projects/linux·blob v7.2 · refs

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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/stat.h>
32#include <linux/fcntl.h>
33#include <linux/swap.h>
34#include <linux/string.h>
35#include <linux/init.h>
36#include <linux/sched/mm.h>
37#include <linux/sched/coredump.h>
38#include <linux/sched/exec_state.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/kmod.h>
60#include <linux/fsnotify.h>
61#include <linux/fs_struct.h>
62#include <linux/oom.h>
63#include <linux/compat.h>
64#include <linux/vmalloc.h>
65#include <linux/io_uring.h>
66#include <linux/syscall_user_dispatch.h>
67#include <linux/coredump.h>
68#include <linux/time_namespace.h>
69#include <linux/user_events.h>
70#include <linux/rseq.h>
71#include <linux/ksm.h>
72
73#include <linux/uaccess.h>
74#include <asm/mmu_context.h>
75#include <asm/tlb.h>
76
77#include <trace/events/task.h>
78#include "internal.h"
79
80#include <trace/events/sched.h>
81
82/* For vma exec functions. */
83#include "../mm/internal.h"
84
85static int bprm_creds_from_file(struct linux_binprm *bprm);
86
87int suid_dumpable = 0;
88
89static LIST_HEAD(formats);
90static DEFINE_RWLOCK(binfmt_lock);
91
92void __register_binfmt(struct linux_binfmt * fmt, int insert)
93{
94 write_lock(&binfmt_lock);
95 insert ? list_add(&fmt->lh, &formats) :
96 list_add_tail(&fmt->lh, &formats);
97 write_unlock(&binfmt_lock);
98}
99
100EXPORT_SYMBOL(__register_binfmt);
101
102void unregister_binfmt(struct linux_binfmt * fmt)
103{
104 write_lock(&binfmt_lock);
105 list_del(&fmt->lh);
106 write_unlock(&binfmt_lock);
107}
108
109EXPORT_SYMBOL(unregister_binfmt);
110
111static inline void put_binfmt(struct linux_binfmt * fmt)
112{
113 module_put(fmt->module);
114}
115
116bool path_noexec(const struct path *path)
117{
118 /* If it's an anonymous inode make sure that we catch any shenanigans. */
119 VFS_WARN_ON_ONCE(IS_ANON_FILE(d_inode(path->dentry)) &&
120 !(path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC));
121 return (path->mnt->mnt_flags & MNT_NOEXEC) ||
122 (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
123}
124
125#ifdef CONFIG_MMU
126/*
127 * The nascent bprm->mm is not visible until exec_mmap() but it can
128 * use a lot of memory, account these pages in current->mm temporary
129 * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
130 * change the counter back via acct_arg_size(0).
131 */
132static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
133{
134 struct mm_struct *mm = current->mm;
135 long diff = (long)(pages - bprm->vma_pages);
136
137 if (!mm || !diff)
138 return;
139
140 bprm->vma_pages = pages;
141 add_mm_counter(mm, MM_ANONPAGES, diff);
142}
143
144static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
145 int write)
146{
147 struct page *page;
148 struct vm_area_struct *vma = bprm->vma;
149 struct mm_struct *mm = bprm->mm;
150 int ret;
151
152 /*
153 * Avoid relying on expanding the stack down in GUP (which
154 * does not work for STACK_GROWSUP anyway), and just do it
155 * ahead of time.
156 */
157 if (!mmap_read_lock_maybe_expand(mm, vma, pos, write))
158 return NULL;
159
160 /*
161 * We are doing an exec(). 'current' is the process
162 * doing the exec and 'mm' is the new process's mm.
163 */
164 ret = get_user_pages_remote(mm, pos, 1,
165 write ? FOLL_WRITE : 0,
166 &page, NULL);
167 mmap_read_unlock(mm);
168 if (ret <= 0)
169 return NULL;
170
171 if (write)
172 acct_arg_size(bprm, vma_pages(vma));
173
174 return page;
175}
176
177static void put_arg_page(struct page *page)
178{
179 put_page(page);
180}
181
182static void free_arg_pages(struct linux_binprm *bprm)
183{
184}
185
186static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
187 struct page *page)
188{
189 flush_cache_page(bprm->vma, pos, page_to_pfn(page));
190}
191
192static bool valid_arg_len(struct linux_binprm *bprm, long len)
193{
194 return len <= MAX_ARG_STRLEN;
195}
196
197#else
198
199static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
200{
201}
202
203static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
204 int write)
205{
206 struct page *page;
207
208 page = bprm->page[pos / PAGE_SIZE];
209 if (!page && write) {
210 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
211 if (!page)
212 return NULL;
213 bprm->page[pos / PAGE_SIZE] = page;
214 }
215
216 return page;
217}
218
219static void put_arg_page(struct page *page)
220{
221}
222
223static void free_arg_page(struct linux_binprm *bprm, int i)
224{
225 if (bprm->page[i]) {
226 __free_page(bprm->page[i]);
227 bprm->page[i] = NULL;
228 }
229}
230
231static void free_arg_pages(struct linux_binprm *bprm)
232{
233 int i;
234
235 for (i = 0; i < MAX_ARG_PAGES; i++)
236 free_arg_page(bprm, i);
237}
238
239static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
240 struct page *page)
241{
242}
243
244static bool valid_arg_len(struct linux_binprm *bprm, long len)
245{
246 return len <= bprm->p;
247}
248
249#endif /* CONFIG_MMU */
250
251/*
252 * Create a new mm_struct and populate it with a temporary stack
253 * vm_area_struct. We don't have enough context at this point to set the stack
254 * flags, permissions, and offset, so we use temporary values. We'll update
255 * them later in setup_arg_pages().
256 */
257static int bprm_mm_init(struct linux_binprm *bprm)
258{
259 int err;
260 struct mm_struct *mm = NULL;
261
262 bprm->mm = mm = mm_alloc();
263 err = -ENOMEM;
264 if (!mm)
265 goto err;
266
267 /* Staged for would_dump() narrowing; consumed by begin_new_exec(). */
268 bprm->user_ns = get_user_ns(current_user_ns());
269
270 /* Save current stack limit for all calculations made during exec. */
271 task_lock(current->group_leader);
272 bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK];
273 task_unlock(current->group_leader);
274
275#ifndef CONFIG_MMU
276 bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
277#else
278 err = create_init_stack_vma(bprm->mm, &bprm->vma, &bprm->p);
279 if (err)
280 goto err;
281#endif
282
283 return 0;
284
285err:
286 if (mm) {
287 bprm->mm = NULL;
288 mmdrop(mm);
289 }
290
291 return err;
292}
293
294struct user_arg_ptr {
295#ifdef CONFIG_COMPAT
296 bool is_compat;
297#endif
298 union {
299 const char __user *const __user *native;
300#ifdef CONFIG_COMPAT
301 const compat_uptr_t __user *compat;
302#endif
303 } ptr;
304};
305
306static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
307{
308 const char __user *native;
309
310#ifdef CONFIG_COMPAT
311 if (unlikely(argv.is_compat)) {
312 compat_uptr_t compat;
313
314 if (get_user(compat, argv.ptr.compat + nr))
315 return ERR_PTR(-EFAULT);
316
317 return compat_ptr(compat);
318 }
319#endif
320
321 if (get_user(native, argv.ptr.native + nr))
322 return ERR_PTR(-EFAULT);
323
324 return native;
325}
326
327/*
328 * count() counts the number of strings in array ARGV.
