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TOMOYO Linux Cross Reference
Linux/fs/exec.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  *  linux/fs/exec.c
  4  *
  5  *  Copyright (C) 1991, 1992  Linus Torvalds
  6  */
  7 
  8 /*
  9  * #!-checking implemented by tytso.
 10  */
 11 /*
 12  * Demand-loading implemented 01.12.91 - no need to read anything but
 13  * the header into memory. The inode of the executable is put into
 14  * "current->executable", and page faults do the actual loading. Clean.
 15  *
 16  * Once more I can proudly say that linux stood up to being changed: it
 17  * was less than 2 hours work to get demand-loading completely implemented.
 18  *
 19  * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
 20  * current->executable is only used by the procfs.  This allows a dispatch
 21  * table to check for several different types  of binary formats.  We keep
 22  * trying until we recognize the file or we run out of supported binary
 23  * formats.
 24  */
 25 
 26 #include <linux/kernel_read_file.h>
 27 #include <linux/slab.h>
 28 #include <linux/file.h>
 29 #include <linux/fdtable.h>
 30 #include <linux/mm.h>
 31 #include <linux/vmacache.h>
 32 #include <linux/stat.h>
 33 #include <linux/fcntl.h>
 34 #include <linux/swap.h>
 35 #include <linux/string.h>
 36 #include <linux/init.h>
 37 #include <linux/sched/mm.h>
 38 #include <linux/sched/coredump.h>
 39 #include <linux/sched/signal.h>
 40 #include <linux/sched/numa_balancing.h>
 41 #include <linux/sched/task.h>
 42 #include <linux/pagemap.h>
 43 #include <linux/perf_event.h>
 44 #include <linux/highmem.h>
 45 #include <linux/spinlock.h>
 46 #include <linux/key.h>
 47 #include <linux/personality.h>
 48 #include <linux/binfmts.h>
 49 #include <linux/utsname.h>
 50 #include <linux/pid_namespace.h>
 51 #include <linux/module.h>
 52 #include <linux/namei.h>
 53 #include <linux/mount.h>
 54 #include <linux/security.h>
 55 #include <linux/syscalls.h>
 56 #include <linux/tsacct_kern.h>
 57 #include <linux/cn_proc.h>
 58 #include <linux/audit.h>
 59 #include <linux/tracehook.h>
 60 #include <linux/kmod.h>
 61 #include <linux/fsnotify.h>
 62 #include <linux/fs_struct.h>
 63 #include <linux/oom.h>
 64 #include <linux/compat.h>
 65 #include <linux/vmalloc.h>
 66 #include <linux/io_uring.h>
 67 #include <linux/syscall_user_dispatch.h>
 68 
 69 #include <linux/uaccess.h>
 70 #include <asm/mmu_context.h>
 71 #include <asm/tlb.h>
 72 
 73 #include <trace/events/task.h>
 74 #include "internal.h"
 75 
 76 #include <trace/events/sched.h>
 77 
 78 static int bprm_creds_from_file(struct linux_binprm *bprm);
 79 
 80 int suid_dumpable = 0;
 81 
 82 static LIST_HEAD(formats);
 83 static DEFINE_RWLOCK(binfmt_lock);
 84 
 85 void __register_binfmt(struct linux_binfmt * fmt, int insert)
 86 {
 87         BUG_ON(!fmt);
 88         if (WARN_ON(!fmt->load_binary))
 89                 return;
 90         write_lock(&binfmt_lock);
 91         insert ? list_add(&fmt->lh, &formats) :
 92                  list_add_tail(&fmt->lh, &formats);
 93         write_unlock(&binfmt_lock);
 94 }
 95 
 96 EXPORT_SYMBOL(__register_binfmt);
 97 
 98 void unregister_binfmt(struct linux_binfmt * fmt)
 99 {
100         write_lock(&binfmt_lock);
101         list_del(&fmt->lh);
102         write_unlock(&binfmt_lock);
103 }
104 
105 EXPORT_SYMBOL(unregister_binfmt);
106 
107 static inline void put_binfmt(struct linux_binfmt * fmt)
108 {
109         module_put(fmt->module);
110 }
111 
112 bool path_noexec(const struct path *path)
113 {
114         return (path->mnt->mnt_flags & MNT_NOEXEC) ||
115                (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
116 }
117 
118 #ifdef CONFIG_USELIB
119 /*
120  * Note that a shared library must be both readable and executable due to
121  * security reasons.
122  *
123  * Also note that we take the address to load from from the file itself.
124  */
125 SYSCALL_DEFINE1(uselib, const char __user *, library)
126 {
127         struct linux_binfmt *fmt;
128         struct file *file;
129         struct filename *tmp = getname(library);
130         int error = PTR_ERR(tmp);
131         static const struct open_flags uselib_flags = {
132                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
133                 .acc_mode = MAY_READ | MAY_EXEC,
134                 .intent = LOOKUP_OPEN,
135                 .lookup_flags = LOOKUP_FOLLOW,
136         };
137 
138         if (IS_ERR(tmp))
139                 goto out;
140 
141         file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
142         putname(tmp);
143         error = PTR_ERR(file);
144         if (IS_ERR(file))
145                 goto out;
146 
147         /*
148          * may_open() has already checked for this, so it should be
149          * impossible to trip now. But we need to be extra cautious
150          * and check again at the very end too.
151          */
152         error = -EACCES;
153         if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
154                          path_noexec(&file->f_path)))
155                 goto exit;
156 
157         fsnotify_open(file);
158 
159         error = -ENOEXEC;
160 
161         read_lock(&binfmt_lock);
162         list_for_each_entry(fmt, &formats, lh) {
163                 if (!fmt->load_shlib)
164                         continue;
165                 if (!try_module_get(fmt->module))
166                         continue;
167                 read_unlock(&binfmt_lock);
168                 error = fmt->load_shlib(file);
169                 read_lock(&binfmt_lock);
170                 put_binfmt(fmt);
171                 if (error != -ENOEXEC)
172                         break;
173         }
174         read_unlock(&binfmt_lock);
175 exit:
176         fput(file);
177 out:
178         return error;
179 }
180 #endif /* #ifdef CONFIG_USELIB */
181 
182 #ifdef CONFIG_MMU
183 /*
184  * The nascent bprm->mm is not visible until exec_mmap() but it can
185  * use a lot of memory, account these pages in current->mm temporary
186  * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
187  * change the counter back via acct_arg_size(0).
188  */
189 static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
190 {
191         struct mm_struct *mm = current->mm;
192         long diff = (long)(pages - bprm->vma_pages);
193 
194         if (!mm || !diff)
195                 return;
196 
197         bprm->vma_pages = pages;
198         add_mm_counter(mm, MM_ANONPAGES, diff);
199 }
200 
201 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
202                 int write)
203 {
204         struct page *page;
205         int ret;
206         unsigned int gup_flags = FOLL_FORCE;
207 
208 #ifdef CONFIG_STACK_GROWSUP
209         if (write) {
210                 ret = expand_downwards(bprm->vma, pos);
211                 if (ret < 0)
212                         return NULL;
213         }
214 #endif
215 
216         if (write)
217                 gup_flags |= FOLL_WRITE;
218 
219         /*
220          * We are doing an exec().  'current' is the process
221          * doing the exec and bprm->mm is the new process's mm.
222          */
223         ret = get_user_pages_remote(bprm->mm, pos, 1, gup_flags,
224                         &page, NULL, NULL);
225         if (ret <= 0)
226                 return NULL;
227 
228         if (write)
229                 acct_arg_size(bprm, vma_pages(bprm->vma));
230 
231         return page;
232 }
233 
234 static void put_arg_page(struct page *page)
235 {
236         put_page(page);
237 }
238 
239 static void free_arg_pages(struct linux_binprm *bprm)
240 {
241 }
242 
243 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
244                 struct page *page)
245 {
246         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
247 }
248 
249 static int __bprm_mm_init(struct linux_binprm *bprm)
250 {
251         int err;
252         struct vm_area_struct *vma = NULL;
253         struct mm_struct *mm = bprm->mm;
254 
255         bprm->vma = vma = vm_area_alloc(mm);
256         if (!vma)
257                 return -ENOMEM;
258         vma_set_anonymous(vma);
259 
260         if (mmap_write_lock_killable(mm)) {
261                 err = -EINTR;
262                 goto err_free;
263         }
264 
265         /*
266          * Place the stack at the largest stack address the architecture
267          * supports. Later, we'll move this to an appropriate place. We don't
268          * use STACK_TOP because that can depend on attributes which aren't
269          * configured yet.
