleanup_mm;
2119         retval = copy_io(clone_flags, p);
2120         if (retval)
2121                 goto bad_fork_cleanup_namespaces;
2122         retval = copy_thread(clone_flags, args->stack, args->stack_size, p, args->tls);
2123         if (retval)
2124                 goto bad_fork_cleanup_io;
2125 
2126         stackleak_task_init(p);
2127 
2128         if (pid != &init_struct_pid) {
2129                 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
2130                                 args->set_tid_size);
2131                 if (IS_ERR(pid)) {
2132                         retval = PTR_ERR(pid);
2133                         goto bad_fork_cleanup_thread;
2134                 }
2135         }
2136 
2137         /*
2138          * This has to happen after we've potentially unshared the file
2139          * descriptor table (so that the pidfd doesn't leak into the child
2140          * if the fd table isn't shared).
2141          */
2142         if (clone_flags & CLONE_PIDFD) {
2143                 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2144                 if (retval < 0)
2145                         goto bad_fork_free_pid;
2146 
2147                 pidfd = retval;
2148 
2149                 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2150                                               O_RDWR | O_CLOEXEC);
2151                 if (IS_ERR(pidfile)) {
2152                         put_unused_fd(pidfd);
2153                         retval = PTR_ERR(pidfile);
2154                         goto bad_fork_free_pid;
2155                 }
2156                 get_pid(pid);   /* held by pidfile now */
2157 
2158                 retval = put_user(pidfd, args->pidfd);
2159                 if (retval)
2160                         goto bad_fork_put_pidfd;
2161         }
2162 
2163 #ifdef CONFIG_BLOCK
2164         p->plug = NULL;
2165 #endif
2166         futex_init_task(p);
2167 
2168         /*
2169          * sigaltstack should be cleared when sharing the same VM
2170          */
2171         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2172                 sas_ss_reset(p);
2173 
2174         /*
2175          * Syscall tracing and stepping should be turned off in the
2176          * child regardless of CLONE_PTRACE.
2177          */
2178         user_disable_single_step(p);
2179         clear_task_syscall_work(p, SYSCALL_TRACE);
2180 #if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU)
2181         clear_task_syscall_work(p, SYSCALL_EMU);
2182 #endif
2183         clear_tsk_latency_tracing(p);
2184 
2185         /* ok, now we should be set up.. */
2186         p->pid = pid_nr(pid);
2187         if (clone_flags & CLONE_THREAD) {
2188                 p->group_leader = current->group_leader;
2189                 p->tgid = current->tgid;
2190         } else {
2191                 p->group_leader = p;
2192                 p->tgid = p->pid;
2193         }
2194 
2195         p->nr_dirtied = 0;
2196         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2197         p->dirty_paused_when = 0;
2198 
2199         p->pdeath_signal = 0;
2200         INIT_LIST_HEAD(&p->thread_group);
2201         p->task_works = NULL;
2202 
2203 #ifdef CONFIG_KRETPROBES
2204         p->kretprobe_instances.first = NULL;
2205 #endif
2206 
2207         /*
2208          * Ensure that the cgroup subsystem policies allow the new process to be
2209          * forked. It should be noted that the new process's css_set can be changed
2210          * between here and cgroup_post_fork() if an organisation operation is in
2211          * progress.
2212          */
2213         retval = cgroup_can_fork(p, args);
2214         if (retval)
2215                 goto bad_fork_put_pidfd;
2216 
2217         /*
2218          * From this point on we must avoid any synchronous user-space
2219          * communication until we take the tasklist-lock. In particular, we do
2220          * not want user-space to be able to predict the process start-time by
2221          * stalling fork(2) after we recorded the start_time but before it is
2222          * visible to the system.
2223          */
2224 
2225         p->start_time = ktime_get_ns();
2226         p->start_boottime = ktime_get_boottime_ns();
2227 
2228         /*
2229          * Make it visible to the rest of the system, but dont wake it up yet.
2230          * Need tasklist lock for parent etc handling!