329 */
330static int count(struct user_arg_ptr argv, int max)
331{
332 int i = 0;
333
334 if (argv.ptr.native != NULL) {
335 for (;;) {
336 const char __user *p = get_user_arg_ptr(argv, i);
337
338 if (!p)
339 break;
340
341 if (IS_ERR(p))
342 return -EFAULT;
343
344 if (i >= max)
345 return -E2BIG;
346 ++i;
347
348 if (fatal_signal_pending(current))
349 return -ERESTARTNOHAND;
350 cond_resched();
351 }
352 }
353 return i;
354}
355
356static int count_strings_kernel(const char *const *argv)
357{
358 int i;
359
360 if (!argv)
361 return 0;
362
363 for (i = 0; argv[i]; ++i) {
364 if (i >= MAX_ARG_STRINGS)
365 return -E2BIG;
366 if (fatal_signal_pending(current))
367 return -ERESTARTNOHAND;
368 cond_resched();
369 }
370 return i;
371}
372
373static inline int bprm_set_stack_limit(struct linux_binprm *bprm,
374 unsigned long limit)
375{
376#ifdef CONFIG_MMU
377 /* Avoid a pathological bprm->p. */
378 if (bprm->p < limit)
379 return -E2BIG;
380 bprm->argmin = bprm->p - limit;
381#endif
382 return 0;
383}
384static inline bool bprm_hit_stack_limit(struct linux_binprm *bprm)
385{
386#ifdef CONFIG_MMU
387 return bprm->p < bprm->argmin;
388#else
389 return false;
390#endif
391}
392
393/*
394 * Calculate bprm->argmin from:
395 * - _STK_LIM
396 * - ARG_MAX
397 * - bprm->rlim_stack.rlim_cur
398 * - bprm->argc
399 * - bprm->envc
400 * - bprm->p
401 */
402static int bprm_stack_limits(struct linux_binprm *bprm)
403{
404 unsigned long limit, ptr_size;
405
406 /*
407 * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
408 * (whichever is smaller) for the argv+env strings.
409 * This ensures that:
410 * - the remaining binfmt code will not run out of stack space,
411 * - the program will have a reasonable amount of stack left
412 * to work from.
413 */
414 limit = _STK_LIM / 4 * 3;
415 limit = min(limit, bprm->rlim_stack.rlim_cur / 4);
416 /*
417 * We've historically supported up to 32 pages (ARG_MAX)
418 * of argument strings even with small stacks
419 */
420 limit = max_t(unsigned long, limit, ARG_MAX);
421 /* Reject totally pathological counts. */
422 if (bprm->argc < 0 || bprm->envc < 0)
423 return -E2BIG;
424 /*
425 * We must account for the size of all the argv and envp pointers to
426 * the argv and envp strings, since they will also take up space in
427 * the stack. They aren't stored until much later when we can't
428 * signal to the parent that the child has run out of stack space.
429 * Instead, calculate it here so it's possible to fail gracefully.
430 *
431 * In the case of argc = 0, make sure there is space for adding a
432 * empty string (which will bump argc to 1), to ensure confused
433 * userspace programs don't start processing from argv[1], thinking
434 * argc can never be 0, to keep them from walking envp by accident.
435 * See do_execveat_common().
436 */
437 if (check_add_overflow(max(bprm->argc, 1), bprm->envc, &ptr_size) ||
438 check_mul_overflow(ptr_size, sizeof(void *), &ptr_size))
439 return -E2BIG;
440 if (limit <= ptr_size)
441 return -E2BIG;
442 limit -= ptr_size;
443
444 return bprm_set_stack_limit(bprm, limit);
445}
446
447/*
448 * 'copy_strings()' copies argument/environment strings from the old
449 * processes's memory to the new process's stack. The call to get_user_pages()
450 * ensures the destination page is created and not swapped out.
451 */
452static int copy_strings(int argc, struct user_arg_ptr argv,
453 struct linux_binprm *bprm)
454{
455 struct page *kmapped_page = NULL;
456 char *kaddr = NULL;
457 unsigned long kpos = 0;
458 int ret;
459
460 while (argc-- > 0) {
461 const char __user *str;
462 int len;
463 unsigned long pos;
464
465 ret = -EFAULT;
466 str = get_user_arg_ptr(argv, argc);
467 if (IS_ERR(str))
468 goto out;
469
470 len = strnlen_user(str, MAX_ARG_STRLEN);
471 if (!len)
472 goto out;
473
474 ret = -E2BIG;
475 if (!valid_arg_len(bprm, len))
476 goto out;
477
478 /* We're going to work our way backwards. */
479 pos = bprm->p;
480 str += len;
481 bprm->p -= len;
482 if (bprm_hit_stack_limit(bprm))
483 goto out;
484
485 while (len > 0) {
486 int offset, bytes_to_copy;
487
488 if (fatal_signal_pending(current)) {
489 ret = -ERESTARTNOHAND;
490 goto out;
491 }
492 cond_resched();
493
494 offset = pos % PAGE_SIZE;
495 if (offset == 0)
496 offset = PAGE_SIZE;
497
498 bytes_to_copy = offset;
499 if (bytes_to_copy > len)
500 bytes_to_copy = len;
501
502 offset -= bytes_to_copy;
503 pos -= bytes_to_copy;
504 str -= bytes_to_copy;
505 len -= bytes_to_copy;
506
507 if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
508 struct page *page;
509
510 page = get_arg_page(bprm, pos, 1);
511 if (!page) {
512 ret = -E2BIG;
513 goto out;
514 }
515
516 if (kmapped_page) {
517 flush_dcache_page(kmapped_page);
518 kunmap_local(kaddr);
519 put_arg_page(kmapped_page);
520 }
521 kmapped_page = page;
522 kaddr = kmap_local_page(kmapped_page);
523 kpos = pos & PAGE_MASK;
524 flush_arg_page(bprm, kpos, kmapped_page);
525 }
526 if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
527 ret = -EFAULT;
528 goto out;
529 }
530 }
531 }
532 ret = 0;
533out:
534 if (kmapped_page) {
535 flush_dcache_page(kmapped_page);
536 kunmap_local(kaddr);
537 put_arg_page(kmapped_page);
538 }
539 return ret;
540}
541
542/*
543 * Copy and argument/environment string from the kernel to the processes stack.
544 */
545int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
546{
547 int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;
548 unsigned long pos = bprm->p;
549
550 if (len == 0)
551 return -EFAULT;
552 if (!valid_arg_len(bprm, len))
553 return -E2BIG;
554
555 /* We're going to work our way backwards. */
556 arg += len;
557 bprm->p -= len;
558 if (bprm_hit_stack_limit(bprm))
559 return -E2BIG;
560
561 while (len > 0) {
562 unsigned int bytes_to_copy = min(len,
563 min_not_zero(offset_in_page(pos), PAGE_SIZE));
564 struct page *page;
565
566 pos -= bytes_to_copy;
567 arg -= bytes_to_copy;
568 len -= bytes_to_copy;
569
570 page = get_arg_page(bprm, pos, 1);
571 if (!page)
572 return -E2BIG;
573 flush_arg_page(bprm, pos & PAGE_MASK, page);
574 memcpy_to_page(page, offset_in_page(pos), arg, bytes_to_copy);
575 put_arg_page(page);
576 }
577
578 return 0;
579}
580EXPORT_SYMBOL(copy_string_kernel);
581
582static int copy_strings_kernel(int argc, const char *const *argv,
583 struct linux_binprm *bprm)
584{
585 while (argc-- > 0) {
586 int ret = copy_string_kernel(argv[argc], bprm);
587 if (ret < 0)
588 return ret;
589 if (fatal_signal_pending(current))
590 return -ERESTARTNOHAND;
591 cond_resched();
592 }
593 return 0;
594}
595
596#ifdef CONFIG_MMU
597
598/*
599 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
600 * the stack is optionally relocated, and some extra space is added.