270          */
271         BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
272         vma->vm_end = STACK_TOP_MAX;
273         vma->vm_start = vma->vm_end - PAGE_SIZE;
274         vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
275         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
276 
277         err = insert_vm_struct(mm, vma);
278         if (err)
279                 goto err;
280 
281         mm->stack_vm = mm->total_vm = 1;
282         mmap_write_unlock(mm);
283         bprm->p = vma->vm_end - sizeof(void *);
284         return 0;
285 err:
286         mmap_write_unlock(mm);
287 err_free:
288         bprm->vma = NULL;
289         vm_area_free(vma);
290         return err;
291 }
292 
293 static bool valid_arg_len(struct linux_binprm *bprm, long len)
294 {
295         return len <= MAX_ARG_STRLEN;
296 }
297 
298 #else
299 
300 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
301 {
302 }
303 
304 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
305                 int write)
306 {
307         struct page *page;
308 
309         page = bprm->page[pos / PAGE_SIZE];
310         if (!page && write) {
311                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
312                 if (!page)
313                         return NULL;
314                 bprm->page[pos / PAGE_SIZE] = page;
315         }
316 
317         return page;
318 }
319 
320 static void put_arg_page(struct page *page)
321 {
322 }
323 
324 static void free_arg_page(struct linux_binprm *bprm, int i)
325 {
326         if (bprm->page[i]) {
327                 __free_page(bprm->page[i]);
328                 bprm->page[i] = NULL;
329         }
330 }
331 
332 static void free_arg_pages(struct linux_binprm *bprm)
333 {
334         int i;
335 
336         for (i = 0; i < MAX_ARG_PAGES; i++)
337                 free_arg_page(bprm, i);
338 }
339 
340 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
341                 struct page *page)
342 {
343 }
344 
345 static int __bprm_mm_init(struct linux_binprm *bprm)
346 {
347         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
348         return 0;
349 }
350 
351 static bool valid_arg_len(struct linux_binprm *bprm, long len)
352 {
353         return len <= bprm->p;
354 }
355 
356 #endif /* CONFIG_MMU */
357 
358 /*
359  * Create a new mm_struct and populate it with a temporary stack
360  * vm_area_struct.  We don't have enough context at this point to set the stack
361  * flags, permissions, and offset, so we use temporary values.  We'll update
362  * them later in setup_arg_pages().
363  */
364 static int bprm_mm_init(struct linux_binprm *bprm)
365 {
366         int err;
367         struct mm_struct *mm = NULL;
368 
369         bprm->mm = mm = mm_alloc();
370         err = -ENOMEM;
371         if (!mm)
372                 goto err;
373 
374         /* Save current stack limit for all calculations made during exec. */
375         task_lock(current->group_leader);
376         bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK];
377         task_unlock(current->group_leader);
378 
379         err = __bprm_mm_init(bprm);
380         if (err)
381                 goto err;
382 
383         return 0;
384 
385 err:
386         if (mm) {
387                 bprm->mm = NULL;
388                 mmdrop(mm);
389         }
390 
391         return err;
392 }
393 
394 struct user_arg_ptr {
395 #ifdef CONFIG_COMPAT
396         bool is_compat;
397 #endif
398         union {
399                 const char __user *const __user *native;
400 #ifdef CONFIG_COMPAT
401                 const compat_uptr_t __user *compat;
402 #endif
403         } ptr;
404 };
405 
406 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
407 {
408         const char __user *native;
409 
410 #ifdef CONFIG_COMPAT
411         if (unlikely(argv.is_compat)) {
412                 compat_uptr_t compat;
413 
414                 if (get_user(compat, argv.ptr.compat + nr))
415                         return ERR_PTR(-EFAULT);
416 
417                 return compat_ptr(compat);
418         }
419 #endif
420 
421         if (get_user(native, argv.ptr.native + nr))
422                 return ERR_PTR(-EFAULT);
423 
424         return native;
425 }
426 
427 /*
428  * count() counts the number of strings in array ARGV.
429  */
430 static int count(struct user_arg_ptr argv, int max)
431 {
432         int i = 0;
433 
434         if (argv.ptr.native != NULL) {
435                 for (;;) {
436                         const char __user *p = get_user_arg_ptr(argv, i);
437 
438                         if (!p)
439                                 break;
440 
441                         if (IS_ERR(p))
442                                 return -EFAULT;
443 
444                         if (i >= max)
445                                 return -E2BIG;
446                         ++i;
447 
448                         if (fatal_signal_pending(current))
449                                 return -ERESTARTNOHAND;
450                         cond_resched();
451                 }
452         }
453         return i;
454 }
455 
456 static int count_strings_kernel(const char *const *argv)
457 {
458         int i;
459 
460         if (!argv)
461                 return 0;
462 
463         for (i = 0; argv[i]; ++i) {
464                 if (i >= MAX_ARG_STRINGS)
465                         return -E2BIG;
466                 if (fatal_signal_pending(current))
467                         return -ERESTARTNOHAND;
468                 cond_resched();
469         }
470         return i;
471 }
472 
473 static int bprm_stack_limits(struct linux_binprm *bprm)
474 {
475         unsigned long limit, ptr_size;
476 
477         /*
478          * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
479          * (whichever is smaller) for the argv+env strings.
480          * This ensures that:
481          *  - the remaining binfmt code will not run out of stack space,
482          *  - the program will have a reasonable amount of stack left
483          *    to work from.
484          */
485         limit = _STK_LIM / 4 * 3;
486         limit = min(limit, bprm->rlim_stack.rlim_cur / 4);
487         /*
488          * We've historically supported up to 32 pages (ARG_MAX)
489          * of argument strings even with small stacks
490          */
491         limit = max_t(unsigned long, limit, ARG_MAX);
492         /*
493          * We must account for the size of all the argv and envp pointers to
494          * the argv and envp strings, since they will also take up space in
495          * the stack. They aren't stored until much later when we can't
496          * signal to the parent that the child has run out of stack space.
497          * Instead, calculate it here so it's possible to fail gracefully.
498          */
499         ptr_size = (bprm->argc + bprm->envc) * sizeof(void *);
500         if (limit <= ptr_size)
501                 return -E2BIG;
502         limit -= ptr_size;
503 
504         bprm->argmin = bprm->p - limit;
505         return 0;
506 }
507 
508 /*
509  * 'copy_strings()' copies argument/environment strings from the old
510  * processes's memory to the new process's stack.  The call to get_user_pages()
511  * ensures the destination page is created and not swapped out.
512  */
513 static int copy_strings(int argc, struct user_arg_ptr argv,
514                         struct linux_binprm *bprm)
515 {
516         struct page *kmapped_page = NULL;
517         char *kaddr = NULL;
518         unsigned long kpos = 0;
519         int ret;
520 
521         while (argc-- > 0) {
522                 const char __user *str;
523                 int len;
524                 unsigned long pos;
525 
526                 ret = -EFAULT;
527                 str = get_user_arg_ptr(argv, argc);
528                 if (IS_ERR(str))
529                         goto out;
530 
531                 len = strnlen_user(str, MAX_ARG_STRLEN);
532                 if (!len)
533                         goto out;
534 
535                 ret = -E2BIG;
536                 if (!valid_arg_len(bprm, len))
537                         goto out;
538 
539                 /* We're going to work our way backwords. */
540                 pos = bprm->p;
541                 str += len;
542                 bprm->p -= len;
543 #ifdef CONFIG_MMU
544                 if (bprm->p < bprm->argmin)
545                         goto out;
546 #endif
547 
548                 while (len > 0) {
549                         int offset, bytes_to_copy;
550 
551                         if (fatal_signal_pending(current)) {
552                                 ret = -ERESTARTNOHAND;
553                                 goto out;
554                         }
555                         cond_resched();
556 
557                         offset = pos % PAGE_SIZE;
558                         if (offset == 0)
559                                 offset = PAGE_SIZE;
560 
561                         bytes_to_copy = offset;
562                         if (bytes_to_copy > len)
563                                 bytes_to_copy = len;
564 
565                         offset -= bytes_to_copy;
566                         pos -= bytes_to_copy;
567                         str -= bytes_to_copy;
568                         len -= bytes_to_copy;
569 
570                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
571                                 struct page *page;
572 
573                                 page = get_arg_page(bprm, pos, 1);
574                                 if (!page) {
575                                         ret = -E2BIG;
576                                         goto out;
577                                 }
578 
579                                 if (kmapped_page) {
580                                         flush_kernel_dcache_page(kmapped_page);
581                                         kunmap(kmapped_page);
582                                         put_arg_page(kmapped_page);
583                                 }
584                                 kmapped_page = page;
585                                 kaddr = kmap(kmapped_page);
586                                 kpos = pos & PAGE_MASK;
587                                 flush_arg_page(bprm, kpos, kmapped_page);
588                         }
589                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
590                                 ret = -EFAULT;
591                                 goto out;
592                         }
593                 }
594         }
595         ret = 0;
596 out:
597         if (kmapped_page) {
598                 flush_kernel_dcache_page(kmapped_page);
599                 kunmap(kmapped_page);
600                 put_arg_page(kmapped_page);
601         }
602         return ret;
603 }
604 
605 /*
606  * Copy and argument/environment string from the kernel to the processes stack.