2231          */
2232         write_lock_irq(&tasklist_lock);
2233 
2234         /* CLONE_PARENT re-uses the old parent */
2235         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2236                 p->real_parent = current->real_parent;
2237                 p->parent_exec_id = current->parent_exec_id;
2238                 if (clone_flags & CLONE_THREAD)
2239                         p->exit_signal = -1;
2240                 else
2241                         p->exit_signal = current->group_leader->exit_signal;
2242         } else {
2243                 p->real_parent = current;
2244                 p->parent_exec_id = current->self_exec_id;
2245                 p->exit_signal = args->exit_signal;
2246         }
2247 
2248         klp_copy_process(p);
2249 
2250         spin_lock(&current->sighand->siglock);
2251 
2252         /*
2253          * Copy seccomp details explicitly here, in case they were changed
2254          * before holding sighand lock.
2255          */
2256         copy_seccomp(p);
2257 
2258         rseq_fork(p, clone_flags);
2259 
2260         /* Don't start children in a dying pid namespace */
2261         if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2262                 retval = -ENOMEM;
2263                 goto bad_fork_cancel_cgroup;
2264         }
2265 
2266         /* Let kill terminate clone/fork in the middle */
2267         if (fatal_signal_pending(current)) {
2268                 retval = -EINTR;
2269                 goto bad_fork_cancel_cgroup;
2270         }
2271 
2272         /* past the last point of failure */
2273         if (pidfile)
2274                 fd_install(pidfd, pidfile);
2275 
2276         init_task_pid_links(p);
2277         if (likely(p->pid)) {
2278                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2279 
2280                 init_task_pid(p, PIDTYPE_PID, pid);
2281                 if (thread_group_leader(p)) {
2282                         init_task_pid(p, PIDTYPE_TGID, pid);
2283                         init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2284                         init_task_pid(p, PIDTYPE_SID, task_session(current));
2285 
2286                         if (is_child_reaper(pid)) {
2287                                 ns_of_pid(pid)->child_reaper = p;
2288                                 p->signal->flags |= SIGNAL_UNKILLABLE;
2289                         }
2290                         p->signal->shared_pending.signal = delayed.signal;
2291                         p->signal->tty = tty_kref_get(current->signal->tty);
2292                         /*
2293                          * Inherit has_child_subreaper flag under the same
2294                          * tasklist_lock with adding child to the process tree
2295                          * for propagate_has_child_subreaper optimization.
2296                          */
2297                         p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2298                                                          p->real_parent->signal->is_child_subreaper;
2299                         list_add_tail(&p->sibling, &p->real_parent->children);
2300                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
2301                         attach_pid(p, PIDTYPE_TGID);
2302                         attach_pid(p, PIDTYPE_PGID);
2303                         attach_pid(p, PIDTYPE_SID);
2304                         __this_cpu_inc(process_counts);
2305                 } else {
2306                         current->signal->nr_threads++;
2307                         atomic_inc(&current->signal->live);
2308                         refcount_inc(&current->signal->sigcnt);
2309                         task_join_group_stop(p);
2310                         list_add_tail_rcu(&p->thread_group,
2311                                           &p->group_leader->thread_group);
2312                         list_add_tail_rcu(&p->thread_node,
2313                                           &p->signal->thread_head);
2314                 }
2315                 attach_pid(p, PIDTYPE_PID);
2316                 nr_threads++;
2317         }
2318         total_forks++;
2319         hlist_del_init(&delayed.node);
2320         spin_unlock(&current->sighand->siglock);
2321         syscall_tracepoint_update(p);
2322         write_unlock_irq(&tasklist_lock);
2323 
2324         proc_fork_connector(p);
2325         sched_post_fork(p);
2326         cgroup_post_fork(p, args);
2327         perf_event_fork(p);