601 */
602int setup_arg_pages(struct linux_binprm *bprm,
603 unsigned long stack_top,
604 int executable_stack)
605{
606 int ret;
607 unsigned long stack_shift;
608 struct mm_struct *mm = current->mm;
609 struct vm_area_struct *vma = bprm->vma;
610 struct vm_area_struct *prev = NULL;
611 vm_flags_t vm_flags;
612 unsigned long stack_base;
613 unsigned long stack_size;
614 unsigned long stack_expand;
615 unsigned long rlim_stack;
616 struct mmu_gather tlb;
617 struct vma_iterator vmi;
618
619#ifdef CONFIG_STACK_GROWSUP
620 /* Limit stack size */
621 stack_base = bprm->rlim_stack.rlim_max;
622
623 stack_base = calc_max_stack_size(stack_base);
624
625 /* Add space for stack randomization. */
626 if (current->flags & PF_RANDOMIZE)
627 stack_base += (STACK_RND_MASK << PAGE_SHIFT);
628
629 /* Make sure we didn't let the argument array grow too large. */
630 if (vma->vm_end - vma->vm_start > stack_base)
631 return -ENOMEM;
632
633 stack_base = PAGE_ALIGN(stack_top - stack_base);
634
635 stack_shift = vma->vm_start - stack_base;
636 mm->arg_start = bprm->p - stack_shift;
637 bprm->p = vma->vm_end - stack_shift;
638#else
639 stack_top = arch_align_stack(stack_top);
640 stack_top = PAGE_ALIGN(stack_top);
641
642 if (unlikely(stack_top < mmap_min_addr) ||
643 unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
644 return -ENOMEM;
645
646 stack_shift = vma->vm_end - stack_top;
647
648 bprm->p -= stack_shift;
649 mm->arg_start = bprm->p;
650#endif
651
652 bprm->exec -= stack_shift;
653
654 if (mmap_write_lock_killable(mm))
655 return -EINTR;
656
657 vm_flags = VM_STACK_FLAGS;
658
659 /*
660 * Adjust stack execute permissions; explicitly enable for
661 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
662 * (arch default) otherwise.
663 */
664 if (unlikely(executable_stack == EXSTACK_ENABLE_X))
665 vm_flags |= VM_EXEC;
666 else if (executable_stack == EXSTACK_DISABLE_X)
667 vm_flags &= ~VM_EXEC;
668 vm_flags |= mm->def_flags;
669 vm_flags |= VM_STACK_INCOMPLETE_SETUP;
670
671 vma_iter_init(&vmi, mm, vma->vm_start);
672
673 tlb_gather_mmu(&tlb, mm);
674 ret = mprotect_fixup(&vmi, &tlb, vma, &prev, vma->vm_start, vma->vm_end,
675 vm_flags);
676 tlb_finish_mmu(&tlb);
677
678 if (ret)
679 goto out_unlock;
680 BUG_ON(prev != vma);
681
682 if (unlikely(vm_flags & VM_EXEC)) {
683 pr_warn_once("process '%pD4' started with executable stack\n",
684 bprm->file);
685 }
686
687 /* Move stack pages down in memory. */
688 if (stack_shift) {
689 /*
690 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once
691 * the binfmt code determines where the new stack should reside, we shift it to
692 * its final location.
693 */
694 ret = relocate_vma_down(vma, stack_shift);
695 if (ret)
696 goto out_unlock;
697 }
698
699 /* mprotect_fixup is overkill to remove the temporary stack flags */
700 vm_flags_clear(vma, VM_STACK_INCOMPLETE_SETUP);
701
702 stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
703 stack_size = vma->vm_end - vma->vm_start;
704 /*
705 * Align this down to a page boundary as expand_stack
706 * will align it up.
707 */
708 rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK;
709
710 stack_expand = min(rlim_stack, stack_size + stack_expand);
711
712#ifdef CONFIG_STACK_GROWSUP
713 stack_base = vma->vm_start + stack_expand;
714#else
715 stack_base = vma->vm_end - stack_expand;
716#endif
717 current->mm->start_stack = bprm->p;
718 ret = expand_stack_locked(vma, stack_base);
719 if (ret)
720 ret = -EFAULT;
721
722out_unlock:
723 mmap_write_unlock(mm);
724 return ret;
725}
726EXPORT_SYMBOL(setup_arg_pages);
727
728#else
729
730/*
731 * Transfer the program arguments and environment from the holding pages
732 * onto the stack. The provided stack pointer is adjusted accordingly.
733 */
734int transfer_args_to_stack(struct linux_binprm *bprm,
735 unsigned long *sp_location)
736{
737 unsigned long index, stop, sp;
738 int ret = 0;
739
740 stop = bprm->p >> PAGE_SHIFT;
741 sp = *sp_location;
742
743 for (index = MAX_ARG_PAGES; index-- > stop; ) {
744 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
745 char *src = kmap_local_page(bprm->page[index]) + offset;
746 sp -= PAGE_SIZE - offset;
747 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
748 ret = -EFAULT;
749 kunmap_local(src);
750 if (ret)
751 goto out;
752 }
753
754 bprm->exec += *sp_location - MAX_ARG_PAGES * PAGE_SIZE;
755 *sp_location = sp;
756
757out:
758 return ret;
759}
760EXPORT_SYMBOL(transfer_args_to_stack);
761
762#endif /* CONFIG_MMU */
763
764/*
765 * On success, caller must call do_close_execat() on the returned
766 * struct file to close it.
767 */
768static struct file *do_open_execat(int fd, struct filename *name, int flags)
769{
770 int err;
771 struct file *file __free(fput) = NULL;
772 struct open_flags open_exec_flags = {
773 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
774 .acc_mode = MAY_EXEC,
775 .intent = LOOKUP_OPEN,
776 .lookup_flags = LOOKUP_FOLLOW,
777 };
778
779 if ((flags &
780 ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH | AT_EXECVE_CHECK)) != 0)
781 return ERR_PTR(-EINVAL);
782 if (flags & AT_SYMLINK_NOFOLLOW)
783 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
784
785 file = do_file_open(fd, name, &open_exec_flags);
786 if (IS_ERR(file))
787 return file;
788
789 if (path_noexec(&file->f_path))
790 return ERR_PTR(-EACCES);
791
792 /*
793 * In the past the regular type check was here. It moved to may_open() in
794 * 633fb6ac3980 ("exec: move S_ISREG() check earlier"). Since then it is
795 * an invariant that all non-regular files error out before we get here.
796 */
797 if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode)))
798 return ERR_PTR(-EACCES);
799
800 err = exe_file_deny_write_access(file);
801 if (err)
802 return ERR_PTR(err);
803
804 return no_free_ptr(file);
805}
806
807/**
808 * open_exec - Open a path name for execution
809 *
810 * @name: path name to open with the intent of executing it.
811 *
812 * Returns ERR_PTR on failure or allocated struct file on success.
813 *
814 * As this is a wrapper for the internal do_open_execat(), callers
815 * must call exe_file_allow_write_access() before fput() on release. Also see
816 * do_close_execat().
817 */
818struct file *open_exec(const char *name)
819{
820 CLASS(filename_kernel, filename)(name);
821 return do_open_execat(AT_FDCWD, filename, 0);
822}
823EXPORT_SYMBOL(open_exec);
824
825#if defined(CONFIG_BINFMT_FLAT) || defined(CONFIG_BINFMT_ELF_FDPIC)
826ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
827{
828 ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
829 if (res > 0)
830 flush_icache_user_range(addr, addr + len);
831 return res;
832}
833EXPORT_SYMBOL(read_code);
834#endif
835
836/*
837 * Maps the mm_struct mm into the current task struct.
838 * On success, this function returns with exec_update_lock
839 * held for writing. The replaced address space is stashed in
840 * bprm->old_mm for setup_new_exec() to release outside the lock.
841 */
842static int exec_mmap(struct linux_binprm *bprm)
843{
844 struct task_exec_state *exec_state __free(put_task_exec_state) = NULL;
845 struct mm_struct *mm = bprm->mm;
846 struct task_struct *tsk;
847 struct mm_struct *old_mm, *active_mm;
848 int ret;
849
850 exec_state = alloc_task_exec_state(bprm->user_ns);
851 if (!exec_state)
852 return -ENOMEM;
853
854 /* Notify parent that we're no longer interested in the old VM */
855 tsk = current;
856 old_mm = current->mm;
857 exec_mm_release(tsk, old_mm);
858
859 ret = down_write_killable(&tsk->signal->exec_update_lock);
860 if (ret)
861 return ret;
862
863 if (old_mm) {
864 /*
865 * If there is a pending fatal signal perhaps a signal
866 * whose default action is to create a coredump get
867 * out and die instead of going through with the exec.