607  */
608 int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
609 {
610         int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;
611         unsigned long pos = bprm->p;
612 
613         if (len == 0)
614                 return -EFAULT;
615         if (!valid_arg_len(bprm, len))
616                 return -E2BIG;
617 
618         /* We're going to work our way backwards. */
619         arg += len;
620         bprm->p -= len;
621         if (IS_ENABLED(CONFIG_MMU) && bprm->p < bprm->argmin)
622                 return -E2BIG;
623 
624         while (len > 0) {
625                 unsigned int bytes_to_copy = min_t(unsigned int, len,
626                                 min_not_zero(offset_in_page(pos), PAGE_SIZE));
627                 struct page *page;
628                 char *kaddr;
629 
630                 pos -= bytes_to_copy;
631                 arg -= bytes_to_copy;
632                 len -= bytes_to_copy;
633 
634                 page = get_arg_page(bprm, pos, 1);
635                 if (!page)
636                         return -E2BIG;
637                 kaddr = kmap_atomic(page);
638                 flush_arg_page(bprm, pos & PAGE_MASK, page);
639                 memcpy(kaddr + offset_in_page(pos), arg, bytes_to_copy);
640                 flush_kernel_dcache_page(page);
641                 kunmap_atomic(kaddr);
642                 put_arg_page(page);
643         }
644 
645         return 0;
646 }
647 EXPORT_SYMBOL(copy_string_kernel);
648 
649 static int copy_strings_kernel(int argc, const char *const *argv,
650                                struct linux_binprm *bprm)
651 {
652         while (argc-- > 0) {
653                 int ret = copy_string_kernel(argv[argc], bprm);
654                 if (ret < 0)
655                         return ret;
656                 if (fatal_signal_pending(current))
657                         return -ERESTARTNOHAND;
658                 cond_resched();
659         }
660         return 0;
661 }
662 
663 #ifdef CONFIG_MMU
664 
665 /*
666  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
667  * the binfmt code determines where the new stack should reside, we shift it to
668  * its final location.  The process proceeds as follows:
669  *
670  * 1) Use shift to calculate the new vma endpoints.
671  * 2) Extend vma to cover both the old and new ranges.  This ensures the
672  *    arguments passed to subsequent functions are consistent.
673  * 3) Move vma's page tables to the new range.
674  * 4) Free up any cleared pgd range.
675  * 5) Shrink the vma to cover only the new range.
676  */
677 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
678 {
679         struct mm_struct *mm = vma->vm_mm;
680         unsigned long old_start = vma->vm_start;
681         unsigned long old_end = vma->vm_end;
682         unsigned long length = old_end - old_start;
683         unsigned long new_start = old_start - shift;
684         unsigned long new_end = old_end - shift;
685         struct mmu_gather tlb;
686 
687         BUG_ON(new_start > new_end);
688 
689         /*
690          * ensure there are no vmas between where we want to go
691          * and where we are
692          */
693         if (vma != find_vma(mm, new_start))
694                 return -EFAULT;
695 
696         /*
697          * cover the whole range: [new_start, old_end)
698          */
699         if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
700                 return -ENOMEM;
701 
702         /*
703          * move the page tables downwards, on failure we rely on
704          * process cleanup to remove whatever mess we made.
705          */
706         if (length != move_page_tables(vma, old_start,
707                                        vma, new_start, length, false))
708                 return -ENOMEM;
709 
710         lru_add_drain();
711         tlb_gather_mmu(&tlb, mm);
712         if (new_end > old_start) {
713                 /*
714                  * when the old and new regions overlap clear from new_end.
715                  */
716                 free_pgd_range(&tlb, new_end, old_end, new_end,
717                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
718         } else {
719                 /*
720                  * otherwise, clean from old_start; this is done to not touch
721                  * the address space in [new_end, old_start) some architectures
722                  * have constraints on va-space that make this illegal (IA64) -
723                  * for the others its just a little faster.
724                  */
725                 free_pgd_range(&tlb, old_start, old_end, new_end,
726                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
727         }
728         tlb_finish_mmu(&tlb);
729 
730         /*
731          * Shrink the vma to just the new range.  Always succeeds.
732          */
733         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
734 
735         return 0;
736 }
737 
738 /*
739  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
740  * the stack is optionally relocated, and some extra space is added.
741  */
742 int setup_arg_pages(struct linux_binprm *bprm,
743                     unsigned long stack_top,
744                     int executable_stack)
745 {
746         unsigned long ret;
747         unsigned long stack_shift;
748         struct mm_struct *mm = current->mm;
749         struct vm_area_struct *vma = bprm->vma;
750         struct vm_area_struct *prev = NULL;
751         unsigned long vm_flags;
752         unsigned long stack_base;
753         unsigned long stack_size;
754         unsigned long stack_expand;
755         unsigned long rlim_stack;
756 
757 #ifdef CONFIG_STACK_GROWSUP
758         /* Limit stack size */
759         stack_base = bprm->rlim_stack.rlim_max;
760 
761         stack_base = calc_max_stack_size(stack_base);
762 
763         /* Add space for stack randomization. */
764         stack_base += (STACK_RND_MASK << PAGE_SHIFT);
765 
766         /* Make sure we didn't let the argument array grow too large. */
767         if (vma->vm_end - vma->vm_start > stack_base)
768                 return -ENOMEM;
769 
770         stack_base = PAGE_ALIGN(stack_top - stack_base);
771 
772         stack_shift = vma->vm_start - stack_base;
773         mm->arg_start = bprm->p - stack_shift;
774         bprm->p = vma->vm_end - stack_shift;
775 #else
776         stack_top = arch_align_stack(stack_top);
777         stack_top = PAGE_ALIGN(stack_top);
778 
779         if (unlikely(stack_top < mmap_min_addr) ||
780             unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
781                 return -ENOMEM;
782 
783         stack_shift = vma->vm_end - stack_top;
784 
785         bprm->p -= stack_shift;
786         mm->arg_start = bprm->p;
787 #endif
788 
789         if (bprm->loader)
790                 bprm->loader -= stack_shift;
791         bprm->exec -= stack_shift;
792 
793         if (mmap_write_lock_killable(mm))
794                 return -EINTR;
795 
796         vm_flags = VM_STACK_FLAGS;
797 
798         /*
799          * Adjust stack execute permissions; explicitly enable for
800          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
801          * (arch default) otherwise.
802          */
803         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
804                 vm_flags |= VM_EXEC;
805         else if (executable_stack == EXSTACK_DISABLE_X)
806                 vm_flags &= ~VM_EXEC;
807         vm_flags |= mm->def_flags;
808         vm_flags |= VM_STACK_INCOMPLETE_SETUP;
809 
810         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
811                         vm_flags);
812         if (ret)
813                 goto out_unlock;
814         BUG_ON(prev != vma);
815 
816         if (unlikely(vm_flags & VM_EXEC)) {
817                 pr_warn_once("process '%pD4' started with executable stack\n",
818                              bprm->file);
819         }
820 
821         /* Move stack pages down in memory. */
822         if (stack_shift) {
823                 ret = shift_arg_pages(vma, stack_shift);
824                 if (ret)
825                         goto out_unlock;
826         }
827 
828         /* mprotect_fixup is overkill to remove the temporary stack flags */
829         vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
830 
831         stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
832         stack_size = vma->vm_end - vma->vm_start;
833         /*
834          * Align this down to a page boundary as expand_stack
835          * will align it up.