2328 
2329         trace_task_newtask(p, clone_flags);
2330         uprobe_copy_process(p, clone_flags);
2331 
2332         copy_oom_score_adj(clone_flags, p);
2333 
2334         return p;
2335 
2336 bad_fork_cancel_cgroup:
2337         spin_unlock(&current->sighand->siglock);
2338         write_unlock_irq(&tasklist_lock);
2339         cgroup_cancel_fork(p, args);
2340 bad_fork_put_pidfd:
2341         if (clone_flags & CLONE_PIDFD) {
2342                 fput(pidfile);
2343                 put_unused_fd(pidfd);
2344         }
2345 bad_fork_free_pid:
2346         if (pid != &init_struct_pid)
2347                 free_pid(pid);
2348 bad_fork_cleanup_thread:
2349         exit_thread(p);
2350 bad_fork_cleanup_io:
2351         if (p->io_context)
2352                 exit_io_context(p);
2353 bad_fork_cleanup_namespaces:
2354         exit_task_namespaces(p);
2355 bad_fork_cleanup_mm:
2356         if (p->mm) {
2357                 mm_clear_owner(p->mm, p);
2358                 mmput(p->mm);
2359         }
2360 bad_fork_cleanup_signal:
2361         if (!(clone_flags & CLONE_THREAD))
2362                 free_signal_struct(p->signal);
2363 bad_fork_cleanup_sighand:
2364         __cleanup_sighand(p->sighand);
2365 bad_fork_cleanup_fs:
2366         exit_fs(p); /* blocking */
2367 bad_fork_cleanup_files:
2368         exit_files(p); /* blocking */
2369 bad_fork_cleanup_semundo:
2370         exit_sem(p);
2371 bad_fork_cleanup_security:
2372         security_task_free(p);
2373 bad_fork_cleanup_audit:
2374         audit_free(p);
2375 bad_fork_cleanup_perf:
2376         perf_event_free_task(p);
2377 bad_fork_cleanup_policy:
2378         lockdep_free_task(p);
2379 #ifdef CONFIG_NUMA
2380         mpol_put(p->mempolicy);
2381 bad_fork_cleanup_threadgroup_lock:
2382 #endif
2383         delayacct_tsk_free(p);
2384 bad_fork_cleanup_count:
2385         atomic_dec(&p->cred->user->processes);
2386         exit_creds(p);
2387 bad_fork_free:
2388         p->state = TASK_DEAD;
2389         put_task_stack(p);
2390         delayed_free_task(p);
2391 fork_out:
2392         spin_lock_irq(&current->sighand->siglock);
2393         hlist_del_init(&delayed.node);
2394         spin_unlock_irq(&current->sighand->siglock);
2395         return ERR_PTR(retval);
2396 }
2397 
2398 static inline void init_idle_pids(struct task_struct *idle)
2399 {
2400         enum pid_type type;
2401 
2402         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2403                 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2404                 init_task_pid(idle, type, &init_struct_pid);
2405         }
2406 }
2407 
2408 struct task_struct * __init fork_idle(int cpu)
2409 {
2410         struct task_struct *task;
2411         struct kernel_clone_args args = {
2412                 .flags = CLONE_VM,
2413         };
2414 
2415         task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2416         if (!IS_ERR(task)) {
2417                 init_idle_pids(task);
2418                 init_idle(task, cpu);
2419         }
2420 
2421         return task;
2422 }
2423 
2424 struct mm_struct *copy_init_mm(void)
2425 {
2426         return dup_mm(NULL, &init_mm);
2427 }
2428 
2429 /*
2430  * This is like kernel_clone(), but shaved down and tailored to just
2431  * creating io_uring workers. It returns a created task, or an error pointer.
2432  * The returned task is inactive, and the caller must fire it up through
2433  * wake_up_new_task(p). All signals are blocked in the created task.
2434  */
2435 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
2436 {
2437         unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|
2438                                 CLONE_IO;
2439         struct kernel_clone_args args = {
2440                 .flags          = ((lower_32_bits(flags) | CLONE_VM |
2441                                     CLONE_UNTRACED) & ~CSIGNAL),
2442                 .exit_signal    = (lower_32_bits(flags) & CSIGNAL),
2443                 .stack          = (unsigned long)fn,
2444                 .stack_size     = (unsigned long)arg,
2445                 .io_thread      = 1,
2446         };
2447 
2448         return copy_process(NULL, 0, node, &args);
2449 }
2450 
2451 /*
2452  *  Ok, this is the main fork-routine.
2453  *
2454  * It copies the process, and if successful kick-starts
2455  * it and waits for it to finish using the VM if required.
2456  *
2457  * args->exit_signal is expected to be checked for sanity by the caller.