868 */
869 ret = mmap_read_lock_killable(old_mm);
870 if (ret) {
871 up_write(&tsk->signal->exec_update_lock);
872 return ret;
873 }
874 }
875
876 task_lock(tsk);
877 membarrier_exec_mmap(mm);
878
879 local_irq_disable();
880 active_mm = tsk->active_mm;
881 tsk->active_mm = mm;
882 tsk->mm = mm;
883 mm_init_cid(mm, tsk);
884 exec_state = task_exec_state_replace(tsk, exec_state);
885 /*
886 * This prevents preemption while active_mm is being loaded and
887 * it and mm are being updated, which could cause problems for
888 * lazy tlb mm refcounting when these are updated by context
889 * switches. Not all architectures can handle irqs off over
890 * activate_mm yet.
891 */
892 if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
893 local_irq_enable();
894 activate_mm(active_mm, mm);
895 if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
896 local_irq_enable();
897 lru_gen_add_mm(mm);
898 task_unlock(tsk);
899 lru_gen_use_mm(mm);
900 if (old_mm) {
901 mmap_read_unlock(old_mm);
902 BUG_ON(active_mm != old_mm);
903 /* Defer teardown to setup_new_exec(), outside the exec locks. */
904 bprm->old_mm = old_mm;
905 return 0;
906 }
907 mmdrop_lazy_tlb(active_mm);
908 return 0;
909}
910
911/* Release the address space replaced by exec, outside the exec locks. */
912static void exec_mm_put_old(struct mm_struct *old_mm)
913{
914 setmax_mm_hiwater_rss(&current->signal->maxrss, old_mm);
915 mm_update_next_owner(old_mm);
916 mmput(old_mm);
917}
918
919static int de_thread(struct task_struct *tsk)
920{
921 struct signal_struct *sig = tsk->signal;
922 struct sighand_struct *oldsighand = tsk->sighand;
923 spinlock_t *lock = &oldsighand->siglock;
924
925 if (thread_group_empty(tsk))
926 goto no_thread_group;
927
928 /*
929 * Kill all other threads in the thread group.
930 */
931 spin_lock_irq(lock);
932 if ((sig->flags & SIGNAL_GROUP_EXIT) || sig->group_exec_task) {
933 /*
934 * Another group action in progress, just
935 * return so that the signal is processed.
936 */
937 spin_unlock_irq(lock);
938 return -EAGAIN;
939 }
940
941 sig->group_exec_task = tsk;
942 sig->notify_count = zap_other_threads(tsk);
943 if (!thread_group_leader(tsk))
944 sig->notify_count--;
945
946 while (sig->notify_count) {
947 __set_current_state(TASK_KILLABLE);
948 spin_unlock_irq(lock);
949 schedule();
950 if (__fatal_signal_pending(tsk))
951 goto killed;
952 spin_lock_irq(lock);
953 }
954 spin_unlock_irq(lock);
955
956 /*
957 * At this point all other threads have exited, all we have to
958 * do is to wait for the thread group leader to become inactive,
959 * and to assume its PID:
960 */
961 if (!thread_group_leader(tsk)) {
962 struct task_struct *leader = tsk->group_leader;
963
964 for (;;) {
965 cgroup_threadgroup_change_begin(tsk);
966 write_lock_irq(&tasklist_lock);
967 /*
968 * Do this under tasklist_lock to ensure that
969 * exit_notify() can't miss ->group_exec_task
970 */
971 sig->notify_count = -1;
972 if (likely(leader->exit_state))
973 break;
974 __set_current_state(TASK_KILLABLE);
975 write_unlock_irq(&tasklist_lock);
976 cgroup_threadgroup_change_end(tsk);
977 schedule();
978 if (__fatal_signal_pending(tsk))
979 goto killed;
980 }
981
982 /*
983 * The only record we have of the real-time age of a
984 * process, regardless of execs it's done, is start_time.
985 * All the past CPU time is accumulated in signal_struct
986 * from sister threads now dead. But in this non-leader
987 * exec, nothing survives from the original leader thread,
988 * whose birth marks the true age of this process now.
989 * When we take on its identity by switching to its PID, we
990 * also take its birthdate (always earlier than our own).
991 */
992 tsk->start_time = leader->start_time;
993 tsk->start_boottime = leader->start_boottime;
994
995 BUG_ON(!same_thread_group(leader, tsk));
996 /*
997 * An exec() starts a new thread group with the
998 * TGID of the previous thread group. Rehash the
999 * two threads with a switched PID, and release
1000 * the former thread group leader:
1001 */
1002
1003 /* Become a process group leader with the old leader's pid.
1004 * The old leader becomes a thread of the this thread group.
1005 */
1006 exchange_tids(tsk, leader);
1007 transfer_pid(leader, tsk, PIDTYPE_TGID);
1008 transfer_pid(leader, tsk, PIDTYPE_PGID);
1009 transfer_pid(leader, tsk, PIDTYPE_SID);
1010
1011 list_replace_rcu(&leader->tasks, &tsk->tasks);
1012 list_replace_init(&leader->sibling, &tsk->sibling);
1013
1014 tsk->group_leader = tsk;
1015 leader->group_leader = tsk;
1016
1017 tsk->exit_signal = SIGCHLD;
1018 leader->exit_signal = -1;
1019
1020 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1021 leader->exit_state = EXIT_DEAD;
1022 /*
1023 * We are going to release_task()->ptrace_unlink() silently,
1024 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1025 * the tracer won't block again waiting for this thread.
1026 */
1027 if (unlikely(leader->ptrace))
1028 __wake_up_parent(leader, leader->parent);
1029 write_unlock_irq(&tasklist_lock);
1030 cgroup_threadgroup_change_end(tsk);
1031
1032 release_task(leader);
1033 }
1034
1035 sig->group_exec_task = NULL;
1036 sig->notify_count = 0;
1037
1038no_thread_group:
1039 /* we have changed execution domain */
1040 tsk->exit_signal = SIGCHLD;
1041
1042 BUG_ON(!thread_group_leader(tsk));
1043 return 0;
1044
1045killed:
1046 /* protects against exit_notify() and __exit_signal() */
1047 read_lock(&tasklist_lock);
1048 sig->group_exec_task = NULL;
1049 sig->notify_count = 0;
1050 read_unlock(&tasklist_lock);
1051 return -EAGAIN;
1052}
1053
1054
1055/*
1056 * This function makes sure the current process has its own signal table,
1057 * so that flush_signal_handlers can later reset the handlers without
1058 * disturbing other processes. (Other processes might share the signal
1059 * table via the CLONE_SIGHAND option to clone().)
1060 */
1061static int unshare_sighand(struct task_struct *me)
1062{
1063 struct sighand_struct *oldsighand = me->sighand;
1064
1065 if (refcount_read(&oldsighand->count) != 1) {
1066 struct sighand_struct *newsighand;
1067 /*
1068 * This ->sighand is shared with the CLONE_SIGHAND
1069 * but not CLONE_THREAD task, switch to the new one.
1070 */
1071 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1072 if (!newsighand)
1073 return -ENOMEM;
1074
1075 refcount_set(&newsighand->count, 1);
1076
1077 write_lock_irq(&tasklist_lock);
1078 spin_lock(&oldsighand->siglock);
1079 memcpy(newsighand->action, oldsighand->action,
1080 sizeof(newsighand->action));
1081 rcu_assign_pointer(me->sighand, newsighand);
1082 spin_unlock(&oldsighand->siglock);
1083 write_unlock_irq(&tasklist_lock);
1084
1085 __cleanup_sighand(oldsighand);
1086 }
1087 return 0;
1088}
1089
1090/*
1091 * This is unlocked -- the string will always be NUL-terminated, but
1092 * may show overlapping contents if racing concurrent reads.