836          */
837         rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK;
838 #ifdef CONFIG_STACK_GROWSUP
839         if (stack_size + stack_expand > rlim_stack)
840                 stack_base = vma->vm_start + rlim_stack;
841         else
842                 stack_base = vma->vm_end + stack_expand;
843 #else
844         if (stack_size + stack_expand > rlim_stack)
845                 stack_base = vma->vm_end - rlim_stack;
846         else
847                 stack_base = vma->vm_start - stack_expand;
848 #endif
849         current->mm->start_stack = bprm->p;
850         ret = expand_stack(vma, stack_base);
851         if (ret)
852                 ret = -EFAULT;
853 
854 out_unlock:
855         mmap_write_unlock(mm);
856         return ret;
857 }
858 EXPORT_SYMBOL(setup_arg_pages);
859 
860 #else
861 
862 /*
863  * Transfer the program arguments and environment from the holding pages
864  * onto the stack. The provided stack pointer is adjusted accordingly.
865  */
866 int transfer_args_to_stack(struct linux_binprm *bprm,
867                            unsigned long *sp_location)
868 {
869         unsigned long index, stop, sp;
870         int ret = 0;
871 
872         stop = bprm->p >> PAGE_SHIFT;
873         sp = *sp_location;
874 
875         for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
876                 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
877                 char *src = kmap(bprm->page[index]) + offset;
878                 sp -= PAGE_SIZE - offset;
879                 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
880                         ret = -EFAULT;
881                 kunmap(bprm->page[index]);
882                 if (ret)
883                         goto out;
884         }
885 
886         *sp_location = sp;
887 
888 out:
889         return ret;
890 }
891 EXPORT_SYMBOL(transfer_args_to_stack);
892 
893 #endif /* CONFIG_MMU */
894 
895 static struct file *do_open_execat(int fd, struct filename *name, int flags)
896 {
897         struct file *file;
898         int err;
899         struct open_flags open_exec_flags = {
900                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
901                 .acc_mode = MAY_EXEC,
902                 .intent = LOOKUP_OPEN,
903                 .lookup_flags = LOOKUP_FOLLOW,
904         };
905 
906         if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
907                 return ERR_PTR(-EINVAL);
908         if (flags & AT_SYMLINK_NOFOLLOW)
909                 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
910         if (flags & AT_EMPTY_PATH)
911                 open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
912 
913         file = do_filp_open(fd, name, &open_exec_flags);
914         if (IS_ERR(file))
915                 goto out;
916 
917         /*
918          * may_open() has already checked for this, so it should be
919          * impossible to trip now. But we need to be extra cautious
920          * and check again at the very end too.
921          */
922         err = -EACCES;
923         if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
924                          path_noexec(&file->f_path)))
925                 goto exit;
926 
927         err = deny_write_access(file);
928         if (err)
929                 goto exit;
930 
931         if (name->name[0] != '\0')
932                 fsnotify_open(file);
933 
934 out:
935         return file;
936 
937 exit:
938         fput(file);
939         return ERR_PTR(err);
940 }
941 
942 struct file *open_exec(const char *name)
943 {
944         struct filename *filename = getname_kernel(name);
945         struct file *f = ERR_CAST(filename);
946 
947         if (!IS_ERR(filename)) {
948                 f = do_open_execat(AT_FDCWD, filename, 0);
949                 putname(filename);
950         }
951         return f;
952 }
953 EXPORT_SYMBOL(open_exec);
954 
955 #if defined(CONFIG_HAVE_AOUT) || defined(CONFIG_BINFMT_FLAT) || \
956     defined(CONFIG_BINFMT_ELF_FDPIC)
957 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
958 {
959         ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
960         if (res > 0)
961                 flush_icache_user_range(addr, addr + len);
962         return res;
963 }
964 EXPORT_SYMBOL(read_code);
965 #endif
966 
967 /*
968  * Maps the mm_struct mm into the current task struct.
969  * On success, this function returns with exec_update_lock
970  * held for writing.
971  */
972 static int exec_mmap(struct mm_struct *mm)
973 {
974         struct task_struct *tsk;
975         struct mm_struct *old_mm, *active_mm;
976         int ret;
977 
978         /* Notify parent that we're no longer interested in the old VM */
979         tsk = current;
980         old_mm = current->mm;
981         exec_mm_release(tsk, old_mm);
982         if (old_mm)
983                 sync_mm_rss(old_mm);
984 
985         ret = down_write_killable(&tsk->signal->exec_update_lock);
986         if (ret)
987                 return ret;
988 
989         if (old_mm) {
990                 /*
991                  * Make sure that if there is a core dump in progress
992                  * for the old mm, we get out and die instead of going
993                  * through with the exec.  We must hold mmap_lock around
994                  * checking core_state and changing tsk->mm.
995                  */
996                 mmap_read_lock(old_mm);
997                 if (unlikely(old_mm->core_state)) {
998                         mmap_read_unlock(old_mm);
999                         up_write(&tsk->signal->exec_update_lock);
1000                         return -EINTR;
1001                 }
1002         }
1003 
1004         task_lock(tsk);
1005         membarrier_exec_mmap(mm);
1006 
1007         local_irq_disable();
1008         active_mm = tsk->active_mm;
1009         tsk->active_mm = mm;
1010         tsk->mm = mm;
1011         /*
1012          * This prevents preemption while active_mm is being loaded and
1013          * it and mm are being updated, which could cause problems for
1014          * lazy tlb mm refcounting when these are updated by context
1015          * switches. Not all architectures can handle irqs off over
1016          * activate_mm yet.
1017          */
1018         if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
1019                 local_irq_enable();
1020         activate_mm(active_mm, mm);
1021         if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
1022                 local_irq_enable();
1023         tsk->mm->vmacache_seqnum = 0;
1024         vmacache_flush(tsk);
1025         task_unlock(tsk);
1026         if (old_mm) {
1027                 mmap_read_unlock(old_mm);
1028                 BUG_ON(active_mm != old_mm);
1029                 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
1030                 mm_update_next_owner(old_mm);
1031                 mmput(old_mm);
1032                 return 0;
1033         }
1034         mmdrop(active_mm);
1035         return 0;
1036 }
1037 
1038 static int de_thread(struct task_struct *tsk)
1039 {
1040         struct signal_struct *sig = tsk->signal;
1041         struct sighand_struct *oldsighand = tsk->sighand;
1042         spinlock_t *lock = &oldsighand->siglock;
1043 
1044         if (thread_group_empty(tsk))
1045                 goto no_thread_group;
1046 
1047         /*
1048          * Kill all other threads in the thread group.
1049          */
1050         spin_lock_irq(lock);
1051         if (signal_group_exit(sig)) {
1052                 /*
1053                  * Another group action in progress, just
1054                  * return so that the signal is processed.
1055                  */
1056                 spin_unlock_irq(lock);
1057                 return -EAGAIN;
1058         }
1059 
1060         sig->group_exit_task = tsk;
1061         sig->notify_count = zap_other_threads(tsk);
1062         if (!thread_group_leader(tsk))
1063                 sig->notify_count--;
1064 
1065         while (sig->notify_count) {
1066                 __set_current_state(TASK_KILLABLE);
1067                 spin_unlock_irq(lock);
1068                 schedule();
1069                 if (__fatal_signal_pending(tsk))
1070                         goto killed;
1071                 spin_lock_irq(lock);
1072         }
1073         spin_unlock_irq(lock);
1074 
1075         /*
1076          * At this point all other threads have exited, all we have to
1077          * do is to wait for the thread group leader to become inactive,
1078          * and to assume its PID:
1079          */
1080         if (!thread_group_leader(tsk)) {
1081                 struct task_struct *leader = tsk->group_leader;
1082 
1083                 for (;;) {
1084                         cgroup_threadgroup_change_begin(tsk);
1085                         write_lock_irq(&tasklist_lock);
1086                         /*
1087                          * Do this under tasklist_lock to ensure that
1088                          * exit_notify() can't miss ->group_exit_task
1089                          */
1090                         sig->notify_count = -1;
1091                         if (likely(leader->exit_state))
1092                                 break;
1093                         __set_current_state(TASK_KILLABLE);
1094                         write_unlock_irq(&tasklist_lock);
1095                         cgroup_threadgroup_change_end(tsk);
1096                         schedule();
1097                         if (__fatal_signal_pending(tsk))
1098                                 goto killed;
1099                 }
1100 
1101                 /*
1102                  * The only record we have of the real-time age of a
1103                  * process, regardless of execs it's done, is start_time.