2458  */
2459 pid_t kernel_clone(struct kernel_clone_args *args)
2460 {
2461         u64 clone_flags = args->flags;
2462         struct completion vfork;
2463         struct pid *pid;
2464         struct task_struct *p;
2465         int trace = 0;
2466         pid_t nr;
2467 
2468         /*
2469          * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
2470          * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
2471          * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
2472          * field in struct clone_args and it still doesn't make sense to have
2473          * them both point at the same memory location. Performing this check
2474          * here has the advantage that we don't need to have a separate helper
2475          * to check for legacy clone().
2476          */
2477         if ((args->flags & CLONE_PIDFD) &&
2478             (args->flags & CLONE_PARENT_SETTID) &&
2479             (args->pidfd == args->parent_tid))
2480                 return -EINVAL;
2481 
2482         /*
2483          * Determine whether and which event to report to ptracer.  When
2484          * called from kernel_thread or CLONE_UNTRACED is explicitly
2485          * requested, no event is reported; otherwise, report if the event
2486          * for the type of forking is enabled.
2487          */
2488         if (!(clone_flags & CLONE_UNTRACED)) {
2489                 if (clone_flags & CLONE_VFORK)
2490                         trace = PTRACE_EVENT_VFORK;
2491                 else if (args->exit_signal != SIGCHLD)
2492                         trace = PTRACE_EVENT_CLONE;
2493                 else
2494                         trace = PTRACE_EVENT_FORK;
2495 
2496                 if (likely(!ptrace_event_enabled(current, trace)))
2497                         trace = 0;
2498         }
2499 
2500         p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2501         add_latent_entropy();
2502 
2503         if (IS_ERR(p))
2504                 return PTR_ERR(p);
2505 
2506         /*
2507          * Do this prior waking up the new thread - the thread pointer
2508          * might get invalid after that point, if the thread exits quickly.
2509          */
2510         trace_sched_process_fork(current, p);
2511 
2512         pid = get_task_pid(p, PIDTYPE_PID);
2513         nr = pid_vnr(pid);
2514 
2515         if (clone_flags & CLONE_PARENT_SETTID)
2516                 put_user(nr, args->parent_tid);
2517 
2518         if (clone_flags & CLONE_VFORK) {
2519                 p->vfork_done = &vfork;
2520                 init_completion(&vfork);
2521                 get_task_struct(p);
2522         }
2523 
2524         wake_up_new_task(p);
2525 
2526         /* forking complete and child started to run, tell ptracer */
2527         if (unlikely(trace))
2528                 ptrace_event_pid(trace, pid);
2529 
2530         if (clone_flags & CLONE_VFORK) {
2531                 if (!wait_for_vfork_done(p, &vfork))
2532                         ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2533         }
2534 
2535         put_pid(pid);
2536         return nr;
2537 }
2538 
2539 /*
2540  * Create a kernel thread.
2541  */
2542 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2543 {
2544         struct kernel_clone_args args = {
2545                 .flags          = ((lower_32_bits(flags) | CLONE_VM |
2546                                     CLONE_UNTRACED) & ~CSIGNAL),
2547                 .exit_signal    = (lower_32_bits(flags) & CSIGNAL),
2548                 .stack          = (unsigned long)fn,
2549                 .stack_size     = (unsigned long)arg,
2550         };
2551 
2552         return kernel_clone(&args);
2553 }
2554 
2555 #ifdef __ARCH_WANT_SYS_FORK
2556 SYSCALL_DEFINE0(fork)
2557 {
2558 #ifdef CONFIG_MMU
2559         struct kernel_clone_args args = {
2560                 .exit_signal = SIGCHLD,
2561         };
2562 
2563         return kernel_clone(&args);
2564 #else
2565         /* can not support in nommu mode */
2566         return -EINVAL;
2567 #endif
2568 }
2569 #endif
2570 
2571 #ifdef __ARCH_WANT_SYS_VFORK
2572 SYSCALL_DEFINE0(vfork)
2573 {
2574         struct kernel_clone_args args = {
2575                 .flags          = CLONE_VFORK | CLONE_VM,
2576                 .exit_signal    = SIGCHLD,
2577         };
2578 
2579         return kernel_clone(&args);
2580 }
2581 #endif
2582 
2583 #ifdef __ARCH_WANT_SYS_CLONE
2584 #ifdef CONFIG_CLONE_BACKWARDS
2585 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2586                  int __user *, parent_tidptr,