1093 */
1094void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1095{
1096 size_t len = strnlen(buf, sizeof(tsk->comm) - 1);
1097
1098 trace_task_rename(tsk, buf);
1099 memcpy(tsk->comm, buf, len);
1100 memset(&tsk->comm[len], 0, sizeof(tsk->comm) - len);
1101 perf_event_comm(tsk, exec);
1102}
1103
1104/*
1105 * Calling this is the point of no return. None of the failures will be
1106 * seen by userspace since either the process is already taking a fatal
1107 * signal (via de_thread() or coredump), or will have SEGV raised
1108 * (after exec_mmap()) by search_binary_handler (see below).
1109 */
1110int begin_new_exec(struct linux_binprm * bprm)
1111{
1112 struct task_struct *me = current;
1113 int retval;
1114
1115 /* Once we are committed compute the creds */
1116 retval = bprm_creds_from_file(bprm);
1117 if (retval)
1118 return retval;
1119
1120 /*
1121 * This tracepoint marks the point before flushing the old exec where
1122 * the current task is still unchanged, but errors are fatal (point of
1123 * no return). The later "sched_process_exec" tracepoint is called after
1124 * the current task has successfully switched to the new exec.
1125 */
1126 trace_sched_prepare_exec(current, bprm);
1127
1128 /*
1129 * Ensure all future errors are fatal.
1130 */
1131 bprm->point_of_no_return = true;
1132
1133 /* Make this the only thread in the thread group */
1134 retval = de_thread(me);
1135 if (retval)
1136 goto out;
1137 /* see the comment in check_unsafe_exec() */
1138 current->fs->in_exec = 0;
1139 /*
1140 * Cancel any io_uring activity across execve
1141 */
1142 io_uring_task_cancel();
1143
1144 /* Ensure the files table is not shared. */
1145 retval = unshare_files();
1146 if (retval)
1147 goto out;
1148
1149 /*
1150 * Must be called _before_ exec_mmap() as bprm->mm is
1151 * not visible until then. Doing it here also ensures
1152 * we don't race against replace_mm_exe_file().
1153 */
1154 retval = set_mm_exe_file(bprm->mm, bprm->file);
1155 if (retval)
1156 goto out;
1157
1158 /* If the binary is not readable then enforce mm->dumpable=0 */
1159 would_dump(bprm, bprm->file);
1160 if (bprm->have_execfd)
1161 would_dump(bprm, bprm->executable);
1162
1163 /*
1164 * Release all of the old mmap stuff
1165 */
1166 acct_arg_size(bprm, 0);
1167 retval = exec_mmap(bprm);
1168 if (retval)
1169 goto out;
1170
1171 bprm->mm = NULL;
1172
1173 retval = exec_task_namespaces();
1174 if (retval)
1175 goto out_unlock;
1176
1177#ifdef CONFIG_POSIX_TIMERS
1178 spin_lock_irq(&me->sighand->siglock);
1179 posix_cpu_timers_exit(me);
1180 spin_unlock_irq(&me->sighand->siglock);
1181 exit_itimers(me);
1182 flush_itimer_signals();
1183#endif
1184
1185 /*
1186 * Make the signal table private.
1187 */
1188 retval = unshare_sighand(me);
1189 if (retval)
1190 goto out_unlock;
1191
1192 me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC |
1193 PF_NOFREEZE | PF_NO_SETAFFINITY);
1194 flush_thread();
1195 me->personality &= ~bprm->per_clear;
1196
1197 clear_syscall_work_syscall_user_dispatch(me);
1198
1199 /*
1200 * We have to apply CLOEXEC before we change whether the process is
1201 * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1202 * trying to access the should-be-closed file descriptors of a process
1203 * undergoing exec(2).
1204 */
1205 do_close_on_exec(me->files);
1206
1207 if (bprm->secureexec) {
1208 /* Make sure parent cannot signal privileged process. */
1209 me->pdeath_signal = 0;
1210
1211 /*
1212 * For secureexec, reset the stack limit to sane default to
1213 * avoid bad behavior from the prior rlimits. This has to
1214 * happen before arch_pick_mmap_layout(), which examines
1215 * RLIMIT_STACK, but after the point of no return to avoid
1216 * needing to clean up the change on failure.
1217 */
1218 if (bprm->rlim_stack.rlim_cur > _STK_LIM)
1219 bprm->rlim_stack.rlim_cur = _STK_LIM;
1220 }
1221
1222 me->sas_ss_sp = me->sas_ss_size = 0;
1223
1224 /*
1225 * Figure out dumpability. Note that this checking only of current
1226 * is wrong, but userspace depends on it. This should be testing
1227 * bprm->secureexec instead.
1228 */
1229 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
1230 !(uid_eq(current_euid(), current_uid()) &&
1231 gid_eq(current_egid(), current_gid())))
1232 task_exec_state_set_dumpable(suid_dumpable);
1233 else
1234 task_exec_state_set_dumpable(TASK_DUMPABLE_OWNER);
1235
1236 perf_event_exec();
1237
1238 /*
1239 * If the original filename was empty, alloc_bprm() made up a path
1240 * that will probably not be useful to admins running ps or similar.
1241 * Let's fix it up to be something reasonable.
1242 */
1243 if (bprm->comm_from_dentry) {
1244 /*
1245 * Hold RCU lock to keep the name from being freed behind our back.
1246 * Use acquire semantics to make sure the terminating NUL from
1247 * __d_alloc() is seen.
1248 *
1249 * Note, we're deliberately sloppy here. We don't need to care about
1250 * detecting a concurrent rename and just want a terminated name.
1251 */
1252 rcu_read_lock();
1253 __set_task_comm(me, smp_load_acquire(&bprm->file->f_path.dentry->d_name.name),
1254 true);
1255 rcu_read_unlock();
1256 } else {
1257 __set_task_comm(me, kbasename(bprm->filename), true);
1258 }
1259
1260 /* An exec changes our domain. We are no longer part of the thread
1261 group */
1262 WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1);
1263 flush_signal_handlers(me, 0);
1264
1265 retval = set_cred_ucounts(bprm->cred);
1266 if (retval < 0)
1267 goto out_unlock;
1268
1269 /*
1270 * install the new credentials for this executable
1271 */
1272 security_bprm_committing_creds(bprm);
1273
1274 commit_creds(bprm->cred);
1275 bprm->cred = NULL;
1276
1277 /*
1278 * Disable monitoring for regular users
1279 * when executing setuid binaries. Must
1280 * wait until new credentials are committed
1281 * by commit_creds() above
1282 */
1283 if (task_exec_state_get_dumpable(me) != TASK_DUMPABLE_OWNER)
1284 perf_event_exit_task(me);
1285 /*
1286 * cred_guard_mutex must be held at least to this point to prevent
1287 * ptrace_attach() from altering our determination of the task's
1288 * credentials; any time after this it may be unlocked.