1104                  * All the past CPU time is accumulated in signal_struct
1105                  * from sister threads now dead.  But in this non-leader
1106                  * exec, nothing survives from the original leader thread,
1107                  * whose birth marks the true age of this process now.
1108                  * When we take on its identity by switching to its PID, we
1109                  * also take its birthdate (always earlier than our own).
1110                  */
1111                 tsk->start_time = leader->start_time;
1112                 tsk->start_boottime = leader->start_boottime;
1113 
1114                 BUG_ON(!same_thread_group(leader, tsk));
1115                 /*
1116                  * An exec() starts a new thread group with the
1117                  * TGID of the previous thread group. Rehash the
1118                  * two threads with a switched PID, and release
1119                  * the former thread group leader:
1120                  */
1121 
1122                 /* Become a process group leader with the old leader's pid.
1123                  * The old leader becomes a thread of the this thread group.
1124                  */
1125                 exchange_tids(tsk, leader);
1126                 transfer_pid(leader, tsk, PIDTYPE_TGID);
1127                 transfer_pid(leader, tsk, PIDTYPE_PGID);
1128                 transfer_pid(leader, tsk, PIDTYPE_SID);
1129 
1130                 list_replace_rcu(&leader->tasks, &tsk->tasks);
1131                 list_replace_init(&leader->sibling, &tsk->sibling);
1132 
1133                 tsk->group_leader = tsk;
1134                 leader->group_leader = tsk;
1135 
1136                 tsk->exit_signal = SIGCHLD;
1137                 leader->exit_signal = -1;
1138 
1139                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1140                 leader->exit_state = EXIT_DEAD;
1141 
1142                 /*
1143                  * We are going to release_task()->ptrace_unlink() silently,
1144                  * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1145                  * the tracer wont't block again waiting for this thread.
1146                  */
1147                 if (unlikely(leader->ptrace))
1148                         __wake_up_parent(leader, leader->parent);
1149                 write_unlock_irq(&tasklist_lock);
1150                 cgroup_threadgroup_change_end(tsk);
1151 
1152                 release_task(leader);
1153         }
1154 
1155         sig->group_exit_task = NULL;
1156         sig->notify_count = 0;
1157 
1158 no_thread_group:
1159         /* we have changed execution domain */
1160         tsk->exit_signal = SIGCHLD;
1161 
1162         BUG_ON(!thread_group_leader(tsk));
1163         return 0;
1164 
1165 killed:
1166         /* protects against exit_notify() and __exit_signal() */
1167         read_lock(&tasklist_lock);
1168         sig->group_exit_task = NULL;
1169         sig->notify_count = 0;
1170         read_unlock(&tasklist_lock);
1171         return -EAGAIN;
1172 }
1173 
1174 
1175 /*
1176  * This function makes sure the current process has its own signal table,
1177  * so that flush_signal_handlers can later reset the handlers without
1178  * disturbing other processes.  (Other processes might share the signal
1179  * table via the CLONE_SIGHAND option to clone().)
1180  */
1181 static int unshare_sighand(struct task_struct *me)
1182 {
1183         struct sighand_struct *oldsighand = me->sighand;
1184 
1185         if (refcount_read(&oldsighand->count) != 1) {
1186                 struct sighand_struct *newsighand;
1187                 /*
1188                  * This ->sighand is shared with the CLONE_SIGHAND
1189                  * but not CLONE_THREAD task, switch to the new one.
1190                  */
1191                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1192                 if (!newsighand)
1193                         return -ENOMEM;
1194 
1195                 refcount_set(&newsighand->count, 1);
1196                 memcpy(newsighand->action, oldsighand->action,
1197                        sizeof(newsighand->action));
1198 
1199                 write_lock_irq(&tasklist_lock);
1200                 spin_lock(&oldsighand->siglock);
1201                 rcu_assign_pointer(me->sighand, newsighand);
1202                 spin_unlock(&oldsighand->siglock);
1203                 write_unlock_irq(&tasklist_lock);
1204 
1205                 __cleanup_sighand(oldsighand);
1206         }
1207         return 0;
1208 }
1209 
1210 char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
1211 {
1212         task_lock(tsk);
1213         strncpy(buf, tsk->comm, buf_size);
1214         task_unlock(tsk);
1215         return buf;
1216 }
1217 EXPORT_SYMBOL_GPL(__get_task_comm);
1218 
1219 /*
1220  * These functions flushes out all traces of the currently running executable
1221  * so that a new one can be started
1222  */
1223 
1224 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1225 {
1226         task_lock(tsk);
1227         trace_task_rename(tsk, buf);
1228         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1229         task_unlock(tsk);
1230         perf_event_comm(tsk, exec);
1231 }
1232 
1233 /*
1234  * Calling this is the point of no return. None of the failures will be
1235  * seen by userspace since either the process is already taking a fatal
1236  * signal (via de_thread() or coredump), or will have SEGV raised
1237  * (after exec_mmap()) by search_binary_handler (see below).
1238  */
1239 int begin_new_exec(struct linux_binprm * bprm)
1240 {
1241         struct task_struct *me = current;
1242         int retval;
1243 
1244         /* Once we are committed compute the creds */
1245         retval = bprm_creds_from_file(bprm);
1246         if (retval)
1247                 return retval;
1248 
1249         /*
1250          * Ensure all future errors are fatal.
1251          */
1252         bprm->point_of_no_return = true;
1253 
1254         /*
1255          * Make this the only thread in the thread group.
1256          */
1257         retval = de_thread(me);
1258         if (retval)
1259                 goto out;
1260 
1261         /*
1262          * Cancel any io_uring activity across execve
1263          */
1264         io_uring_task_cancel();
1265 
1266         /* Ensure the files table is not shared. */
1267         retval = unshare_files();
1268         if (retval)
1269                 goto out;
1270 
1271         /*
1272          * Must be called _before_ exec_mmap() as bprm->mm is
1273          * not visibile until then. This also enables the update
1274          * to be lockless.
1275          */
1276         set_mm_exe_file(bprm->mm, bprm->file);
1277 
1278         /* If the binary is not readable then enforce mm->dumpable=0 */
1279         would_dump(bprm, bprm->file);
1280         if (bprm->have_execfd)
1281                 would_dump(bprm, bprm->executable);
1282 
1283         /*
1284          * Release all of the old mmap stuff
1285          */
1286         acct_arg_size(bprm, 0);
1287         retval = exec_mmap(bprm->mm);
1288         if (retval)
1289                 goto out;
1290 
1291         bprm->mm = NULL;
1292 
1293 #ifdef CONFIG_POSIX_TIMERS
1294         exit_itimers(me->signal);
1295         flush_itimer_signals();
1296 #endif
1297 
1298         /*
1299          * Make the signal table private.
1300          */
1301         retval = unshare_sighand(me);
1302         if (retval)
1303                 goto out_unlock;
1304 
1305         /*
1306          * Ensure that the uaccess routines can actually operate on userspace
1307          * pointers:
1308          */
1309         force_uaccess_begin();
1310 
1311         me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
1312                                         PF_NOFREEZE | PF_NO_SETAFFINITY);
1313         flush_thread();
1314         me->personality &= ~bprm->per_clear;
1315 
1316         clear_syscall_work_syscall_user_dispatch(me);
1317 
1318         /*
1319          * We have to apply CLOEXEC before we change whether the process is
1320          * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1321          * trying to access the should-be-closed file descriptors of a process
1322          * undergoing exec(2).
1323          */
1324         do_close_on_exec(me->files);
1325 
1326         if (bprm->secureexec) {
1327                 /* Make sure parent cannot signal privileged process. */
1328                 me->pdeath_signal = 0;
1329 
1330                 /*
1331                  * For secureexec, reset the stack limit to sane default to
1332                  * avoid bad behavior from the prior rlimits. This has to
1333                  * happen before arch_pick_mmap_layout(), which examines
1334                  * RLIMIT_STACK, but after the point of no return to avoid
1335                  * needing to clean up the change on failure.