2587                  unsigned long, tls,
2588                  int __user *, child_tidptr)
2589 #elif defined(CONFIG_CLONE_BACKWARDS2)
2590 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2591                  int __user *, parent_tidptr,
2592                  int __user *, child_tidptr,
2593                  unsigned long, tls)
2594 #elif defined(CONFIG_CLONE_BACKWARDS3)
2595 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2596                 int, stack_size,
2597                 int __user *, parent_tidptr,
2598                 int __user *, child_tidptr,
2599                 unsigned long, tls)
2600 #else
2601 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2602                  int __user *, parent_tidptr,
2603                  int __user *, child_tidptr,
2604                  unsigned long, tls)
2605 #endif
2606 {
2607         struct kernel_clone_args args = {
2608                 .flags          = (lower_32_bits(clone_flags) & ~CSIGNAL),
2609                 .pidfd          = parent_tidptr,
2610                 .child_tid      = child_tidptr,
2611                 .parent_tid     = parent_tidptr,
2612                 .exit_signal    = (lower_32_bits(clone_flags) & CSIGNAL),
2613                 .stack          = newsp,
2614                 .tls            = tls,
2615         };
2616 
2617         return kernel_clone(&args);
2618 }
2619 #endif
2620 
2621 #ifdef __ARCH_WANT_SYS_CLONE3
2622 
2623 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2624                                               struct clone_args __user *uargs,
2625                                               size_t usize)
2626 {
2627         int err;
2628         struct clone_args args;
2629         pid_t *kset_tid = kargs->set_tid;
2630 
2631         BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
2632                      CLONE_ARGS_SIZE_VER0);
2633         BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
2634                      CLONE_ARGS_SIZE_VER1);
2635         BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
2636                      CLONE_ARGS_SIZE_VER2);
2637         BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
2638 
2639         if (unlikely(usize > PAGE_SIZE))
2640                 return -E2BIG;
2641         if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2642                 return -EINVAL;
2643 
2644         err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2645         if (err)
2646                 return err;
2647 
2648         if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
2649                 return -EINVAL;
2650 
2651         if (unlikely(!args.set_tid && args.set_tid_size > 0))
2652                 return -EINVAL;
2653 
2654         if (unlikely(args.set_tid && args.set_tid_size == 0))
2655                 return -EINVAL;
2656 
2657         /*
2658          * Verify that higher 32bits of exit_signal are unset and that
2659          * it is a valid signal
2660          */
2661         if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2662                      !valid_signal(args.exit_signal)))
2663                 return -EINVAL;
2664 
2665         if ((args.flags & CLONE_INTO_CGROUP) &&
2666             (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
2667                 return -EINVAL;
2668 
2669         *kargs = (struct kernel_clone_args){
2670                 .flags          = args.flags,
2671                 .pidfd          = u64_to_user_ptr(args.pidfd),
2672                 .child_tid      = u64_to_user_ptr(args.child_tid),
2673                 .parent_tid     = u64_to_user_ptr(args.parent_tid),
2674                 .exit_signal    = args.exit_signal,
2675                 .stack          = args.stack,
2676                 .stack_size     = args.stack_size,
2677                 .tls            = args.tls,
2678                 .set_tid_size   = args.set_tid_size,
2679                 .cgroup         = args.cgroup,
2680         };
2681 
2682         if (args.set_tid &&
2683                 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
2684                         (kargs->set_tid_size * sizeof(pid_t))))
2685                 return -EFAULT;
2686 
2687         kargs->set_tid = kset_tid;
2688 
2689         return 0;
2690 }
2691 
2692 /**
2693  * clone3_stack_valid - check and prepare stack
2694  * @kargs: kernel clone args
2695  *
2696  * Verify that the stack arguments userspace gave us are sane.
2697  * In addition, set the stack direction for userspace since it's easy for us to
2698  * determine.