1289 */
1290 security_bprm_committed_creds(bprm);
1291
1292 /* Pass the opened binary to the interpreter. */
1293 if (bprm->have_execfd) {
1294 retval = FD_ADD(0, bprm->executable);
1295 if (retval < 0)
1296 goto out_unlock;
1297 bprm->executable = NULL;
1298 bprm->execfd = retval;
1299 }
1300 return 0;
1301
1302out_unlock:
1303 up_write(&me->signal->exec_update_lock);
1304 if (!bprm->cred)
1305 mutex_unlock(&me->signal->cred_guard_mutex);
1306
1307out:
1308 return retval;
1309}
1310EXPORT_SYMBOL(begin_new_exec);
1311
1312void would_dump(struct linux_binprm *bprm, struct file *file)
1313{
1314 struct inode *inode = file_inode(file);
1315 struct mnt_idmap *idmap = file_mnt_idmap(file);
1316 if (inode_permission(idmap, inode, MAY_READ) < 0) {
1317 struct user_namespace *old, *user_ns;
1318 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1319
1320 /* Ensure bprm->user_ns contains the executable. */
1321 user_ns = old = bprm->user_ns;
1322 while ((user_ns != &init_user_ns) &&
1323 !privileged_wrt_inode_uidgid(user_ns, idmap, inode))
1324 user_ns = user_ns->parent;
1325
1326 if (old != user_ns) {
1327 bprm->user_ns = get_user_ns(user_ns);
1328 put_user_ns(old);
1329 }
1330 }
1331}
1332EXPORT_SYMBOL(would_dump);
1333
1334void setup_new_exec(struct linux_binprm * bprm)
1335{
1336 /* Setup things that can depend upon the personality */
1337 struct task_struct *me = current;
1338
1339 arch_pick_mmap_layout(me->mm, &bprm->rlim_stack);
1340
1341 arch_setup_new_exec();
1342
1343 /* Set the new mm task size. We have to do that late because it may
1344 * depend on TIF_32BIT which is only updated in flush_thread() on
1345 * some architectures like powerpc
1346 */
1347 me->mm->task_size = TASK_SIZE;
1348 up_write(&me->signal->exec_update_lock);
1349 mutex_unlock(&me->signal->cred_guard_mutex);
1350
1351 /* The exec locks are dropped: release the old address space now. */
1352 if (bprm->old_mm) {
1353 exec_mm_put_old(bprm->old_mm);
1354 bprm->old_mm = NULL;
1355 }
1356}
1357EXPORT_SYMBOL(setup_new_exec);
1358
1359/* Runs immediately before start_thread() takes over. */
1360void finalize_exec(struct linux_binprm *bprm)
1361{
1362 /* Store any stack rlimit changes before starting thread. */
1363 task_lock(current->group_leader);
1364 current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack;
1365 task_unlock(current->group_leader);
1366}
1367EXPORT_SYMBOL(finalize_exec);
1368
1369/*
1370 * Prepare credentials and lock ->cred_guard_mutex.
1371 * setup_new_exec() commits the new creds and drops the lock.
1372 * Or, if exec fails before, free_bprm() should release ->cred
1373 * and unlock.
1374 */
1375static int prepare_bprm_creds(struct linux_binprm *bprm)
1376{
1377 if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1378 return -ERESTARTNOINTR;
1379
1380 bprm->cred = prepare_exec_creds();
1381 if (likely(bprm->cred))
1382 return 0;
1383
1384 mutex_unlock(&current->signal->cred_guard_mutex);
1385 return -ENOMEM;
1386}
1387
1388/* Matches do_open_execat() */
1389static void do_close_execat(struct file *file)
1390{
1391 if (!file)
1392 return;
1393 exe_file_allow_write_access(file);
1394 fput(file);
1395}
1396
1397static void free_bprm(struct linux_binprm *bprm)
1398{
1399 if (bprm->mm) {
1400 acct_arg_size(bprm, 0);
1401 mmput(bprm->mm);
1402 }
1403 if (bprm->user_ns)
1404 put_user_ns(bprm->user_ns);
1405 free_arg_pages(bprm);
1406 if (bprm->cred) {
1407 /* in case exec fails before de_thread() succeeds */
1408 current->fs->in_exec = 0;
1409 mutex_unlock(&current->signal->cred_guard_mutex);
1410 abort_creds(bprm->cred);
1411 }
1412 /* exec swapped the mm but failed before setup_new_exec() freed it */
1413 if (bprm->old_mm)
1414 exec_mm_put_old(bprm->old_mm);
1415 do_close_execat(bprm->file);
1416 if (bprm->executable)
1417 fput(bprm->executable);
1418 /* If a binfmt changed the interp, free it. */
1419 if (bprm->interp != bprm->filename)
1420 kfree(bprm->interp);
1421 kfree(bprm->fdpath);
1422 kfree(bprm);
1423}
1424
1425static struct linux_binprm *alloc_bprm(int fd, struct filename *filename, int flags)
1426{
1427 struct linux_binprm *bprm;
1428 struct file *file;
1429 int retval = -ENOMEM;
1430
1431 file = do_open_execat(fd, filename, flags);
1432 if (IS_ERR(file))
1433 return ERR_CAST(file);
1434
1435 bprm = kzalloc_obj(*bprm);
1436 if (!bprm) {
1437 do_close_execat(file);
1438 return ERR_PTR(-ENOMEM);
1439 }
1440
1441 bprm->file = file;
1442
1443 if (fd == AT_FDCWD || filename->name[0] == '/') {
1444 bprm->filename = filename->name;
1445 } else {
1446 if (filename->name[0] == '\0') {
1447 bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd);
1448 bprm->comm_from_dentry = 1;
1449 } else {
1450 bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s",
1451 fd, filename->name);
1452 }
1453 if (!bprm->fdpath)
1454 goto out_free;
1455
1456 /*
1457 * Record that a name derived from an O_CLOEXEC fd will be
1458 * inaccessible after exec. This allows the code in exec to
1459 * choose to fail when the executable is not mmaped into the
1460 * interpreter and an open file descriptor is not passed to
1461 * the interpreter. This makes for a better user experience
1462 * than having the interpreter start and then immediately fail
1463 * when it finds the executable is inaccessible.
1464 */
1465 if (get_close_on_exec(fd))
1466 bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1467
1468 bprm->filename = bprm->fdpath;
1469 }
1470 bprm->interp = bprm->filename;
1471
1472 /*
1473 * At this point, security_file_open() has already been called (with
1474 * __FMODE_EXEC) and access control checks for AT_EXECVE_CHECK will
1475 * stop just after the security_bprm_creds_for_exec() call in
1476 * bprm_execve(). Indeed, the kernel should not try to parse the
1477 * content of the file with exec_binprm() nor change the calling
1478 * thread, which means that the following security functions will not
1479 * be called:
1480 * - security_bprm_check()
1481 * - security_bprm_creds_from_file()
1482 * - security_bprm_committing_creds()
1483 * - security_bprm_committed_creds()
1484 */
1485 bprm->is_check = !!(flags & AT_EXECVE_CHECK);
1486
1487 retval = bprm_mm_init(bprm);
1488 if (!retval)
1489 return bprm;
1490
1491out_free:
1492 free_bprm(bprm);
1493 return ERR_PTR(retval);
1494}
1495
1496DEFINE_CLASS(bprm, struct linux_binprm *, if (!IS_ERR(_T)) free_bprm(_T),
1497 alloc_bprm(fd, name, flags), int fd, struct filename *name, int flags)
1498
1499int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
1500{
1501 /* If a binfmt changed the interp, free it first. */
1502 if (bprm->interp != bprm->filename)
1503 kfree(bprm->interp);
1504 bprm->interp = kstrdup(interp, GFP_KERNEL);
1505 if (!bprm->interp)
1506 return -ENOMEM;
1507 return 0;
1508}
1509EXPORT_SYMBOL(bprm_change_interp);
1510
1511/*
1512 * determine how safe it is to execute the proposed program
1513 * - the caller must hold ->cred_guard_mutex to protect against
1514 * PTRACE_ATTACH or seccomp thread-sync
1515 */
1516static void check_unsafe_exec(struct linux_binprm *bprm)
1517{
1518 struct task_struct *p = current, *t;
1519 unsigned n_fs;
1520
1521 if (p->ptrace)
1522 bprm->unsafe |= LSM_UNSAFE_PTRACE;
1523
1524 /*
1525 * This isn't strictly necessary, but it makes it harder for LSMs to
1526 * mess up.
1527 */
1528 if (task_no_new_privs(current))
1529 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1530
1531 /*
1532 * If another task is sharing our fs, we cannot safely
1533 * suid exec because the differently privileged task
1534 * will be able to manipulate the current directory, etc.
1535 * It would be nice to force an unshare instead...
1536 *
1537 * Otherwise we set fs->in_exec = 1 to deny clone(CLONE_FS)
1538 * from another sub-thread until de_thread() succeeds, this
1539 * state is protected by cred_guard_mutex we hold.