1336                  */
1337                 if (bprm->rlim_stack.rlim_cur > _STK_LIM)
1338                         bprm->rlim_stack.rlim_cur = _STK_LIM;
1339         }
1340 
1341         me->sas_ss_sp = me->sas_ss_size = 0;
1342 
1343         /*
1344          * Figure out dumpability. Note that this checking only of current
1345          * is wrong, but userspace depends on it. This should be testing
1346          * bprm->secureexec instead.
1347          */
1348         if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
1349             !(uid_eq(current_euid(), current_uid()) &&
1350               gid_eq(current_egid(), current_gid())))
1351                 set_dumpable(current->mm, suid_dumpable);
1352         else
1353                 set_dumpable(current->mm, SUID_DUMP_USER);
1354 
1355         perf_event_exec();
1356         __set_task_comm(me, kbasename(bprm->filename), true);
1357 
1358         /* An exec changes our domain. We are no longer part of the thread
1359            group */
1360         WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1);
1361         flush_signal_handlers(me, 0);
1362 
1363         retval = set_cred_ucounts(bprm->cred);
1364         if (retval < 0)
1365                 goto out_unlock;
1366 
1367         /*
1368          * install the new credentials for this executable
1369          */
1370         security_bprm_committing_creds(bprm);
1371 
1372         commit_creds(bprm->cred);
1373         bprm->cred = NULL;
1374 
1375         /*
1376          * Disable monitoring for regular users
1377          * when executing setuid binaries. Must
1378          * wait until new credentials are committed
1379          * by commit_creds() above
1380          */
1381         if (get_dumpable(me->mm) != SUID_DUMP_USER)
1382                 perf_event_exit_task(me);
1383         /*
1384          * cred_guard_mutex must be held at least to this point to prevent
1385          * ptrace_attach() from altering our determination of the task's
1386          * credentials; any time after this it may be unlocked.
1387          */
1388         security_bprm_committed_creds(bprm);
1389 
1390         /* Pass the opened binary to the interpreter. */
1391         if (bprm->have_execfd) {
1392                 retval = get_unused_fd_flags(0);
1393                 if (retval < 0)
1394                         goto out_unlock;
1395                 fd_install(retval, bprm->executable);
1396                 bprm->executable = NULL;
1397                 bprm->execfd = retval;
1398         }
1399         return 0;
1400 
1401 out_unlock:
1402         up_write(&me->signal->exec_update_lock);
1403 out:
1404         return retval;
1405 }
1406 EXPORT_SYMBOL(begin_new_exec);
1407 
1408 void would_dump(struct linux_binprm *bprm, struct file *file)
1409 {
1410         struct inode *inode = file_inode(file);
1411         struct user_namespace *mnt_userns = file_mnt_user_ns(file);
1412         if (inode_permission(mnt_userns, inode, MAY_READ) < 0) {
1413                 struct user_namespace *old, *user_ns;
1414                 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1415 
1416                 /* Ensure mm->user_ns contains the executable */
1417                 user_ns = old = bprm->mm->user_ns;
1418                 while ((user_ns != &init_user_ns) &&
1419                        !privileged_wrt_inode_uidgid(user_ns, mnt_userns, inode))
1420                         user_ns = user_ns->parent;
1421 
1422                 if (old != user_ns) {
1423                         bprm->mm->user_ns = get_user_ns(user_ns);
1424                         put_user_ns(old);
1425                 }
1426         }
1427 }
1428 EXPORT_SYMBOL(would_dump);
1429 
1430 void setup_new_exec(struct linux_binprm * bprm)
1431 {
1432         /* Setup things that can depend upon the personality */
1433         struct task_struct *me = current;
1434 
1435         arch_pick_mmap_layout(me->mm, &bprm->rlim_stack);
1436 
1437         arch_setup_new_exec();
1438 
1439         /* Set the new mm task size. We have to do that late because it may
1440          * depend on TIF_32BIT which is only updated in flush_thread() on
1441          * some architectures like powerpc
1442          */
1443         me->mm->task_size = TASK_SIZE;
1444         up_write(&me->signal->exec_update_lock);
1445         mutex_unlock(&me->signal->cred_guard_mutex);
1446 }
1447 EXPORT_SYMBOL(setup_new_exec);
1448 
1449 /* Runs immediately before start_thread() takes over. */
1450 void finalize_exec(struct linux_binprm *bprm)
1451 {
1452         /* Store any stack rlimit changes before starting thread. */
1453         task_lock(current->group_leader);
1454         current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack;
1455         task_unlock(current->group_leader);
1456 }
1457 EXPORT_SYMBOL(finalize_exec);
1458 
1459 /*
1460  * Prepare credentials and lock ->cred_guard_mutex.
1461  * setup_new_exec() commits the new creds and drops the lock.
1462  * Or, if exec fails before, free_bprm() should release ->cred
1463  * and unlock.
1464  */
1465 static int prepare_bprm_creds(struct linux_binprm *bprm)
1466 {
1467         if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1468                 return -ERESTARTNOINTR;
1469 
1470         bprm->cred = prepare_exec_creds();
1471         if (likely(bprm->cred))
1472                 return 0;
1473 
1474         mutex_unlock(&current->signal->cred_guard_mutex);
1475         return -ENOMEM;
1476 }
1477 
1478 static void free_bprm(struct linux_binprm *bprm)
1479 {
1480         if (bprm->mm) {
1481                 acct_arg_size(bprm, 0);
1482                 mmput(bprm->mm);
1483         }
1484         free_arg_pages(bprm);
1485         if (bprm->cred) {
1486                 mutex_unlock(&current->signal->cred_guard_mutex);
1487                 abort_creds(bprm->cred);
1488         }
1489         if (bprm->file) {
1490                 allow_write_access(bprm->file);
1491                 fput(bprm->file);
1492         }
1493         if (bprm->executable)
1494                 fput(bprm->executable);
1495         /* If a binfmt changed the interp, free it. */
1496         if (bprm->interp != bprm->filename)
1497                 kfree(bprm->interp);
1498         kfree(bprm->fdpath);
1499         kfree(bprm);
1500 }
1501 
1502 static struct linux_binprm *alloc_bprm(int fd, struct filename *filename)
1503 {
1504         struct linux_binprm *bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1505         int retval = -ENOMEM;
1506         if (!bprm)
1507                 goto out;
1508 
1509         if (fd == AT_FDCWD || filename->name[0] == '/') {
1510                 bprm->filename = filename->name;
1511         } else {
1512                 if (filename->name[0] == '\0')
1513                         bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd);
1514                 else
1515                         bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s",
1516                                                   fd, filename->name);
1517                 if (!bprm->fdpath)
1518                         goto out_free;
1519 
1520                 bprm->filename = bprm->fdpath;
1521         }
1522         bprm->interp = bprm->filename;
1523 
1524         retval = bprm_mm_init(bprm);
1525         if (retval)
1526                 goto out_free;
1527         return bprm;
1528 
1529 out_free:
1530         free_bprm(bprm);
1531 out:
1532         return ERR_PTR(retval);
1533 }
1534 
1535 int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
1536 {
1537         /* If a binfmt changed the interp, free it first. */
1538         if (bprm->interp != bprm->filename)
1539                 kfree(bprm->interp);
1540         bprm->interp = kstrdup(interp, GFP_KERNEL);
1541         if (!bprm->interp)
1542                 return -ENOMEM;
1543         return 0;
1544 }
1545 EXPORT_SYMBOL(bprm_change_interp);
1546 
1547 /*
1548  * determine how safe it is to execute the proposed program
1549  * - the caller must hold ->cred_guard_mutex to protect against
1550  *   PTRACE_ATTACH or seccomp thread-sync
1551  */
1552 static void check_unsafe_exec(struct linux_binprm *bprm)
1553 {
1554         struct task_struct *p = current, *t;
1555         unsigned n_fs;
1556 
1557         if (p->ptrace)
1558                 bprm->unsafe |= LSM_UNSAFE_PTRACE;
1559 
1560         /*
1561          * This isn't strictly necessary, but it makes it harder for LSMs to
1562          * mess up.