2699  */
2700 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2701 {
2702         if (kargs->stack == 0) {
2703                 if (kargs->stack_size > 0)
2704                         return false;
2705         } else {
2706                 if (kargs->stack_size == 0)
2707                         return false;
2708 
2709                 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2710                         return false;
2711 
2712 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2713                 kargs->stack += kargs->stack_size;
2714 #endif
2715         }
2716 
2717         return true;
2718 }
2719 
2720 static bool clone3_args_valid(struct kernel_clone_args *kargs)
2721 {
2722         /* Verify that no unknown flags are passed along. */
2723         if (kargs->flags &
2724             ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
2725                 return false;
2726 
2727         /*
2728          * - make the CLONE_DETACHED bit reuseable for clone3
2729          * - make the CSIGNAL bits reuseable for clone3
2730          */
2731         if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2732                 return false;
2733 
2734         if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
2735             (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
2736                 return false;
2737 
2738         if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2739             kargs->exit_signal)
2740                 return false;
2741 
2742         if (!clone3_stack_valid(kargs))
2743                 return false;
2744 
2745         return true;
2746 }
2747 
2748 /**
2749  * clone3 - create a new process with specific properties
2750  * @uargs: argument structure
2751  * @size:  size of @uargs
2752  *
2753  * clone3() is the extensible successor to clone()/clone2().
2754  * It takes a struct as argument that is versioned by its size.
2755  *
2756  * Return: On success, a positive PID for the child process.
2757  *         On error, a negative errno number.
2758  */
2759 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2760 {
2761         int err;
2762 
2763         struct kernel_clone_args kargs;
2764         pid_t set_tid[MAX_PID_NS_LEVEL];
2765 
2766         kargs.set_tid = set_tid;
2767 
2768         err = copy_clone_args_from_user(&kargs, uargs, size);
2769         if (err)
2770                 return err;
2771 
2772         if (!clone3_args_valid(&kargs))
2773                 return -EINVAL;
2774 
2775         return kernel_clone(&kargs);
2776 }
2777 #endif
2778 
2779 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2780 {
2781         struct task_struct *leader, *parent, *child;
2782         int res;
2783 
2784         read_lock(&tasklist_lock);
2785         leader = top = top->group_leader;
2786 down:
2787         for_each_thread(leader, parent) {
2788                 list_for_each_entry(child, &parent->children, sibling) {
2789                         res = visitor(child, data);
2790                         if (res) {
2791                                 if (res < 0)
2792                                         goto out;
2793                                 leader = child;
2794                                 goto down;
2795                         }
2796 up:
2797                         ;
2798                 }
2799         }
2800 
2801         if (leader != top) {
2802                 child = leader;
2803                 parent = child->real_parent;
2804                 leader = parent->group_leader;
2805                 goto up;
2806         }
2807 out:
2808         read_unlock(&tasklist_lock);
2809 }
2810 
2811 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2812 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2813 #endif
2814 
2815 static void sighand_ctor(void *data)
2816 {
2817         struct sighand_struct *sighand = data;
2818 
2819         spin_lock_init(&sighand->siglock);
2820         init_waitqueue_head(&sighand->signalfd_wqh);
2821 }
2822 
2823 void __init proc_caches_init(void)
2824 {
2825         unsigned int mm_size;
2826 
2827         sighand_cachep = kmem_cache_create("sighand_cache",
2828                         sizeof(struct sighand_struct), 0,
2829                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2830                         SLAB_ACCOUNT, sighand_ctor);
2831         signal_cachep = kmem_cache_create("signal_cache",
2832                         sizeof(struct signal_struct), 0,
2833                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2834                         NULL);
2835         files_cachep = kmem_cache_create("files_cache",
2836                         sizeof(struct files_struct), 0,
2837                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2838                         NULL);
2839         fs_cachep = kmem_cache_create("fs_cache",
2840                         sizeof(struct fs_struct), 0,
2841                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2842                         NULL);
2843 
2844         /*
2845          * The mm_cpumask is located at the end of mm_struct, and is
2846          * dynamically sized based on the maximum CPU number this system
2847          * can have, taking hotplug into account (nr_cpu_ids).