1540 */
1541 n_fs = 1;
1542 read_seqlock_excl(&p->fs->seq);
1543 rcu_read_lock();
1544 for_other_threads(p, t) {
1545 if (t->fs == p->fs)
1546 n_fs++;
1547 }
1548 rcu_read_unlock();
1549
1550 /* "users" and "in_exec" locked for copy_fs() */
1551 if (p->fs->users > n_fs)
1552 bprm->unsafe |= LSM_UNSAFE_SHARE;
1553 else
1554 p->fs->in_exec = 1;
1555 read_sequnlock_excl(&p->fs->seq);
1556}
1557
1558static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
1559{
1560 /* Handle suid and sgid on files */
1561 struct mnt_idmap *idmap;
1562 struct inode *inode = file_inode(file);
1563 unsigned int mode;
1564 vfsuid_t vfsuid;
1565 vfsgid_t vfsgid;
1566 int err;
1567
1568 if (!mnt_may_suid(file->f_path.mnt))
1569 return;
1570
1571 if (task_no_new_privs(current))
1572 return;
1573
1574 mode = READ_ONCE(inode->i_mode);
1575 if (!(mode & (S_ISUID|S_ISGID)))
1576 return;
1577
1578 idmap = file_mnt_idmap(file);
1579
1580 /* Be careful if suid/sgid is set */
1581 inode_lock(inode);
1582
1583 /* Atomically reload and check mode/uid/gid now that lock held. */
1584 mode = inode->i_mode;
1585 vfsuid = i_uid_into_vfsuid(idmap, inode);
1586 vfsgid = i_gid_into_vfsgid(idmap, inode);
1587 err = inode_permission(idmap, inode, MAY_EXEC);
1588 inode_unlock(inode);
1589
1590 /* Did the exec bit vanish out from under us? Give up. */
1591 if (err)
1592 return;
1593
1594 /* We ignore suid/sgid if there are no mappings for them in the ns */
1595 if (!vfsuid_has_mapping(bprm->cred->user_ns, vfsuid) ||
1596 !vfsgid_has_mapping(bprm->cred->user_ns, vfsgid))
1597 return;
1598
1599 if (mode & S_ISUID) {
1600 bprm->per_clear |= PER_CLEAR_ON_SETID;
1601 bprm->cred->euid = vfsuid_into_kuid(vfsuid);
1602 }
1603
1604 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1605 bprm->per_clear |= PER_CLEAR_ON_SETID;
1606 bprm->cred->egid = vfsgid_into_kgid(vfsgid);
1607 }
1608}
1609
1610/*
1611 * Compute brpm->cred based upon the final binary.
1612 */
1613static int bprm_creds_from_file(struct linux_binprm *bprm)
1614{
1615 /* Compute creds based on which file? */
1616 struct file *file = bprm->execfd_creds ? bprm->executable : bprm->file;
1617
1618 bprm_fill_uid(bprm, file);
1619 return security_bprm_creds_from_file(bprm, file);
1620}
1621
1622/*
1623 * Fill the binprm structure from the inode.
1624 * Read the first BINPRM_BUF_SIZE bytes
1625 *
1626 * This may be called multiple times for binary chains (scripts for example).
1627 */
1628static int prepare_binprm(struct linux_binprm *bprm)
1629{
1630 loff_t pos = 0;
1631
1632 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1633 return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
1634}
1635
1636/*
1637 * Arguments are '\0' separated strings found at the location bprm->p
1638 * points to; chop off the first by relocating brpm->p to right after
1639 * the first '\0' encountered.
1640 */
1641int remove_arg_zero(struct linux_binprm *bprm)
1642{
1643 unsigned long offset;
1644 char *kaddr;
1645 struct page *page;
1646
1647 if (!bprm->argc)
1648 return 0;
1649
1650 do {
1651 offset = bprm->p & ~PAGE_MASK;
1652 page = get_arg_page(bprm, bprm->p, 0);
1653 if (!page)
1654 return -EFAULT;
1655 kaddr = kmap_local_page(page);
1656
1657 for (; offset < PAGE_SIZE && kaddr[offset];
1658 offset++, bprm->p++)
1659 ;
1660
1661 kunmap_local(kaddr);
1662 put_arg_page(page);
1663 } while (offset == PAGE_SIZE);
1664
1665 bprm->p++;
1666 bprm->argc--;
1667
1668 return 0;
1669}
1670EXPORT_SYMBOL(remove_arg_zero);
1671
1672/*
1673 * cycle the list of binary formats handler, until one recognizes the image
1674 */
1675static int search_binary_handler(struct linux_binprm *bprm)
1676{
1677 struct linux_binfmt *fmt;
1678 int retval;
1679
1680 retval = prepare_binprm(bprm);
1681 if (retval < 0)
1682 return retval;
1683
1684 retval = security_bprm_check(bprm);
1685 if (retval)
1686 return retval;
1687
1688 read_lock(&binfmt_lock);
1689 list_for_each_entry(fmt, &formats, lh) {
1690 if (!try_module_get(fmt->module))
1691 continue;
1692 read_unlock(&binfmt_lock);
1693
1694 retval = fmt->load_binary(bprm);
1695
1696 read_lock(&binfmt_lock);
1697 put_binfmt(fmt);
1698 if (bprm->point_of_no_return || (retval != -ENOEXEC)) {
1699 read_unlock(&binfmt_lock);
1700 return retval;
1701 }
1702 }
1703 read_unlock(&binfmt_lock);
1704
1705 return -ENOEXEC;
1706}
1707
1708/* binfmt handlers will call back into begin_new_exec() on success. */
1709static int exec_binprm(struct linux_binprm *bprm)
1710{
1711 pid_t old_pid, old_vpid;
1712 int ret, depth;
1713
1714 /* Need to fetch pid before load_binary changes it */
1715 old_pid = current->pid;
1716 rcu_read_lock();
1717 old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1718 rcu_read_unlock();
1719
1720 /* This allows 5 levels of binfmt rewrites before failing hard. */
1721 for (depth = 0;; depth++) {
1722 struct file *exec;
1723 if (depth > 5)
1724 return -ELOOP;
1725
1726 ret = search_binary_handler(bprm);
1727 if (ret < 0)
1728 return ret;
1729 if (!bprm->interpreter)
1730 break;
1731
1732 exec = bprm->file;
1733 bprm->file = bprm->interpreter;
1734 bprm->interpreter = NULL;
1735
1736 exe_file_allow_write_access(exec);
1737 if (unlikely(bprm->have_execfd)) {
1738 if (bprm->executable) {
1739 fput(exec);
1740 return -ENOEXEC;
1741 }
1742 bprm->executable = exec;
1743 } else
1744 fput(exec);
1745 }
1746
1747 audit_bprm(bprm);
1748 trace_sched_process_exec(current, old_pid, bprm);
1749 ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1750 proc_exec_connector(current);
1751 return 0;
1752}
1753
1754static int bprm_execve(struct linux_binprm *bprm)
1755{
1756 int retval;
1757
1758 retval = prepare_bprm_creds(bprm);
1759 if (retval)
1760 return retval;
1761
1762 /*
1763 * Check for unsafe execution states before exec_binprm(), which
1764 * will call back into begin_new_exec(), into bprm_creds_from_file(),
1765 * where setuid-ness is evaluated.
1766 */
1767 check_unsafe_exec(bprm);
1768 current->in_execve = 1;
1769 sched_mm_cid_before_execve(current);
1770
1771 sched_exec();
1772
1773 /* Set the unchanging part of bprm->cred */
1774 retval = security_bprm_creds_for_exec(bprm);
1775 if (retval || bprm->is_check)
1776 goto out;
1777
1778 retval = exec_binprm(bprm);
1779 if (retval < 0)
1780 goto out;
1781
1782 sched_mm_cid_after_execve(current);
1783 rseq_execve(current);
1784 /* execve succeeded */
1785 current->in_execve = 0;
1786 user_events_execve(current);
1787 acct_update_integrals(current);
1788 task_numa_free(current, false);
1789 return retval;
1790
1791out:
1792 /*
1793 * If past the point of no return ensure the code never
1794 * returns to the userspace process. Use an existing fatal
1795 * signal if present otherwise terminate the process with
1796 * SIGSEGV.