1563          */
1564         if (task_no_new_privs(current))
1565                 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1566 
1567         t = p;
1568         n_fs = 1;
1569         spin_lock(&p->fs->lock);
1570         rcu_read_lock();
1571         while_each_thread(p, t) {
1572                 if (t->fs == p->fs)
1573                         n_fs++;
1574         }
1575         rcu_read_unlock();
1576 
1577         if (p->fs->users > n_fs)
1578                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1579         else
1580                 p->fs->in_exec = 1;
1581         spin_unlock(&p->fs->lock);
1582 }
1583 
1584 static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
1585 {
1586         /* Handle suid and sgid on files */
1587         struct user_namespace *mnt_userns;
1588         struct inode *inode;
1589         unsigned int mode;
1590         kuid_t uid;
1591         kgid_t gid;
1592 
1593         if (!mnt_may_suid(file->f_path.mnt))
1594                 return;
1595 
1596         if (task_no_new_privs(current))
1597                 return;
1598 
1599         inode = file->f_path.dentry->d_inode;
1600         mode = READ_ONCE(inode->i_mode);
1601         if (!(mode & (S_ISUID|S_ISGID)))
1602                 return;
1603 
1604         mnt_userns = file_mnt_user_ns(file);
1605 
1606         /* Be careful if suid/sgid is set */
1607         inode_lock(inode);
1608 
1609         /* reload atomically mode/uid/gid now that lock held */
1610         mode = inode->i_mode;
1611         uid = i_uid_into_mnt(mnt_userns, inode);
1612         gid = i_gid_into_mnt(mnt_userns, inode);
1613         inode_unlock(inode);
1614 
1615         /* We ignore suid/sgid if there are no mappings for them in the ns */
1616         if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
1617                  !kgid_has_mapping(bprm->cred->user_ns, gid))
1618                 return;
1619 
1620         if (mode & S_ISUID) {
1621                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1622                 bprm->cred->euid = uid;
1623         }
1624 
1625         if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1626                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1627                 bprm->cred->egid = gid;
1628         }
1629 }
1630 
1631 /*
1632  * Compute brpm->cred based upon the final binary.
1633  */
1634 static int bprm_creds_from_file(struct linux_binprm *bprm)
1635 {
1636         /* Compute creds based on which file? */
1637         struct file *file = bprm->execfd_creds ? bprm->executable : bprm->file;
1638 
1639         bprm_fill_uid(bprm, file);
1640         return security_bprm_creds_from_file(bprm, file);
1641 }
1642 
1643 /*
1644  * Fill the binprm structure from the inode.
1645  * Read the first BINPRM_BUF_SIZE bytes
1646  *
1647  * This may be called multiple times for binary chains (scripts for example).
1648  */
1649 static int prepare_binprm(struct linux_binprm *bprm)
1650 {
1651         loff_t pos = 0;
1652 
1653         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1654         return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
1655 }
1656 
1657 /*
1658  * Arguments are '\0' separated strings found at the location bprm->p
1659  * points to; chop off the first by relocating brpm->p to right after
1660  * the first '\0' encountered.
1661  */
1662 int remove_arg_zero(struct linux_binprm *bprm)
1663 {
1664         int ret = 0;
1665         unsigned long offset;
1666         char *kaddr;
1667         struct page *page;
1668 
1669         if (!bprm->argc)
1670                 return 0;
1671 
1672         do {
1673                 offset = bprm->p & ~PAGE_MASK;
1674                 page = get_arg_page(bprm, bprm->p, 0);
1675                 if (!page) {
1676                         ret = -EFAULT;
1677                         goto out;
1678                 }
1679                 kaddr = kmap_atomic(page);
1680 
1681                 for (; offset < PAGE_SIZE && kaddr[offset];
1682                                 offset++, bprm->p++)
1683                         ;
1684 
1685                 kunmap_atomic(kaddr);
1686                 put_arg_page(page);
1687         } while (offset == PAGE_SIZE);
1688 
1689         bprm->p++;
1690         bprm->argc--;
1691         ret = 0;
1692 
1693 out:
1694         return ret;
1695 }
1696 EXPORT_SYMBOL(remove_arg_zero);
1697 
1698 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1699 /*
1700  * cycle the list of binary formats handler, until one recognizes the image
1701  */
1702 static int search_binary_handler(struct linux_binprm *bprm)
1703 {
1704         bool need_retry = IS_ENABLED(CONFIG_MODULES);
1705         struct linux_binfmt *fmt;
1706         int retval;
1707 
1708         retval = prepare_binprm(bprm);
1709         if (retval < 0)
1710                 return retval;
1711 
1712         retval = security_bprm_check(bprm);
1713         if (retval)
1714                 return retval;
1715 
1716         retval = -ENOENT;
1717  retry:
1718         read_lock(&binfmt_lock);
1719         list_for_each_entry(fmt, &formats, lh) {
1720                 if (!try_module_get(fmt->module))
1721                         continue;
1722                 read_unlock(&binfmt_lock);
1723 
1724                 retval = fmt->load_binary(bprm);
1725 
1726                 read_lock(&binfmt_lock);
1727                 put_binfmt(fmt);
1728                 if (bprm->point_of_no_return || (retval != -ENOEXEC)) {
1729                         read_unlock(&binfmt_lock);
1730                         return retval;
1731                 }
1732         }
1733         read_unlock(&binfmt_lock);
1734 
1735         if (need_retry) {
1736                 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1737                     printable(bprm->buf[2]) && printable(bprm->buf[3]))
1738                         return retval;
1739                 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1740                         return retval;
1741                 need_retry = false;
1742                 goto retry;
1743         }
1744 
1745         return retval;
1746 }
1747 
1748 static int exec_binprm(struct linux_binprm *bprm)
1749 {
1750         pid_t old_pid, old_vpid;
1751         int ret, depth;
1752 
1753         /* Need to fetch pid before load_binary changes it */
1754         old_pid = current->pid;
1755         rcu_read_lock();
1756         old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1757         rcu_read_unlock();
1758 
1759         /* This allows 4 levels of binfmt rewrites before failing hard. */
1760         for (depth = 0;; depth++) {
1761                 struct file *exec;
1762                 if (depth > 5)
1763                         return -ELOOP;
1764 
1765                 ret = search_binary_handler(bprm);
1766                 if (ret < 0)
1767                         return ret;
1768                 if (!bprm->interpreter)
1769                         break;
1770 
1771                 exec = bprm->file;
1772                 bprm->file = bprm->interpreter;
1773                 bprm->interpreter = NULL;
1774 
1775                 allow_write_access(exec);
1776                 if (unlikely(bprm->have_execfd)) {
1777                         if (bprm->executable) {
1778                                 fput(exec);
1779                                 return -ENOEXEC;
1780                         }
1781                         bprm->executable = exec;
1782                 } else
1783                         fput(exec);
1784         }
1785 
1786         audit_bprm(bprm);
1787         trace_sched_process_exec(current, old_pid, bprm);
1788         ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1789         proc_exec_connector(current);
1790         return 0;
1791 }
1792 
1793 /*
1794  * sys_execve() executes a new program.
1795  */
1796 static int bprm_execve(struct linux_binprm *bprm,
1797                        int fd, struct filename *filename, int flags)
1798 {
1799         struct file *file;
1800         int retval;
1801 
1802         retval = prepare_bprm_creds(bprm);
1803         if (retval)
1804                 return retval;
1805 
1806         check_unsafe_exec(bprm);
1807         current->in_execve = 1;
1808 
1809         file = do_open_execat(fd, filename, flags);
1810         retval = PTR_ERR(file);
1811         if (IS_ERR(file))
1812                 goto out_unmark;
1813 
1814         sched_exec();
1815 
1816         bprm->file = file;
1817         /*
1818          * Record that a name derived from an O_CLOEXEC fd will be
1819          * inaccessible after exec.  This allows the code in exec to
1820          * choose to fail when the executable is not mmaped into the
1821          * interpreter and an open file descriptor is not passed to
1822          * the interpreter.  This makes for a better user experience
1823          * than having the interpreter start and then immediately fail
1824          * when it finds the executable is inaccessible.
1825          */
1826         if (bprm->fdpath && get_close_on_exec(fd))
1827                 bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1828 
1829         /* Set the unchanging part of bprm->cred */
1830         retval = security_bprm_creds_for_exec(bprm);
1831         if (retval)
1832                 goto out;
1833 
1834         retval = ccs_exec_binprm(bprm);
1835         if (retval < 0)
1836                 goto out;
1837 
1838         /* execve succeeded */
1839         current->fs->in_exec = 0;
1840         current->in_execve = 0;
1841         rseq_execve(current);
1842         acct_update_integrals(current);
1843         task_numa_free(current, false);
1844         return retval;
1845 
1846 out:
1847         /*
1848          * If past the point of no return ensure the code never
1849          * returns to the userspace process.  Use an existing fatal
1850          * signal if present otherwise terminate the process with
1851          * SIGSEGV.
