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TOMOYO Linux Cross Reference
Linux/fs/exec.c

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

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