1797 */
1798 if (bprm->point_of_no_return && !fatal_signal_pending(current))
1799 force_fatal_sig(SIGSEGV);
1800
1801 sched_mm_cid_after_execve(current);
1802 rseq_force_update();
1803 current->in_execve = 0;
1804
1805 return retval;
1806}
1807
1808static int do_execveat_common(int fd, struct filename *filename,
1809 struct user_arg_ptr argv,
1810 struct user_arg_ptr envp,
1811 int flags)
1812{
1813 int retval;
1814
1815 /*
1816 * We move the actual failure in case of RLIMIT_NPROC excess from
1817 * set*uid() to execve() because too many poorly written programs
1818 * don't check setuid() return code. Here we additionally recheck
1819 * whether NPROC limit is still exceeded.
1820 */
1821 if ((current->flags & PF_NPROC_EXCEEDED) &&
1822 is_rlimit_overlimit(current_ucounts(), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC)))
1823 return -EAGAIN;
1824
1825 /* We're below the limit (still or again), so we don't want to make
1826 * further execve() calls fail. */
1827 current->flags &= ~PF_NPROC_EXCEEDED;
1828
1829 CLASS(bprm, bprm)(fd, filename, flags);
1830 if (IS_ERR(bprm))
1831 return PTR_ERR(bprm);
1832
1833 retval = count(argv, MAX_ARG_STRINGS);
1834 if (retval < 0)
1835 return retval;
1836 bprm->argc = retval;
1837
1838 retval = count(envp, MAX_ARG_STRINGS);
1839 if (retval < 0)
1840 return retval;
1841 bprm->envc = retval;
1842
1843 retval = bprm_stack_limits(bprm);
1844 if (retval < 0)
1845 return retval;
1846
1847 retval = copy_string_kernel(bprm->filename, bprm);
1848 if (retval < 0)
1849 return retval;
1850 bprm->exec = bprm->p;
1851
1852 retval = copy_strings(bprm->envc, envp, bprm);
1853 if (retval < 0)
1854 return retval;
1855
1856 retval = copy_strings(bprm->argc, argv, bprm);
1857 if (retval < 0)
1858 return retval;
1859
1860 /*
1861 * When argv is empty, add an empty string ("") as argv[0] to
1862 * ensure confused userspace programs that start processing
1863 * from argv[1] won't end up walking envp. See also
1864 * bprm_stack_limits().
1865 */
1866 if (bprm->argc == 0) {
1867 retval = copy_string_kernel("", bprm);
1868 if (retval < 0)
1869 return retval;
1870 bprm->argc = 1;
1871
1872 pr_warn_once("process '%s' launched '%s' with NULL argv: empty string added\n",
1873 current->comm, bprm->filename);
1874 }
1875
1876 return bprm_execve(bprm);
1877}
1878
1879int kernel_execve(const char *kernel_filename,
1880 const char *const *argv, const char *const *envp)
1881{
1882 int retval;
1883
1884 /* It is non-sense for kernel threads to call execve */
1885 if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
1886 return -EINVAL;
1887
1888 CLASS(filename_kernel, filename)(kernel_filename);
1889 CLASS(bprm, bprm)(AT_FDCWD, filename, 0);
1890 if (IS_ERR(bprm))
1891 return PTR_ERR(bprm);
1892
1893 retval = count_strings_kernel(argv);
1894 if (WARN_ON_ONCE(retval == 0))
1895 return -EINVAL;
1896 if (retval < 0)
1897 return retval;
1898 bprm->argc = retval;
1899
1900 retval = count_strings_kernel(envp);
1901 if (retval < 0)
1902 return retval;
1903 bprm->envc = retval;
1904
1905 retval = bprm_stack_limits(bprm);
1906 if (retval < 0)
1907 return retval;
1908
1909 retval = copy_string_kernel(bprm->filename, bprm);
1910 if (retval < 0)
1911 return retval;
1912 bprm->exec = bprm->p;
1913
1914 retval = copy_strings_kernel(bprm->envc, envp, bprm);
1915 if (retval < 0)
1916 return retval;
1917
1918 retval = copy_strings_kernel(bprm->argc, argv, bprm);
1919 if (retval < 0)
1920 return retval;
1921
1922 return bprm_execve(bprm);
1923}
1924
1925void set_binfmt(struct linux_binfmt *new)
1926{
1927 struct mm_struct *mm = current->mm;
1928
1929 if (mm->binfmt)
1930 module_put(mm->binfmt->module);
1931
1932 mm->binfmt = new;
1933 if (new)
1934 __module_get(new->module);
1935}
1936EXPORT_SYMBOL(set_binfmt);
1937
1938static inline struct user_arg_ptr native_arg(const char __user *const __user *p)
1939{
1940 return (struct user_arg_ptr){.ptr.native = p};
1941}
1942
1943SYSCALL_DEFINE3(execve,
1944 const char __user *, filename,
1945 const char __user *const __user *, argv,
1946 const char __user *const __user *, envp)
1947{
1948 CLASS(filename, name)(filename);
1949 return do_execveat_common(AT_FDCWD, name,
1950 native_arg(argv), native_arg(envp), 0);
1951}
1952
1953SYSCALL_DEFINE5(execveat,
1954 int, fd, const char __user *, filename,
1955 const char __user *const __user *, argv,
1956 const char __user *const __user *, envp,
1957 int, flags)
1958{
1959 CLASS(filename_uflags, name)(filename, flags);
1960 return do_execveat_common(fd, name,
1961 native_arg(argv), native_arg(envp), flags);
1962}
1963
1964#ifdef CONFIG_COMPAT
1965
1966static inline struct user_arg_ptr compat_arg(const compat_uptr_t __user *p)
1967{
1968 return (struct user_arg_ptr){.is_compat = true, .ptr.compat = p};
1969}
1970
1971COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
1972 const compat_uptr_t __user *, argv,
1973 const compat_uptr_t __user *, envp)
1974{
1975 CLASS(filename, name)(filename);
1976 return do_execveat_common(AT_FDCWD, name,
1977 compat_arg(argv), compat_arg(envp), 0);
1978}
1979
1980COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
1981 const char __user *, filename,
1982 const compat_uptr_t __user *, argv,
1983 const compat_uptr_t __user *, envp,
1984 int, flags)
1985{
1986 CLASS(filename_uflags, name)(filename, flags);
1987 return do_execveat_common(fd, name,
1988 compat_arg(argv), compat_arg(envp), flags);
1989}
1990#endif
1991
1992#ifdef CONFIG_SYSCTL
1993
1994static int proc_dointvec_minmax_coredump(const struct ctl_table *table, int write,
1995 void *buffer, size_t *lenp, loff_t *ppos)
1996{
1997 int error, old = READ_ONCE(suid_dumpable);
1998
1999 error = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
2000
2001 if (!error && write && (old != READ_ONCE(suid_dumpable)))
2002 validate_coredump_safety();
2003 return error;
2004}
2005
2006static const struct ctl_table fs_exec_sysctls[] = {
2007 {
2008 .procname = "suid_dumpable",
2009 .data = &suid_dumpable,
2010 .maxlen = sizeof(int),
2011 .mode = 0644,
2012 .proc_handler = proc_dointvec_minmax_coredump,
2013 .extra1 = SYSCTL_ZERO,
2014 .extra2 = SYSCTL_TWO,
2015 },
2016};
2017
2018static int __init init_fs_exec_sysctls(void)
2019{
2020 register_sysctl_init("fs", fs_exec_sysctls);
2021 return 0;
2022}
2023
2024fs_initcall(init_fs_exec_sysctls);
2025#endif /* CONFIG_SYSCTL */
2026
2027#ifdef CONFIG_EXEC_KUNIT_TEST
2028#include "tests/exec_kunit.c"
2029#endif