1852          */
1853         if (bprm->point_of_no_return && !fatal_signal_pending(current))
1854                 force_sigsegv(SIGSEGV);
1855 
1856 out_unmark:
1857         current->fs->in_exec = 0;
1858         current->in_execve = 0;
1859 
1860         return retval;
1861 }
1862 
1863 static int do_execveat_common(int fd, struct filename *filename,
1864                               struct user_arg_ptr argv,
1865                               struct user_arg_ptr envp,
1866                               int flags)
1867 {
1868         struct linux_binprm *bprm;
1869         int retval;
1870 
1871         if (IS_ERR(filename))
1872                 return PTR_ERR(filename);
1873 
1874         /*
1875          * We move the actual failure in case of RLIMIT_NPROC excess from
1876          * set*uid() to execve() because too many poorly written programs
1877          * don't check setuid() return code.  Here we additionally recheck
1878          * whether NPROC limit is still exceeded.
1879          */
1880         if ((current->flags & PF_NPROC_EXCEEDED) &&
1881             atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
1882                 retval = -EAGAIN;
1883                 goto out_ret;
1884         }
1885 
1886         /* We're below the limit (still or again), so we don't want to make
1887          * further execve() calls fail. */
1888         current->flags &= ~PF_NPROC_EXCEEDED;
1889 
1890         bprm = alloc_bprm(fd, filename);
1891         if (IS_ERR(bprm)) {
1892                 retval = PTR_ERR(bprm);
1893                 goto out_ret;
1894         }
1895 
1896         retval = count(argv, MAX_ARG_STRINGS);
1897         if (retval < 0)
1898                 goto out_free;
1899         bprm->argc = retval;
1900 
1901         retval = count(envp, MAX_ARG_STRINGS);
1902         if (retval < 0)
1903                 goto out_free;
1904         bprm->envc = retval;
1905 
1906         retval = bprm_stack_limits(bprm);
1907         if (retval < 0)
1908                 goto out_free;
1909 
1910         retval = copy_string_kernel(bprm->filename, bprm);
1911         if (retval < 0)
1912                 goto out_free;
1913         bprm->exec = bprm->p;
1914 
1915         retval = copy_strings(bprm->envc, envp, bprm);
1916         if (retval < 0)
1917                 goto out_free;
1918 
1919         retval = copy_strings(bprm->argc, argv, bprm);
1920         if (retval < 0)
1921                 goto out_free;
1922 
1923         retval = bprm_execve(bprm, fd, filename, flags);
1924 out_free:
1925         free_bprm(bprm);
1926 
1927 out_ret:
1928         putname(filename);
1929         return retval;
1930 }
1931 
1932 int kernel_execve(const char *kernel_filename,
1933                   const char *const *argv, const char *const *envp)
1934 {
1935         struct filename *filename;
1936         struct linux_binprm *bprm;
1937         int fd = AT_FDCWD;
1938         int retval;
1939 
1940         filename = getname_kernel(kernel_filename);
1941         if (IS_ERR(filename))
1942                 return PTR_ERR(filename);
1943 
1944         bprm = alloc_bprm(fd, filename);
1945         if (IS_ERR(bprm)) {
1946                 retval = PTR_ERR(bprm);
1947                 goto out_ret;
1948         }
1949 
1950         retval = count_strings_kernel(argv);
1951         if (retval < 0)
1952                 goto out_free;
1953         bprm->argc = retval;
1954 
1955         retval = count_strings_kernel(envp);
1956         if (retval < 0)
1957                 goto out_free;
1958         bprm->envc = retval;
1959 
1960         retval = bprm_stack_limits(bprm);
1961         if (retval < 0)
1962                 goto out_free;
1963 
1964         retval = copy_string_kernel(bprm->filename, bprm);
1965         if (retval < 0)
1966                 goto out_free;
1967         bprm->exec = bprm->p;
1968 
1969         retval = copy_strings_kernel(bprm->envc, envp, bprm);
1970         if (retval < 0)
1971                 goto out_free;
1972 
1973         retval = copy_strings_kernel(bprm->argc, argv, bprm);
1974         if (retval < 0)
1975                 goto out_free;
1976 
1977         retval = bprm_execve(bprm, fd, filename, 0);
1978 out_free:
1979         free_bprm(bprm);
1980 out_ret:
1981         putname(filename);
1982         return retval;
1983 }
1984 
1985 static int do_execve(struct filename *filename,
1986         const char __user *const __user *__argv,
1987         const char __user *const __user *__envp)
1988 {
1989         struct user_arg_ptr argv = { .ptr.native = __argv };
1990         struct user_arg_ptr envp = { .ptr.native = __envp };
1991         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1992 }
1993 
1994 static int do_execveat(int fd, struct filename *filename,
1995                 const char __user *const __user *__argv,
1996                 const char __user *const __user *__envp,
1997                 int flags)
1998 {
1999         struct user_arg_ptr argv = { .ptr.native = __argv };
2000         struct user_arg_ptr envp = { .ptr.native = __envp };
2001 
2002         return do_execveat_common(fd, filename, argv, envp, flags);
2003 }
2004 
2005 #ifdef CONFIG_COMPAT
2006 static int compat_do_execve(struct filename *filename,
2007         const compat_uptr_t __user *__argv,
2008         const compat_uptr_t __user *__envp)
2009 {
2010         struct user_arg_ptr argv = {
2011                 .is_compat = true,
2012                 .ptr.compat = __argv,
2013         };
2014         struct user_arg_ptr envp = {
2015                 .is_compat = true,
2016                 .ptr.compat = __envp,
2017         };
2018         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
2019 }
2020 
2021 static int compat_do_execveat(int fd, struct filename *filename,
2022                               const compat_uptr_t __user *__argv,
2023                               const compat_uptr_t __user *__envp,
2024                               int flags)
2025 {
2026         struct user_arg_ptr argv = {
2027                 .is_compat = true,
2028                 .ptr.compat = __argv,
2029         };
2030         struct user_arg_ptr envp = {
2031                 .is_compat = true,
2032                 .ptr.compat = __envp,
2033         };
2034         return do_execveat_common(fd, filename, argv, envp, flags);
2035 }
2036 #endif
2037 
2038 void set_binfmt(struct linux_binfmt *new)
2039 {
2040         struct mm_struct *mm = current->mm;
2041 
2042         if (mm->binfmt)
2043                 module_put(mm->binfmt->module);
2044 
2045         mm->binfmt = new;
2046         if (new)
2047                 __module_get(new->module);
2048 }
2049 EXPORT_SYMBOL(set_binfmt);
2050 
2051 /*
2052  * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
2053  */
2054 void set_dumpable(struct mm_struct *mm, int value)
2055 {
2056         if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
2057                 return;
2058 
2059         set_mask_bits(&mm->flags, MMF_DUMPABLE_MASK, value);
2060 }
2061 
2062 SYSCALL_DEFINE3(execve,
2063                 const char __user *, filename,
2064                 const char __user *const __user *, argv,
2065                 const char __user *const __user *, envp)
2066 {
2067         return do_execve(getname(filename), argv, envp);
2068 }
2069 
2070 SYSCALL_DEFINE5(execveat,
2071                 int, fd, const char __user *, filename,
2072                 const char __user *const __user *, argv,
2073                 const char __user *const __user *, envp,
2074                 int, flags)
2075 {
2076         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
2077 
2078         return do_execveat(fd,
2079                            getname_flags(filename, lookup_flags, NULL),
2080                            argv, envp, flags);
2081 }
2082 
2083 #ifdef CONFIG_COMPAT
2084 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
2085         const compat_uptr_t __user *, argv,
2086         const compat_uptr_t __user *, envp)
2087 {
2088         return compat_do_execve(getname(filename), argv, envp);
2089 }
2090 
2091 COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
2092                        const char __user *, filename,
2093                        const compat_uptr_t __user *, argv,
2094                        const compat_uptr_t __user *, envp,
2095                        int,  flags)
2096 {
2097         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
2098 
2099         return compat_do_execveat(fd,
2100                                   getname_flags(filename, lookup_flags, NULL),
2101                                   argv, envp, flags);
2102 }
2103 #endif
2104 

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