2848          */
2849         mm_size = sizeof(struct mm_struct) + cpumask_size();
2850 
2851         mm_cachep = kmem_cache_create_usercopy("mm_struct",
2852                         mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2853                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2854                         offsetof(struct mm_struct, saved_auxv),
2855                         sizeof_field(struct mm_struct, saved_auxv),
2856                         NULL);
2857         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2858         mmap_init();
2859         nsproxy_cache_init();
2860 }
2861 
2862 /*
2863  * Check constraints on flags passed to the unshare system call.
2864  */
2865 static int check_unshare_flags(unsigned long unshare_flags)
2866 {
2867         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2868                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2869                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2870                                 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
2871                                 CLONE_NEWTIME))
2872                 return -EINVAL;
2873         /*
2874          * Not implemented, but pretend it works if there is nothing
2875          * to unshare.  Note that unsharing the address space or the
2876          * signal handlers also need to unshare the signal queues (aka
2877          * CLONE_THREAD).
2878          */
2879         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2880                 if (!thread_group_empty(current))
2881                         return -EINVAL;
2882         }
2883         if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2884                 if (refcount_read(&current->sighand->count) > 1)
2885                         return -EINVAL;
2886         }
2887         if (unshare_flags & CLONE_VM) {
2888                 if (!current_is_single_threaded())
2889                         return -EINVAL;
2890         }
2891 
2892         return 0;
2893 }
2894 
2895 /*
2896  * Unshare the filesystem structure if it is being shared
2897  */
2898 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2899 {
2900         struct fs_struct *fs = current->fs;
2901 
2902         if (!(unshare_flags & CLONE_FS) || !fs)
2903                 return 0;
2904 
2905         /* don't need lock here; in the worst case we'll do useless copy */
2906         if (fs->users == 1)
2907                 return 0;
2908 
2909         *new_fsp = copy_fs_struct(fs);
2910         if (!*new_fsp)
2911                 return -ENOMEM;
2912 
2913         return 0;
2914 }
2915 
2916 /*
2917  * Unshare file descriptor table if it is being shared
2918  */
2919 int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
2920                struct files_struct **new_fdp)
2921 {
2922         struct files_struct *fd = current->files;
2923         int error = 0;
2924 
2925         if ((unshare_flags & CLONE_FILES) &&
2926             (fd && atomic_read(&fd->count) > 1)) {
2927                 *new_fdp = dup_fd(fd, max_fds, &error);
2928                 if (!*new_fdp)
2929                         return error;
2930         }
2931 
2932         return 0;
2933 }
2934 
2935 /*
2936  * unshare allows a process to 'unshare' part of the process
2937  * context which was originally shared using clone.  copy_*
2938  * functions used by kernel_clone() cannot be used here directly
2939  * because they modify an inactive task_struct that is being
2940  * constructed. Here we are modifying the current, active,
2941  * task_struct.
2942  */
2943 int ksys_unshare(unsigned long unshare_flags)
2944 {
2945         struct fs_struct *fs, *new_fs = NULL;
2946         struct files_struct *fd, *new_fd = NULL;
2947         struct cred *new_cred = NULL;
2948         struct nsproxy *new_nsproxy = NULL;
2949         int do_sysvsem = 0;
2950         int err;
2951 
2952         /*
2953          * If unsharing a user namespace must also unshare the thread group
2954          * and unshare the filesystem root and working directories.
2955          */
2956         if (unshare_flags & CLONE_NEWUSER)
2957                 unshare_flags |= CLONE_THREAD | CLONE_FS;
2958         /*
2959          * If unsharing vm, must also unshare signal handlers.
2960          */
2961         if (unshare_flags & CLONE_VM)
2962                 unshare_flags |= CLONE_SIGHAND;
2963         /*
2964          * If unsharing a signal handlers, must also unshare the signal queues.
2965          */
2966         if (unshare_flags & CLONE_SIGHAND)
2967                 unshare_flags |= CLONE_THREAD;
2968         /*
2969          * If unsharing namespace, must also unshare filesystem information.
2970          */
2971         if (unshare_flags & CLONE_NEWNS)
2972                 unshare_flags |= CLONE_FS;
2973 
2974         err = check_unshare_flags(unshare_flags);
2975         if (err)
2976                 goto bad_unshare_out;
2977         /*
2978          * CLONE_NEWIPC must also detach from the undolist: after switching
2979          * to a new ipc namespace, the semaphore arrays from the old
2980          * namespace are unreachable.
2981          */
2982         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2983                 do_sysvsem = 1;
2984         err = unshare_fs(unshare_flags, &new_fs);
2985         if (err)
2986                 goto bad_unshare_out;
2987         err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd);
2988         if (err)
2989                 goto bad_unshare_cleanup_fs;
2990         err = unshare_userns(unshare_flags, &new_cred);
2991         if (err)
2992                 goto bad_unshare_cleanup_fd;
2993         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2994                                          new_cred, new_fs);
2995         if (err)
2996                 goto bad_unshare_cleanup_cred;
2997 
2998         if (new_cred) {
2999                 err = set_cred_ucounts(new_cred);
3000                 if (err)
3001                         goto bad_unshare_cleanup_cred;
3002         }
3003 
3004         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
3005                 if (do_sysvsem) {
3006                         /*
3007                          * CLONE_SYSVSEM is equivalent to sys_exit().
3008                          */
3009                         exit_sem(current);
3010                 }
3011                 if (unshare_flags & CLONE_NEWIPC) {
3012                         /* Orphan segments in old ns (see sem above). */
3013                         exit_shm(current);
3014                         shm_init_task(current);
3015                 }
3016 
3017                 if (new_nsproxy)
3018                         switch_task_namespaces(current, new_nsproxy);
3019 
3020                 task_lock(current);
3021 
3022                 if (new_fs) {
3023                         fs = current->fs;
3024                         spin_lock(&fs->lock);
3025                         current->fs = new_fs;
3026                         if (--fs->users)
3027                                 new_fs = NULL;
3028                         else
3029                                 new_fs = fs;
3030                         spin_unlock(&fs->lock);
3031                 }
3032 
3033                 if (new_fd) {
3034                         fd = current->files;
3035                         current->files = new_fd;
3036                         new_fd = fd;
3037                 }
3038 
3039                 task_unlock(current);
3040 
3041                 if (new_cred) {
3042                         /* Install the new user namespace */
3043                         commit_creds(new_cred);
3044                         new_cred = NULL;
3045                 }
3046         }
3047 
3048         perf_event_namespaces(current);
3049 
3050 bad_unshare_cleanup_cred:
3051         if (new_cred)
3052                 put_cred(new_cred);
3053 bad_unshare_cleanup_fd:
3054         if (new_fd)
3055                 put_files_struct(new_fd);
3056 
3057 bad_unshare_cleanup_fs:
3058         if (new_fs)
3059                 free_fs_struct(new_fs);
3060 
3061 bad_unshare_out:
3062         return err;
3063 }
3064 
3065 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
3066 {
3067         return ksys_unshare(unshare_flags);
3068 }
3069 
3070 /*
3071  *      Helper to unshare the files of the current task.
3072  *      We don't want to expose copy_files internals to
3073  *      the exec layer of the kernel.
3074  */
3075 
3076 int unshare_files(void)
3077 {
3078         struct task_struct *task = current;
3079         struct files_struct *old, *copy = NULL;
3080         int error;
3081 
3082         error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, &copy);
3083         if (error || !copy)
3084                 return error;
3085 
3086         old = task->files;
3087         task_lock(task);
3088         task->files = copy;
3089         task_unlock(task);
3090         put_files_struct(old);
3091         return 0;
3092 }
3093 
3094 int sysctl_max_threads(struct ctl_table *table, int write,
3095                        void *buffer, size_t *lenp, loff_t *ppos)
3096 {
3097         struct ctl_table t;
3098         int ret;
3099         int threads = max_threads;
3100         int min = 1;
3101         int max = MAX_THREADS;
3102 
3103         t = *table;
3104         t.data = &threads;
3105         t.extra1 = &min;
3106         t.extra2 = &max;
3107 
3108         ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3109         if (ret || !write)
3110                 return ret;
3111 
3112         max_threads = threads;
3113 
3114         return 0;
3115 }
3116 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp