projects/linux·blob v7.3-rc1 · 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/futex.h>
34#include <linux/swap.h>
35#include <linux/string.h>
36#include <linux/init.h>
37#include <linux/sched/mm.h>
38#include <linux/sched/coredump.h>
39#include <linux/sched/exec_state.h>
40#include <linux/sched/signal.h>
41#include <linux/sched/numa_balancing.h>
42#include <linux/sched/task.h>
43#include <linux/pagemap.h>
44#include <linux/perf_event.h>
45#include <linux/highmem.h>
46#include <linux/spinlock.h>
47#include <linux/key.h>
48#include <linux/personality.h>
49#include <linux/binfmts.h>
50#include <linux/utsname.h>
51#include <linux/pid_namespace.h>
52#include <linux/module.h>
53#include <linux/namei.h>
54#include <linux/mount.h>
55#include <linux/security.h>
56#include <linux/syscalls.h>
57#include <linux/tsacct_kern.h>
58#include <linux/cn_proc.h>
59#include <linux/audit.h>
60#include <linux/kmod.h>
61#include <linux/fsnotify.h>
62#include <linux/fs_struct.h>
63#include <linux/oom.h>
64#include <linux/compat.h>
65#include <linux/vmalloc.h>
66#include <linux/io_uring.h>
67#include <linux/syscall_user_dispatch.h>
68#include <linux/coredump.h>
69#include <linux/time_namespace.h>
70#include <linux/user_events.h>
71#include <linux/rseq.h>
72#include <linux/ksm.h>
73
74#include <linux/uaccess.h>
75#include <asm/mmu_context.h>
76#include <asm/tlb.h>
77
78#include <trace/events/task.h>
79#include "internal.h"
80
81#include <trace/events/sched.h>
82
83/* For vma exec functions. */
84#include "../mm/internal.h"
85
86static int bprm_creds_from_file(struct linux_binprm *bprm);
87
88int suid_dumpable = 0;
89
90static LIST_HEAD(formats);
91static DEFINE_RWLOCK(binfmt_lock);
92
93void __register_binfmt(struct linux_binfmt * fmt, int insert)
94{
95 write_lock(&binfmt_lock);
96 insert ? list_add(&fmt->lh, &formats) :
97 list_add_tail(&fmt->lh, &formats);
98 write_unlock(&binfmt_lock);
99}
100
101EXPORT_SYMBOL(__register_binfmt);
102
103void unregister_binfmt(struct linux_binfmt * fmt)
104{
105 write_lock(&binfmt_lock);
106 list_del(&fmt->lh);
107 write_unlock(&binfmt_lock);
108}
109
110EXPORT_SYMBOL(unregister_binfmt);
111
112static inline void put_binfmt(struct linux_binfmt * fmt)
113{
114 module_put(fmt->module);
115}
116
117bool path_noexec(const struct path *path)
118{
119 /* If it's an anonymous inode make sure that we catch any shenanigans. */
120 VFS_WARN_ON_ONCE(IS_ANON_FILE(d_inode(path->dentry)) &&
121 !(path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC));
122 return (path->mnt->mnt_flags & MNT_NOEXEC) ||
123 (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
124}
125
126#ifdef CONFIG_MMU
127/*
128 * The nascent bprm->mm is not visible until exec_mmap() but it can
129 * use a lot of memory, account these pages in current->mm temporary
130 * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
131 * change the counter back via acct_arg_size(0).
132 */
133static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
134{
135 struct mm_struct *mm = current->mm;
136 long diff = (long)(pages - bprm->vma_pages);
137
138 if (!mm || !diff)
139 return;
140
141 bprm->vma_pages = pages;
142 add_mm_counter(mm, MM_ANONPAGES, diff);
143}
144
145static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
146 int write)
147{
148 struct page *page;
149 struct vm_area_struct *vma = bprm->vma;
150 struct mm_struct *mm = bprm->mm;
151 int ret;
152
153 /*
154 * Avoid relying on expanding the stack down in GUP (which
155 * does not work for STACK_GROWSUP anyway), and just do it
156 * ahead of time.
157 */
158 if (!mmap_read_lock_maybe_expand(mm, vma, pos, write))
159 return NULL;
160
161 /*
162 * We are doing an exec(). 'current' is the process
163 * doing the exec and 'mm' is the new process's mm.
164 */
165 ret = get_user_pages_remote(mm, pos, 1,
166 write ? FOLL_WRITE : 0,
167 &page, NULL);
168 mmap_read_unlock(mm);
169 if (ret <= 0)
170 return NULL;
171
172 if (write)
173 acct_arg_size(bprm, vma_pages(vma));
174
175 return page;
176}
177
178static void put_arg_page(struct page *page)
179{
180 put_page(page);
181}
182
183static void free_arg_pages(struct linux_binprm *bprm)
184{
185}
186
187static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
188 struct page *page)
189{
190 flush_cache_page(bprm->vma, pos, page_to_pfn(page));
191}
192
193static bool valid_arg_len(struct linux_binprm *bprm, long len)
194{
195 return len <= MAX_ARG_STRLEN;
196}
197
198#else
199
200static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
201{
202}
203
204static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
205 int write)
206{
207 struct page *page;
208
209 page = bprm->page[pos / PAGE_SIZE];
210 if (!page && write) {
211 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
212 if (!page)
213 return NULL;
214 bprm->page[pos / PAGE_SIZE] = page;
215 }
216
217 return page;
218}
219
220static void put_arg_page(struct page *page)
221{
222}
223
224static void free_arg_page(struct linux_binprm *bprm, int i)
225{
226 if (bprm->page[i]) {
227 __free_page(bprm->page[i]);
228 bprm->page[i] = NULL;
229 }
230}
231
232static void free_arg_pages(struct linux_binprm *bprm)
233{
234 int i;
235
236 for (i = 0; i < MAX_ARG_PAGES; i++)
237 free_arg_page(bprm, i);
238}
239
240static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
241 struct page *page)
242{
243}
244
245static bool valid_arg_len(struct linux_binprm *bprm, long len)
246{
247 return len <= bprm->p;
248}
249
250#endif /* CONFIG_MMU */
251
252/*
253 * Create a new mm_struct and populate it with a temporary stack
254 * vm_area_struct. We don't have enough context at this point to set the stack
255 * flags, permissions, and offset, so we use temporary values. We'll update
256 * them later in setup_arg_pages().
257 */
258static int bprm_mm_init(struct linux_binprm *bprm)
259{
260 int err;
261 struct mm_struct *mm = NULL;
262
263 bprm->mm = mm = mm_alloc();
264 err = -ENOMEM;
265 if (!mm)
266 goto err;
267
268 /* Staged for would_dump() narrowing; consumed by begin_new_exec(). */
269 bprm->user_ns = get_user_ns(current_user_ns());
270
271 /* Save current stack limit for all calculations made during exec. */
272 task_lock(current->group_leader);
273 bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK];
274 task_unlock(current->group_leader);
275
276#ifndef CONFIG_MMU
277 bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
278#else
279 err = create_init_stack_vma(bprm->mm, &bprm->vma, &bprm->p);
280 if (err)
281 goto err;
282#endif
283
284 return 0;
285
286err:
287 if (mm) {
288 bprm->mm = NULL;
289 mmdrop(mm);
290 }
291
292 return err;
293}
294
295struct user_arg_ptr {
296#ifdef CONFIG_COMPAT
297 bool is_compat;
298#endif
299 union {
300 const char __user *const __user *native;
301#ifdef CONFIG_COMPAT
302 const compat_uptr_t __user *compat;
303#endif
304 } ptr;
305};
306
307static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
308{
309 const char __user *native;
310
311#ifdef CONFIG_COMPAT
312 if (unlikely(argv.is_compat)) {
313 compat_uptr_t compat;
314
315 if (get_user(compat, argv.ptr.compat + nr))
316 return ERR_PTR(-EFAULT);
317
318 return compat_ptr(compat);
319 }
320#endif
321
322 if (get_user(native, argv.ptr.native + nr))
323 return ERR_PTR(-EFAULT);
324
325 return native;
326}
327
328/*
329 * count() counts the number of strings in array ARGV.
330 */
331static int count(struct user_arg_ptr argv, int max)
332{
333 int i = 0;
334
335 if (argv.ptr.native != NULL) {
336 for (;;) {
337 const char __user *p = get_user_arg_ptr(argv, i);
338
339 if (!p)
340 break;
341
342 if (IS_ERR(p))
343 return -EFAULT;
344
345 if (i >= max)
346 return -E2BIG;
347 ++i;
348
349 if (fatal_signal_pending(current))
350 return -ERESTARTNOHAND;
351 cond_resched();
352 }
353 }
354 return i;
355}
356
357static int count_strings_kernel(const char *const *argv)
358{
359 int i;
360
361 if (!argv)
362 return 0;
363
364 for (i = 0; argv[i]; ++i) {
365 if (i >= MAX_ARG_STRINGS)
366 return -E2BIG;
367 if (fatal_signal_pending(current))
368 return -ERESTARTNOHAND;
369 cond_resched();
370 }
371 return i;
372}
373
374static inline int bprm_set_stack_limit(struct linux_binprm *bprm,
375 unsigned long limit)
376{
377#ifdef CONFIG_MMU
378 /* Avoid a pathological bprm->p. */
379 if (bprm->p < limit)
380 return -E2BIG;
381 bprm->argmin = bprm->p - limit;
382#endif
383 return 0;
384}
385static inline bool bprm_hit_stack_limit(struct linux_binprm *bprm)
386{
387#ifdef CONFIG_MMU
388 return bprm->p < bprm->argmin;
389#else
390 return false;
391#endif
392}
393
394/*
395 * Calculate bprm->argmin from:
396 * - _STK_LIM
397 * - ARG_MAX
398 * - bprm->rlim_stack.rlim_cur
399 * - bprm->argc
400 * - bprm->envc
401 * - bprm->p
402 */
403static int bprm_stack_limits(struct linux_binprm *bprm)
404{
405 unsigned long limit, ptr_size;
406
407 /*
408 * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
409 * (whichever is smaller) for the argv+env strings.
410 * This ensures that:
411 * - the remaining binfmt code will not run out of stack space,
412 * - the program will have a reasonable amount of stack left
413 * to work from.
414 */
415 limit = _STK_LIM / 4 * 3;
416 limit = min(limit, bprm->rlim_stack.rlim_cur / 4);
417 /*
418 * We've historically supported up to 32 pages (ARG_MAX)
419 * of argument strings even with small stacks
420 */
421 limit = max_t(unsigned long, limit, ARG_MAX);
422 /* Reject totally pathological counts. */
423 if (bprm->argc < 0 || bprm->envc < 0)
424 return -E2BIG;
425 /*
426 * We must account for the size of all the argv and envp pointers to
427 * the argv and envp strings, since they will also take up space in
428 * the stack. They aren't stored until much later when we can't
429 * signal to the parent that the child has run out of stack space.
430 * Instead, calculate it here so it's possible to fail gracefully.
431 *
432 * In the case of argc = 0, make sure there is space for adding a
433 * empty string (which will bump argc to 1), to ensure confused
434 * userspace programs don't start processing from argv[1], thinking
435 * argc can never be 0, to keep them from walking envp by accident.
436 * See do_execveat_common().
437 */
438 if (check_add_overflow(max(bprm->argc, 1), bprm->envc, &ptr_size) ||
439 check_mul_overflow(ptr_size, sizeof(void *), &ptr_size))
440 return -E2BIG;
441 if (limit <= ptr_size)
442 return -E2BIG;
443 limit -= ptr_size;
444
445 return bprm_set_stack_limit(bprm, limit);
446}
447
448/*
449 * 'copy_strings()' copies argument/environment strings from the old
450 * processes's memory to the new process's stack. The call to get_user_pages()
451 * ensures the destination page is created and not swapped out.
452 */
453static int copy_strings(int argc, struct user_arg_ptr argv,
454 struct linux_binprm *bprm)
455{
456 struct page *kmapped_page = NULL;
457 char *kaddr = NULL;
458 unsigned long kpos = 0;
459 int ret;
460
461 while (argc-- > 0) {
462 const char __user *str;
463 int len;
464 unsigned long pos;
465
466 ret = -EFAULT;
467 str = get_user_arg_ptr(argv, argc);
468 if (IS_ERR(str))
469 goto out;
470
471 len = strnlen_user(str, MAX_ARG_STRLEN);
472 if (!len)
473 goto out;
474
475 ret = -E2BIG;
476 if (!valid_arg_len(bprm, len))
477 goto out;
478
479 /* We're going to work our way backwards. */
480 pos = bprm->p;
481 str += len;
482 bprm->p -= len;
483 if (bprm_hit_stack_limit(bprm))
484 goto out;
485
486 while (len > 0) {
487 int offset, bytes_to_copy;
488
489 if (fatal_signal_pending(current)) {
490 ret = -ERESTARTNOHAND;
491 goto out;
492 }
493 cond_resched();
494
495 offset = pos % PAGE_SIZE;
496 if (offset == 0)
497 offset = PAGE_SIZE;
498
499 bytes_to_copy = offset;
500 if (bytes_to_copy > len)
501 bytes_to_copy = len;
502
503 offset -= bytes_to_copy;
504 pos -= bytes_to_copy;
505 str -= bytes_to_copy;
506 len -= bytes_to_copy;
507
508 if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
509 struct page *page;
510
511 page = get_arg_page(bprm, pos, 1);
512 if (!page) {
513 ret = -E2BIG;
514 goto out;
515 }
516
517 if (kmapped_page) {
518 flush_dcache_page(kmapped_page);
519 kunmap_local(kaddr);
520 put_arg_page(kmapped_page);
521 }
522 kmapped_page = page;
523 kaddr = kmap_local_page(kmapped_page);
524 kpos = pos & PAGE_MASK;
525 flush_arg_page(bprm, kpos, kmapped_page);
526 }
527 if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
528 ret = -EFAULT;
529 goto out;
530 }
531 }
532 }
533 ret = 0;
534out:
535 if (kmapped_page) {
536 flush_dcache_page(kmapped_page);
537 kunmap_local(kaddr);
538 put_arg_page(kmapped_page);
539 }
540 return ret;
541}
542
543/*
544 * Copy and argument/environment string from the kernel to the processes stack.
545 */
546int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
547{
548 int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;
549 unsigned long pos = bprm->p;
550
551 if (len == 0)
552 return -EFAULT;
553 if (!valid_arg_len(bprm, len))
554 return -E2BIG;
555
556 /* We're going to work our way backwards. */
557 arg += len;
558 bprm->p -= len;
559 if (bprm_hit_stack_limit(bprm))
560 return -E2BIG;
561
562 while (len > 0) {
563 unsigned int bytes_to_copy = min(len,
564 min_not_zero(offset_in_page(pos), PAGE_SIZE));
565 struct page *page;
566
567 pos -= bytes_to_copy;
568 arg -= bytes_to_copy;
569 len -= bytes_to_copy;
570
571 page = get_arg_page(bprm, pos, 1);
572 if (!page)
573 return -E2BIG;
574 flush_arg_page(bprm, pos & PAGE_MASK, page);
575 memcpy_to_page(page, offset_in_page(pos), arg, bytes_to_copy);
576 put_arg_page(page);
577 }
578
579 return 0;
580}
581EXPORT_SYMBOL(copy_string_kernel);
582
583static int copy_strings_kernel(int argc, const char *const *argv,
584 struct linux_binprm *bprm)
585{
586 while (argc-- > 0) {
587 int ret = copy_string_kernel(argv[argc], bprm);
588 if (ret < 0)
589 return ret;
590 if (fatal_signal_pending(current))
591 return -ERESTARTNOHAND;
592 cond_resched();
593 }
594 return 0;
595}
596
597#ifdef CONFIG_MMU
598
599/*
600 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
601 * the stack is optionally relocated, and some extra space is added.
602 */
603int setup_arg_pages(struct linux_binprm *bprm,
604 unsigned long stack_top,
605 int executable_stack)
606{
607 int ret;
608 unsigned long stack_shift;
609 struct mm_struct *mm = current->mm;
610 struct vm_area_struct *vma = bprm->vma;
611 struct vm_area_struct *prev = NULL;
612 vm_flags_t vm_flags;
613 unsigned long stack_base;
614 unsigned long stack_size;
615 unsigned long stack_expand;
616 unsigned long rlim_stack;
617 struct mmu_gather tlb;
618 struct vma_iterator vmi;
619
620#ifdef CONFIG_STACK_GROWSUP
621 /* Limit stack size */
622 stack_base = bprm->rlim_stack.rlim_max;
623
624 stack_base = calc_max_stack_size(stack_base);
625
626 /* Add space for stack randomization. */
627 if (current->flags & PF_RANDOMIZE)
628 stack_base += (STACK_RND_MASK << PAGE_SHIFT);
629
630 /* Make sure we didn't let the argument array grow too large. */
631 if (vma->vm_end - vma->vm_start > stack_base)
632 return -ENOMEM;
633
634 stack_base = PAGE_ALIGN(stack_top - stack_base);
635
636 stack_shift = vma->vm_start - stack_base;
637 mm->arg_start = bprm->p - stack_shift;
638 bprm->p = vma->vm_end - stack_shift;
639#else
640 stack_top = arch_align_stack(stack_top);
641 stack_top = PAGE_ALIGN(stack_top);
642
643 if (unlikely(stack_top < mmap_min_addr) ||
644 unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
645 return -ENOMEM;
646
647 stack_shift = vma->vm_end - stack_top;
648
649 bprm->p -= stack_shift;
650 mm->arg_start = bprm->p;
651#endif
652
653 bprm->exec -= stack_shift;
654
655 if (mmap_write_lock_killable(mm))
656 return -EINTR;
657
658 vm_flags = VM_STACK_FLAGS;
659
660 /*
661 * Adjust stack execute permissions; explicitly enable for
662 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
663 * (arch default) otherwise.
664 */
665 if (unlikely(executable_stack == EXSTACK_ENABLE_X))
666 vm_flags |= VM_EXEC;
667 else if (executable_stack == EXSTACK_DISABLE_X)
668 vm_flags &= ~VM_EXEC;
669 vm_flags |= mm->def_flags;
670 vm_flags |= VM_STACK_INCOMPLETE_SETUP;
671
672 vma_iter_init(&vmi, mm, vma->vm_start);
673
674 tlb_gather_mmu(&tlb, mm);
675 ret = mprotect_fixup(&vmi, &tlb, vma, &prev, vma->vm_start, vma->vm_end,
676 vm_flags);
677 tlb_finish_mmu(&tlb);
678
679 if (ret)
680 goto out_unlock;
681 BUG_ON(prev != vma);
682
683 if (unlikely(vm_flags & VM_EXEC)) {
684 pr_warn_once("process '%pD4' started with executable stack\n",
685 bprm->file);
686 }
687
688 /* Move stack pages down in memory. */
689 if (stack_shift) {
690 /*
691 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once
692 * the binfmt code determines where the new stack should reside, we shift it to
693 * its final location.
694 */
695 ret = relocate_vma_down(vma, stack_shift);
696 if (ret)
697 goto out_unlock;
698 }
699
700 /* mprotect_fixup is overkill to remove the temporary stack flags */
701 vm_flags_clear(vma, VM_STACK_INCOMPLETE_SETUP);
702
703 stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
704 stack_size = vma->vm_end - vma->vm_start;
705 /*
706 * Align this down to a page boundary as expand_stack
707 * will align it up.
708 */
709 rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK;
710
711 stack_expand = min(rlim_stack, stack_size + stack_expand);
712
713#ifdef CONFIG_STACK_GROWSUP
714 stack_base = vma->vm_start + stack_expand;
715#else
716 stack_base = vma->vm_end - stack_expand;
717#endif
718 current->mm->start_stack = bprm->p;
719 ret = expand_stack_locked(vma, stack_base);
720 if (ret)
721 ret = -EFAULT;
722
723out_unlock:
724 mmap_write_unlock(mm);
725 return ret;
726}
727EXPORT_SYMBOL(setup_arg_pages);
728
729#else
730
731/*
732 * Transfer the program arguments and environment from the holding pages
733 * onto the stack. The provided stack pointer is adjusted accordingly.
734 */
735int transfer_args_to_stack(struct linux_binprm *bprm,
736 unsigned long *sp_location)
737{
738 unsigned long index, stop, sp;
739 int ret = 0;
740
741 stop = bprm->p >> PAGE_SHIFT;
742 sp = *sp_location;
743
744 for (index = MAX_ARG_PAGES; index-- > stop; ) {
745 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
746 char *src = kmap_local_page(bprm->page[index]) + offset;
747 sp -= PAGE_SIZE - offset;
748 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
749 ret = -EFAULT;
750 kunmap_local(src);
751 if (ret)
752 goto out;
753 }
754
755 bprm->exec += *sp_location - MAX_ARG_PAGES * PAGE_SIZE;
756 *sp_location = sp;
757
758out:
759 return ret;
760}
761EXPORT_SYMBOL(transfer_args_to_stack);
762
763#endif /* CONFIG_MMU */
764
765/*
766 * On success, caller must call do_close_execat() on the returned
767 * struct file to close it.
768 */
769static struct file *do_open_execat(int fd, struct filename *name, int flags)
770{
771 int err;
772 struct file *file __free(fput) = NULL;
773 struct open_flags open_exec_flags = {
774 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
775 .acc_mode = MAY_EXEC,
776 .intent = LOOKUP_OPEN,
777 .lookup_flags = LOOKUP_FOLLOW,
778 };
779
780 if ((flags &
781 ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH | AT_EXECVE_CHECK)) != 0)
782 return ERR_PTR(-EINVAL);
783 if (flags & AT_SYMLINK_NOFOLLOW)
784 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
785
786 file = do_file_open(fd, name, &open_exec_flags);
787 if (IS_ERR(file))
788 return file;
789
790 if (path_noexec(&file->f_path))
791 return ERR_PTR(-EACCES);
792
793 /*
794 * In the past the regular type check was here. It moved to may_open() in
795 * 633fb6ac3980 ("exec: move S_ISREG() check earlier"). Since then it is
796 * an invariant that all non-regular files error out before we get here.
797 */
798 if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode)))
799 return ERR_PTR(-EACCES);
800
801 err = exe_file_deny_write_access(file);
802 if (err)
803 return ERR_PTR(err);
804
805 return no_free_ptr(file);
806}
807
808/**
809 * open_exec - Open a path name for execution
810 *
811 * @name: path name to open with the intent of executing it.
812 *
813 * Returns ERR_PTR on failure or allocated struct file on success.
814 *
815 * As this is a wrapper for the internal do_open_execat(), callers
816 * must call exe_file_allow_write_access() before fput() on release. Also see
817 * do_close_execat().
818 */
819struct file *open_exec(const char *name)
820{
821 CLASS(filename_kernel, filename)(name);
822 return do_open_execat(AT_FDCWD, filename, 0);
823}
824EXPORT_SYMBOL(open_exec);
825
826#if defined(CONFIG_BINFMT_FLAT) || defined(CONFIG_BINFMT_ELF_FDPIC)
827ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
828{
829 ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
830 if (res > 0)
831 flush_icache_user_range(addr, addr + len);
832 return res;
833}
834EXPORT_SYMBOL(read_code);
835#endif
836
837/*
838 * Maps the mm_struct mm into the current task struct.
839 * On success, this function returns with exec_update_lock
840 * held for writing. The replaced address space is stashed in
841 * bprm->old_mm for setup_new_exec() to release outside the lock.
842 */
843static int exec_mmap(struct linux_binprm *bprm)
844{
845 struct task_exec_state *exec_state __free(put_task_exec_state) = NULL;
846 struct mm_struct *mm = bprm->mm;
847 struct task_struct *tsk;
848 struct mm_struct *old_mm, *active_mm;
849 int ret;
850
851 exec_state = alloc_task_exec_state(bprm->user_ns);
852 if (!exec_state)
853 return -ENOMEM;
854
855 /* Notify parent that we're no longer interested in the old VM */
856 tsk = current;
857 old_mm = current->mm;
858 /* Clean up futexes and release the mm */
859 mm_exit_exec_release(tsk, old_mm);
860
861 ret = down_write_killable(&tsk->signal->exec_update_lock);
862 if (ret)
863 return ret;
864
865 if (old_mm) {
866 /*
867 * If there is a pending fatal signal perhaps a signal
868 * whose default action is to create a coredump get
869 * out and die instead of going through with the exec.
870 */
871 ret = mmap_read_lock_killable(old_mm);
872 if (ret) {
873 up_write(&tsk->signal->exec_update_lock);
874 return ret;
875 }
876 }
877
878 task_lock(tsk);
879 membarrier_exec_mmap(mm);
880
881 local_irq_disable();
882 active_mm = tsk->active_mm;
883 tsk->active_mm = mm;
884 tsk->mm = mm;
885 mm_init_cid(mm, tsk);
886 exec_state = task_exec_state_replace(tsk, exec_state);
887 /*
888 * This prevents preemption while active_mm is being loaded and
889 * it and mm are being updated, which could cause problems for
890 * lazy tlb mm refcounting when these are updated by context
891 * switches. Not all architectures can handle irqs off over
892 * activate_mm yet.
893 */
894 if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
895 local_irq_enable();
896 activate_mm(active_mm, mm);
897 if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
898 local_irq_enable();
899 lru_gen_add_mm(mm);
900 task_unlock(tsk);
901 lru_gen_use_mm(mm);
902 if (old_mm) {
903 mmap_read_unlock(old_mm);
904 BUG_ON(active_mm != old_mm);
905 /* Defer teardown to setup_new_exec(), outside the exec locks. */
906 bprm->old_mm = old_mm;
907 } else {
908 mmdrop_lazy_tlb(active_mm);
909 }
910 futex_exec_done(tsk);
911 return 0;
912}
913
914/* Release the address space replaced by exec, outside the exec locks. */
915static void exec_mm_put_old(struct mm_struct *old_mm)
916{
917 setmax_mm_hiwater_rss(&current->signal->maxrss, old_mm);
918 mm_update_next_owner(old_mm);
919 mmput(old_mm);
920}
921
922static int de_thread(struct task_struct *tsk)
923{
924 struct signal_struct *sig = tsk->signal;
925 struct sighand_struct *oldsighand = tsk->sighand;
926 spinlock_t *lock = &oldsighand->siglock;
927
928 if (thread_group_empty(tsk))
929 goto no_thread_group;
930
931 /*
932 * Kill all other threads in the thread group.
933 */
934 spin_lock_irq(lock);
935 if ((sig->flags & SIGNAL_GROUP_EXIT) || sig->group_exec_task) {
936 /*
937 * Another group action in progress, just
938 * return so that the signal is processed.
939 */
940 spin_unlock_irq(lock);
941 return -EAGAIN;
942 }
943
944 sig->group_exec_task = tsk;
945 sig->notify_count = zap_other_threads(tsk);
946 if (!thread_group_leader(tsk))
947 sig->notify_count--;
948
949 while (sig->notify_count) {
950 __set_current_state(TASK_KILLABLE);
951 spin_unlock_irq(lock);
952 schedule();
953 if (__fatal_signal_pending(tsk))
954 goto killed;
955 spin_lock_irq(lock);
956 }
957 spin_unlock_irq(lock);
958
959 /*
960 * At this point all other threads have exited, all we have to
961 * do is to wait for the thread group leader to become inactive,
962 * and to assume its PID:
963 */
964 if (!thread_group_leader(tsk)) {
965 struct task_struct *leader = tsk->group_leader;
966
967 for (;;) {
968 cgroup_threadgroup_change_begin(tsk);
969 write_lock_irq(&tasklist_lock);
970 /*
971 * Do this under tasklist_lock to ensure that
972 * exit_notify() can't miss ->group_exec_task
973 */
974 sig->notify_count = -1;
975 if (likely(leader->exit_state))
976 break;
977 __set_current_state(TASK_KILLABLE);
978 write_unlock_irq(&tasklist_lock);
979 cgroup_threadgroup_change_end(tsk);
980 schedule();
981 if (__fatal_signal_pending(tsk))
982 goto killed;
983 }
984
985 /*
986 * The only record we have of the real-time age of a
987 * process, regardless of execs it's done, is start_time.
988 * All the past CPU time is accumulated in signal_struct
989 * from sister threads now dead. But in this non-leader
990 * exec, nothing survives from the original leader thread,
991 * whose birth marks the true age of this process now.
992 * When we take on its identity by switching to its PID, we
993 * also take its birthdate (always earlier than our own).
994 */
995 tsk->start_time = leader->start_time;
996 tsk->start_boottime = leader->start_boottime;
997
998 BUG_ON(!same_thread_group(leader, tsk));
999 /*
1000 * An exec() starts a new thread group with the
1001 * TGID of the previous thread group. Rehash the
1002 * two threads with a switched PID, and release
1003 * the former thread group leader:
1004 */
1005
1006 /* Become a process group leader with the old leader's pid.
1007 * The old leader becomes a thread of the this thread group.
1008 */
1009 exchange_tids(tsk, leader);
1010 transfer_pid(leader, tsk, PIDTYPE_TGID);
1011 transfer_pid(leader, tsk, PIDTYPE_PGID);
1012 transfer_pid(leader, tsk, PIDTYPE_SID);
1013
1014 list_replace_rcu(&leader->tasks, &tsk->tasks);
1015 list_replace_init(&leader->sibling, &tsk->sibling);
1016
1017 tsk->group_leader = tsk;
1018 leader->group_leader = tsk;
1019
1020 tsk->exit_signal = SIGCHLD;
1021 leader->exit_signal = -1;
1022
1023 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1024 leader->exit_state = EXIT_DEAD;
1025 /*
1026 * We are going to release_task()->ptrace_unlink() silently,
1027 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1028 * the tracer won't block again waiting for this thread.
1029 */
1030 if (unlikely(leader->ptrace))
1031 __wake_up_parent(leader, leader->parent);
1032 write_unlock_irq(&tasklist_lock);
1033 cgroup_threadgroup_change_end(tsk);
1034
1035 release_task(leader);
1036 }
1037
1038 sig->group_exec_task = NULL;
1039 sig->notify_count = 0;
1040
1041no_thread_group:
1042 /* we have changed execution domain */
1043 tsk->exit_signal = SIGCHLD;
1044
1045 BUG_ON(!thread_group_leader(tsk));
1046 return 0;
1047
1048killed:
1049 /* protects against exit_notify() and __exit_signal() */
1050 read_lock(&tasklist_lock);
1051 sig->group_exec_task = NULL;
1052 sig->notify_count = 0;
1053 read_unlock(&tasklist_lock);
1054 return -EAGAIN;
1055}
1056
1057
1058/*
1059 * This function makes sure the current process has its own signal table,
1060 * so that flush_signal_handlers can later reset the handlers without
1061 * disturbing other processes. (Other processes might share the signal
1062 * table via the CLONE_SIGHAND option to clone().)
1063 */
1064static int unshare_sighand(struct task_struct *me)
1065{
1066 struct sighand_struct *oldsighand = me->sighand;
1067
1068 if (refcount_read(&oldsighand->count) != 1) {
1069 struct sighand_struct *newsighand;
1070 /*
1071 * This ->sighand is shared with the CLONE_SIGHAND
1072 * but not CLONE_THREAD task, switch to the new one.
1073 */
1074 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1075 if (!newsighand)
1076 return -ENOMEM;
1077
1078 refcount_set(&newsighand->count, 1);
1079
1080 write_lock_irq(&tasklist_lock);
1081 spin_lock(&oldsighand->siglock);
1082 memcpy(newsighand->action, oldsighand->action,
1083 sizeof(newsighand->action));
1084 rcu_assign_pointer(me->sighand, newsighand);
1085 spin_unlock(&oldsighand->siglock);
1086 write_unlock_irq(&tasklist_lock);
1087
1088 __cleanup_sighand(oldsighand);
1089 }
1090 return 0;
1091}
1092
1093/*
1094 * This is unlocked -- the string will always be NUL-terminated, but
1095 * may show overlapping contents if racing concurrent reads.
1096 */
1097void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1098{
1099 size_t len = strnlen(buf, sizeof(tsk->comm) - 1);
1100
1101 trace_task_rename(tsk, buf);
1102 memcpy(tsk->comm, buf, len);
1103 memset(&tsk->comm[len], 0, sizeof(tsk->comm) - len);
1104 perf_event_comm(tsk, exec);
1105}
1106
1107/*
1108 * The file the process presents as: its exe link and comm. A transparent
1109 * dispatch presents as the binary, which is bprm->executable.
1110 */
1111static struct file *bprm_identity_file(const struct linux_binprm *bprm)
1112{
1113 if (bprm->interp_flags & BINPRM_FLAGS_TRANSPARENT_INTERP)
1114 return bprm->executable;
1115 return bprm->file;
1116}
1117
1118/*
1119 * Calling this is the point of no return. None of the failures will be
1120 * seen by userspace since either the process is already taking a fatal
1121 * signal (via de_thread() or coredump), or will have SEGV raised
1122 * (after exec_mmap()) by search_binary_handler (see below).
1123 */
1124int begin_new_exec(struct linux_binprm * bprm)
1125{
1126 struct task_struct *me = current;
1127 int retval;
1128
1129 /* A pending PT_INTERP substitution this format cannot consume. */
1130 if (bprm->loader)
1131 return -ENOEXEC;
1132
1133 /* Once we are committed compute the creds */
1134 retval = bprm_creds_from_file(bprm);
1135 if (retval)
1136 return retval;
1137
1138 /*
1139 * This tracepoint marks the point before flushing the old exec where
1140 * the current task is still unchanged, but errors are fatal (point of
1141 * no return). The later "sched_process_exec" tracepoint is called after
1142 * the current task has successfully switched to the new exec.
1143 */
1144 trace_sched_prepare_exec(current, bprm);
1145
1146 /*
1147 * Ensure all future errors are fatal.
1148 */
1149 bprm->point_of_no_return = true;
1150
1151 /* Make this the only thread in the thread group */
1152 retval = de_thread(me);
1153 if (retval)
1154 goto out;
1155 /* see the comment in check_unsafe_exec() */
1156 current->fs->in_exec = 0;
1157 /*
1158 * Cancel any io_uring activity across execve
1159 */
1160 io_uring_task_cancel();
1161
1162 /* Ensure the files table is not shared. */
1163 retval = unshare_files();
1164 if (retval)
1165 goto out;
1166
1167 /*
1168 * Must be called _before_ exec_mmap() as bprm->mm is
1169 * not visible until then. Doing it here also ensures
1170 * we don't race against replace_mm_exe_file().
1171 */
1172 retval = set_mm_exe_file(bprm->mm, bprm_identity_file(bprm));
1173 if (retval)
1174 goto out;
1175
1176 /* If the binary is not readable then enforce mm->dumpable=0 */
1177 would_dump(bprm, bprm->file);
1178 if (bprm->have_execfd)
1179 would_dump(bprm, bprm->executable);
1180
1181 /*
1182 * Release all of the old mmap stuff
1183 */
1184 acct_arg_size(bprm, 0);
1185 retval = exec_mmap(bprm);
1186 if (retval)
1187 goto out;
1188
1189 bprm->mm = NULL;
1190
1191 retval = exec_task_namespaces();
1192 if (retval)
1193 goto out_unlock;
1194
1195#ifdef CONFIG_POSIX_TIMERS
1196 spin_lock_irq(&me->sighand->siglock);
1197 posix_cpu_timers_exit(me);
1198 spin_unlock_irq(&me->sighand->siglock);
1199 exit_itimers(me);
1200 flush_itimer_signals();
1201#endif
1202
1203 /*
1204 * Make the signal table private.
1205 */
1206 retval = unshare_sighand(me);
1207 if (retval)
1208 goto out_unlock;
1209
1210 me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC |
1211 PF_NOFREEZE | PF_NO_SETAFFINITY);
1212 flush_thread();
1213 me->personality &= ~bprm->per_clear;
1214
1215 clear_syscall_work_syscall_user_dispatch(me);
1216
1217 /*
1218 * We have to apply CLOEXEC before we change whether the process is
1219 * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1220 * trying to access the should-be-closed file descriptors of a process
1221 * undergoing exec(2).
1222 */
1223 do_close_on_exec(me->files);
1224
1225 if (bprm->secureexec) {
1226 /* Make sure parent cannot signal privileged process. */
1227 me->pdeath_signal = 0;
1228
1229 /*
1230 * For secureexec, reset the stack limit to sane default to
1231 * avoid bad behavior from the prior rlimits. This has to
1232 * happen before arch_pick_mmap_layout(), which examines
1233 * RLIMIT_STACK, but after the point of no return to avoid
1234 * needing to clean up the change on failure.
1235 */
1236 if (bprm->rlim_stack.rlim_cur > _STK_LIM)
1237 bprm->rlim_stack.rlim_cur = _STK_LIM;
1238 }
1239
1240 me->sas_ss_sp = me->sas_ss_size = 0;
1241
1242 /*
1243 * Figure out dumpability. Note that this checking only of current
1244 * is wrong, but userspace depends on it. This should be testing
1245 * bprm->secureexec instead.
1246 */
1247 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
1248 !(uid_eq(current_euid(), current_uid()) &&
1249 gid_eq(current_egid(), current_gid())))
1250 task_exec_state_set_dumpable(suid_dumpable);
1251 else
1252 task_exec_state_set_dumpable(TASK_DUMPABLE_OWNER);
1253
1254 perf_event_exec();
1255
1256 /*
1257 * If the original filename was empty, alloc_bprm() made up a path
1258 * that will probably not be useful to admins running ps or similar.
1259 * Let's fix it up to be something reasonable.
1260 */
1261 if (bprm->comm_from_dentry) {
1262 struct file *comm_file = bprm_identity_file(bprm);
1263
1264 /*
1265 * Hold RCU lock to keep the name from being freed behind our back.
1266 * Use acquire semantics to make sure the terminating NUL from
1267 * __d_alloc() is seen.
1268 *
1269 * Note, we're deliberately sloppy here. We don't need to care about
1270 * detecting a concurrent rename and just want a terminated name.
1271 */
1272 rcu_read_lock();
1273 __set_task_comm(me, smp_load_acquire(&comm_file->f_path.dentry->d_name.name),
1274 true);
1275 rcu_read_unlock();
1276 } else {
1277 __set_task_comm(me, kbasename(bprm->filename), true);
1278 }
1279
1280 /* An exec changes our domain. We are no longer part of the thread
1281 group */
1282 WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1);
1283 flush_signal_handlers(me, 0);
1284
1285 retval = set_cred_ucounts(bprm->cred);
1286 if (retval < 0)
1287 goto out_unlock;
1288
1289 /*
1290 * install the new credentials for this executable
1291 */
1292 security_bprm_committing_creds(bprm);
1293
1294 commit_creds(bprm->cred);
1295 bprm->cred = NULL;
1296
1297 /*
1298 * Disable monitoring for regular users
1299 * when executing setuid binaries. Must
1300 * wait until new credentials are committed
1301 * by commit_creds() above
1302 */
1303 if (task_exec_state_get_dumpable(me) != TASK_DUMPABLE_OWNER)
1304 perf_event_exit_task(me);
1305 /*
1306 * cred_guard_mutex must be held at least to this point to prevent
1307 * ptrace_attach() from altering our determination of the task's
1308 * credentials; any time after this it may be unlocked.
1309 */
1310 security_bprm_committed_creds(bprm);
1311
1312 /* Pass the opened binary to the interpreter. */
1313 if (bprm->have_execfd) {
1314 struct file *executable = bprm->executable;
1315
1316 /* mm->exe_file carries its own write denial now so drop it. */
1317 exe_file_allow_write_access(executable);
1318 bprm->executable = NULL;
1319 retval = FD_ADD(0, executable);
1320 if (retval < 0) {
1321 /* The reference was not consumed. */
1322 fput(executable);
1323 goto out_unlock;
1324 }
1325 bprm->execfd = retval;
1326 }
1327 return 0;
1328
1329out_unlock:
1330 up_write(&me->signal->exec_update_lock);
1331 if (!bprm->cred)
1332 mutex_unlock(&me->signal->cred_guard_mutex);
1333
1334out:
1335 return retval;
1336}
1337EXPORT_SYMBOL(begin_new_exec);
1338
1339void would_dump(struct linux_binprm *bprm, struct file *file)
1340{
1341 struct inode *inode = file_inode(file);
1342 struct mnt_idmap *idmap = file_mnt_idmap(file);
1343 if (inode_permission(idmap, inode, MAY_READ) < 0) {
1344 struct user_namespace *old, *user_ns;
1345 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1346
1347 /* Ensure bprm->user_ns contains the executable. */
1348 user_ns = old = bprm->user_ns;
1349 while ((user_ns != &init_user_ns) &&
1350 !privileged_wrt_inode_uidgid(user_ns, idmap, inode))
1351 user_ns = user_ns->parent;
1352
1353 if (old != user_ns) {
1354 bprm->user_ns = get_user_ns(user_ns);
1355 put_user_ns(old);
1356 }
1357 }
1358}
1359EXPORT_SYMBOL(would_dump);
1360
1361void setup_new_exec(struct linux_binprm * bprm)
1362{
1363 /* Setup things that can depend upon the personality */
1364 struct task_struct *me = current;
1365
1366 arch_pick_mmap_layout(me->mm, &bprm->rlim_stack);
1367
1368 arch_setup_new_exec();
1369
1370 /* Set the new mm task size. We have to do that late because it may
1371 * depend on TIF_32BIT which is only updated in flush_thread() on
1372 * some architectures like powerpc
1373 */
1374 me->mm->task_size = TASK_SIZE;
1375 up_write(&me->signal->exec_update_lock);
1376 mutex_unlock(&me->signal->cred_guard_mutex);
1377
1378 /* The exec locks are dropped: release the old address space now. */
1379 if (bprm->old_mm) {
1380 exec_mm_put_old(bprm->old_mm);
1381 bprm->old_mm = NULL;
1382 }
1383}
1384EXPORT_SYMBOL(setup_new_exec);
1385
1386/* Runs immediately before start_thread() takes over. */
1387void finalize_exec(struct linux_binprm *bprm)
1388{
1389 /* Store any stack rlimit changes before starting thread. */
1390 task_lock(current->group_leader);
1391 current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack;
1392 task_unlock(current->group_leader);
1393}
1394EXPORT_SYMBOL(finalize_exec);
1395
1396/*
1397 * Prepare credentials and lock ->cred_guard_mutex.
1398 * setup_new_exec() commits the new creds and drops the lock.
1399 * Or, if exec fails before, free_bprm() should release ->cred
1400 * and unlock.
1401 */
1402static int prepare_bprm_creds(struct linux_binprm *bprm)
1403{
1404 if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1405 return -ERESTARTNOINTR;
1406
1407 bprm->cred = prepare_exec_creds();
1408 if (likely(bprm->cred))
1409 return 0;
1410
1411 mutex_unlock(&current->signal->cred_guard_mutex);
1412 return -ENOMEM;
1413}
1414
1415/* Matches do_open_execat() */
1416static void do_close_execat(struct file *file)
1417{
1418 if (!file)
1419 return;
1420 exe_file_allow_write_access(file);
1421 fput(file);
1422}
1423
1424/**
1425 * bprm_open_interpreter - open the interpreter the binary asks for
1426 * @bprm: binary that is being executed
1427 * @path: the interpreter path named in the binary's PT_INTERP
1428 *
1429 * A binfmt_misc loader entry substitutes for the interpreter the binary
1430 * names. Hand out the stashed substitute if there is one and open @path
1431 * if there is not. The caller owns the reference either way and releases
1432 * it like any other open_exec() one.
1433 *
1434 * Return: the interpreter on success, an ERR_PTR on failure
1435 */
1436struct file *bprm_open_interpreter(struct linux_binprm *bprm, const char *path)
1437{
1438 if (bprm->loader)
1439 return no_free_ptr(bprm->loader);
1440 return open_exec(path);
1441}
1442
1443/**
1444 * bprm_drop_loader - discard a PT_INTERP substitute that does not apply
1445 * @bprm: binary that is being executed
1446 *
1447 * A binary without PT_INTERP has nothing to substitute for, so drop the
1448 * override and let the binary load natively rather than have
1449 * begin_new_exec() refuse it. A no-op once bprm_open_interpreter() took
1450 * the substitute.
1451 */
1452void bprm_drop_loader(struct linux_binprm *bprm)
1453{
1454 do_close_execat(no_free_ptr(bprm->loader));
1455}
1456
1457static void free_bprm(struct linux_binprm *bprm)
1458{
1459 if (bprm->mm) {
1460 acct_arg_size(bprm, 0);
1461 mmput(bprm->mm);
1462 }
1463 if (bprm->user_ns)
1464 put_user_ns(bprm->user_ns);
1465 free_arg_pages(bprm);
1466 if (bprm->cred) {
1467 /* in case exec fails before de_thread() succeeds */
1468 current->fs->in_exec = 0;
1469 mutex_unlock(&current->signal->cred_guard_mutex);
1470 abort_creds(bprm->cred);
1471 }
1472 /* exec swapped the mm but failed before setup_new_exec() freed it */
1473 if (bprm->old_mm)
1474 exec_mm_put_old(bprm->old_mm);
1475 do_close_execat(bprm->file);
1476 /* An unconsumed PT_INTERP substitute from a binfmt_misc loader entry. */
1477 bprm_drop_loader(bprm);
1478 do_close_execat(bprm->executable);
1479 /* If a binfmt changed the interp, free it. */
1480 if (bprm->interp != bprm->filename)
1481 kfree(bprm->interp);
1482 kfree(bprm->bpf_interp);
1483 if (bprm->bpf_interp_file)
1484 fput(bprm->bpf_interp_file);
1485 kfree(bprm->bpf_interp_arg);
1486 kfree(bprm->fdpath);
1487 kfree(bprm);
1488}
1489
1490static struct linux_binprm *alloc_bprm(int fd, struct filename *filename, int flags)
1491{
1492 struct linux_binprm *bprm;
1493 struct file *file;
1494 int retval = -ENOMEM;
1495
1496 file = do_open_execat(fd, filename, flags);
1497 if (IS_ERR(file))
1498 return ERR_CAST(file);
1499
1500 bprm = kzalloc_obj(*bprm);
1501 if (!bprm) {
1502 do_close_execat(file);
1503 return ERR_PTR(-ENOMEM);
1504 }
1505
1506 bprm->file = file;
1507
1508 if (fd == AT_FDCWD || filename->name[0] == '/') {
1509 bprm->filename = filename->name;
1510 } else {
1511 if (filename->name[0] == '\0') {
1512 bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd);
1513 bprm->comm_from_dentry = 1;
1514 } else {
1515 bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s",
1516 fd, filename->name);
1517 }
1518 if (!bprm->fdpath)
1519 goto out_free;
1520
1521 /*
1522 * Record that a name derived from an O_CLOEXEC fd will be
1523 * inaccessible after exec. This allows the code in exec to
1524 * choose to fail when the executable is not mmaped into the
1525 * interpreter and an open file descriptor is not passed to
1526 * the interpreter. This makes for a better user experience
1527 * than having the interpreter start and then immediately fail
1528 * when it finds the executable is inaccessible.
1529 */
1530 if (get_close_on_exec(fd))
1531 bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1532
1533 bprm->filename = bprm->fdpath;
1534 }
1535 bprm->interp = bprm->filename;
1536
1537 /*
1538 * At this point, security_file_open() has already been called (with
1539 * __FMODE_EXEC) and access control checks for AT_EXECVE_CHECK will
1540 * stop just after the security_bprm_creds_for_exec() call in
1541 * bprm_execve(). Indeed, the kernel should not try to parse the
1542 * content of the file with exec_binprm() nor change the calling
1543 * thread, which means that the following security functions will not
1544 * be called:
1545 * - security_bprm_check()
1546 * - security_bprm_creds_from_file()
1547 * - security_bprm_committing_creds()
1548 * - security_bprm_committed_creds()
1549 */
1550 bprm->is_check = !!(flags & AT_EXECVE_CHECK);
1551
1552 retval = bprm_mm_init(bprm);
1553 if (!retval)
1554 return bprm;
1555
1556out_free:
1557 free_bprm(bprm);
1558 return ERR_PTR(retval);
1559}
1560
1561DEFINE_CLASS(bprm, struct linux_binprm *, if (!IS_ERR(_T)) free_bprm(_T),
1562 alloc_bprm(fd, name, flags), int fd, struct filename *name, int flags)
1563
1564int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
1565{
1566 /* If a binfmt changed the interp, free it first. */
1567 if (bprm->interp != bprm->filename)
1568 kfree(bprm->interp);
1569 bprm->interp = kstrdup(interp, GFP_KERNEL);
1570 if (!bprm->interp)
1571 return -ENOMEM;
1572 return 0;
1573}
1574EXPORT_SYMBOL(bprm_change_interp);
1575
1576/*
1577 * determine how safe it is to execute the proposed program
1578 * - the caller must hold ->cred_guard_mutex to protect against
1579 * PTRACE_ATTACH or seccomp thread-sync
1580 */
1581static void check_unsafe_exec(struct linux_binprm *bprm)
1582{
1583 struct task_struct *p = current, *t;
1584 unsigned n_fs;
1585
1586 if (p->ptrace)
1587 bprm->unsafe |= LSM_UNSAFE_PTRACE;
1588
1589 /*
1590 * This isn't strictly necessary, but it makes it harder for LSMs to
1591 * mess up.
1592 */
1593 if (task_no_new_privs(current))
1594 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1595
1596 /*
1597 * If another task is sharing our fs, we cannot safely
1598 * suid exec because the differently privileged task
1599 * will be able to manipulate the current directory, etc.
1600 * It would be nice to force an unshare instead...
1601 *
1602 * Otherwise we set fs->in_exec = 1 to deny clone(CLONE_FS)
1603 * from another sub-thread until de_thread() succeeds, this
1604 * state is protected by cred_guard_mutex we hold.
1605 */
1606 n_fs = 1;
1607 read_seqlock_excl(&p->fs->seq);
1608 rcu_read_lock();
1609 for_other_threads(p, t) {
1610 if (t->fs == p->fs)
1611 n_fs++;
1612 }
1613 rcu_read_unlock();
1614
1615 /* "users" and "in_exec" locked for copy_fs() */
1616 if (p->fs->users > n_fs)
1617 bprm->unsafe |= LSM_UNSAFE_SHARE;
1618 else
1619 p->fs->in_exec = 1;
1620 read_sequnlock_excl(&p->fs->seq);
1621}
1622
1623static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
1624{
1625 /* Handle suid and sgid on files */
1626 struct mnt_idmap *idmap;
1627 struct inode *inode = file_inode(file);
1628 unsigned int mode;
1629 vfsuid_t vfsuid;
1630 vfsgid_t vfsgid;
1631 int err;
1632
1633 if (!mnt_may_suid(file->f_path.mnt))
1634 return;
1635
1636 if (task_no_new_privs(current))
1637 return;
1638
1639 mode = READ_ONCE(inode->i_mode);
1640 if (!(mode & (S_ISUID|S_ISGID)))
1641 return;
1642
1643 idmap = file_mnt_idmap(file);
1644
1645 /* Be careful if suid/sgid is set */
1646 inode_lock(inode);
1647
1648 /* Atomically reload and check mode/uid/gid now that lock held. */
1649 mode = inode->i_mode;
1650 vfsuid = i_uid_into_vfsuid(idmap, inode);
1651 vfsgid = i_gid_into_vfsgid(idmap, inode);
1652 err = inode_permission(idmap, inode, MAY_EXEC);
1653 inode_unlock(inode);
1654
1655 /* Did the exec bit vanish out from under us? Give up. */
1656 if (err)
1657 return;
1658
1659 /* We ignore suid/sgid if there are no mappings for them in the ns */
1660 if (!vfsuid_has_mapping(bprm->cred->user_ns, vfsuid) ||
1661 !vfsgid_has_mapping(bprm->cred->user_ns, vfsgid))
1662 return;
1663
1664 if (mode & S_ISUID) {
1665 bprm->per_clear |= PER_CLEAR_ON_SETID;
1666 bprm->cred->euid = vfsuid_into_kuid(vfsuid);
1667 }
1668
1669 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1670 bprm->per_clear |= PER_CLEAR_ON_SETID;
1671 bprm->cred->egid = vfsgid_into_kgid(vfsgid);
1672 }
1673}
1674
1675/*
1676 * Compute brpm->cred based upon the final binary.
1677 */
1678static int bprm_creds_from_file(struct linux_binprm *bprm)
1679{
1680 /* Compute creds based on which file? */
1681 struct file *file = bprm->execfd_creds ? bprm->executable : bprm->file;
1682
1683 bprm_fill_uid(bprm, file);
1684 return security_bprm_creds_from_file(bprm, file);
1685}
1686
1687/*
1688 * Fill the binprm structure from the inode.
1689 * Read the first BINPRM_BUF_SIZE bytes
1690 *
1691 * This may be called multiple times for binary chains (scripts for example).
1692 */
1693static int prepare_binprm(struct linux_binprm *bprm)
1694{
1695 loff_t pos = 0;
1696
1697 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1698 return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
1699}
1700
1701/*
1702 * Arguments are '\0' separated strings found at the location bprm->p
1703 * points to; chop off the first by relocating brpm->p to right after
1704 * the first '\0' encountered.
1705 */
1706int remove_arg_zero(struct linux_binprm *bprm)
1707{
1708 unsigned long offset;
1709 char *kaddr;
1710 struct page *page;
1711
1712 if (!bprm->argc)
1713 return 0;
1714
1715 do {
1716 offset = bprm->p & ~PAGE_MASK;
1717 page = get_arg_page(bprm, bprm->p, 0);
1718 if (!page)
1719 return -EFAULT;
1720 kaddr = kmap_local_page(page);
1721
1722 for (; offset < PAGE_SIZE && kaddr[offset];
1723 offset++, bprm->p++)
1724 ;
1725
1726 kunmap_local(kaddr);
1727 put_arg_page(page);
1728 } while (offset == PAGE_SIZE);
1729
1730 bprm->p++;
1731 bprm->argc--;
1732
1733 return 0;
1734}
1735EXPORT_SYMBOL(remove_arg_zero);
1736
1737/*
1738 * cycle the list of binary formats handler, until one recognizes the image
1739 */
1740static int search_binary_handler(struct linux_binprm *bprm)
1741{
1742 struct linux_binfmt *fmt;
1743 int retval;
1744
1745 retval = prepare_binprm(bprm);
1746 if (retval < 0)
1747 return retval;
1748
1749 retval = security_bprm_check(bprm);
1750 if (retval)
1751 return retval;
1752
1753 read_lock(&binfmt_lock);
1754 list_for_each_entry(fmt, &formats, lh) {
1755 if (!try_module_get(fmt->module))
1756 continue;
1757 read_unlock(&binfmt_lock);
1758
1759 retval = fmt->load_binary(bprm);
1760
1761 read_lock(&binfmt_lock);
1762 put_binfmt(fmt);
1763 if (bprm->point_of_no_return || (retval != -ENOEXEC)) {
1764 read_unlock(&binfmt_lock);
1765 return retval;
1766 }
1767 }
1768 read_unlock(&binfmt_lock);
1769
1770 return -ENOEXEC;
1771}
1772
1773/* binfmt handlers will call back into begin_new_exec() on success. */
1774static int exec_binprm(struct linux_binprm *bprm)
1775{
1776 pid_t old_pid, old_vpid;
1777 int ret, depth;
1778
1779 /* Need to fetch pid before load_binary changes it */
1780 old_pid = current->pid;
1781 rcu_read_lock();
1782 old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1783 rcu_read_unlock();
1784
1785 /* This allows 5 levels of binfmt rewrites before failing hard. */
1786 for (depth = 0;; depth++) {
1787 struct file *exec;
1788 if (depth > 5)
1789 return -ELOOP;
1790
1791 ret = search_binary_handler(bprm);
1792 if (ret < 0)
1793 return ret;
1794 if (!bprm->interpreter)
1795 break;
1796
1797 /* A stashed PT_INTERP substitute belonged to the replaced file. */
1798 bprm_drop_loader(bprm);
1799
1800 exec = bprm->file;
1801 bprm->file = bprm->interpreter;
1802 bprm->interpreter = NULL;
1803
1804 if (unlikely(bprm->have_execfd)) {
1805 if (bprm->executable) {
1806 do_close_execat(exec);
1807 return -ENOEXEC;
1808 }
1809 /* Kept for AT_EXECFD; the write denial rides along until hand-over. */
1810 bprm->executable = exec;
1811 } else {
1812 do_close_execat(exec);
1813 }
1814 }
1815
1816 audit_bprm(bprm);
1817 trace_sched_process_exec(current, old_pid, bprm);
1818 ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1819 proc_exec_connector(current);
1820 return 0;
1821}
1822
1823static int bprm_execve(struct linux_binprm *bprm)
1824{
1825 int retval;
1826
1827 retval = prepare_bprm_creds(bprm);
1828 if (retval)
1829 return retval;
1830
1831 /*
1832 * Check for unsafe execution states before exec_binprm(), which
1833 * will call back into begin_new_exec(), into bprm_creds_from_file(),
1834 * where setuid-ness is evaluated.
1835 */
1836 check_unsafe_exec(bprm);
1837 current->in_execve = 1;
1838 sched_mm_cid_before_execve(current);
1839
1840 sched_exec();
1841
1842 /* Set the unchanging part of bprm->cred */
1843 retval = security_bprm_creds_for_exec(bprm);
1844 if (retval || bprm->is_check)
1845 goto out;
1846
1847 retval = exec_binprm(bprm);
1848 if (retval < 0)
1849 goto out;
1850
1851 sched_mm_cid_after_execve(current);
1852 rseq_execve(current);
1853 /* execve succeeded */
1854 current->in_execve = 0;
1855 user_events_execve(current);
1856 acct_update_integrals(current);
1857 task_numa_free(current, false);
1858 return retval;
1859
1860out:
1861 /*
1862 * If past the point of no return ensure the code never
1863 * returns to the userspace process. Use an existing fatal
1864 * signal if present otherwise terminate the process with
1865 * SIGSEGV.
1866 */
1867 if (bprm->point_of_no_return && !fatal_signal_pending(current))
1868 force_fatal_sig(SIGSEGV);
1869
1870 sched_mm_cid_after_execve(current);
1871 rseq_force_update();
1872 current->in_execve = 0;
1873
1874 return retval;
1875}
1876
1877static int do_execveat_common(int fd, struct filename *filename,
1878 struct user_arg_ptr argv,
1879 struct user_arg_ptr envp,
1880 int flags)
1881{
1882 int retval;
1883
1884 /*
1885 * We move the actual failure in case of RLIMIT_NPROC excess from
1886 * set*uid() to execve() because too many poorly written programs
1887 * don't check setuid() return code. Here we additionally recheck
1888 * whether NPROC limit is still exceeded.
1889 */
1890 if ((current->flags & PF_NPROC_EXCEEDED) &&
1891 is_rlimit_overlimit(current_ucounts(), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC)))
1892 return -EAGAIN;
1893
1894 /* We're below the limit (still or again), so we don't want to make
1895 * further execve() calls fail. */
1896 current->flags &= ~PF_NPROC_EXCEEDED;
1897
1898 CLASS(bprm, bprm)(fd, filename, flags);
1899 if (IS_ERR(bprm))
1900 return PTR_ERR(bprm);
1901
1902 retval = count(argv, MAX_ARG_STRINGS);
1903 if (retval < 0)
1904 return retval;
1905 bprm->argc = retval;
1906
1907 retval = count(envp, MAX_ARG_STRINGS);
1908 if (retval < 0)
1909 return retval;
1910 bprm->envc = retval;
1911
1912 retval = bprm_stack_limits(bprm);
1913 if (retval < 0)
1914 return retval;
1915
1916 retval = copy_string_kernel(bprm->filename, bprm);
1917 if (retval < 0)
1918 return retval;
1919 bprm->exec = bprm->p;
1920
1921 retval = copy_strings(bprm->envc, envp, bprm);
1922 if (retval < 0)
1923 return retval;
1924
1925 retval = copy_strings(bprm->argc, argv, bprm);
1926 if (retval < 0)
1927 return retval;
1928
1929 /*
1930 * When argv is empty, add an empty string ("") as argv[0] to
1931 * ensure confused userspace programs that start processing
1932 * from argv[1] won't end up walking envp. See also
1933 * bprm_stack_limits().
1934 */
1935 if (bprm->argc == 0) {
1936 retval = copy_string_kernel("", bprm);
1937 if (retval < 0)
1938 return retval;
1939 bprm->argc = 1;
1940
1941 pr_warn_once("process '%s' launched '%s' with NULL argv: empty string added\n",
1942 current->comm, bprm->filename);
1943 }
1944
1945 return bprm_execve(bprm);
1946}
1947
1948int kernel_execve(const char *kernel_filename,
1949 const char *const *argv, const char *const *envp)
1950{
1951 int retval;
1952
1953 /* It is non-sense for kernel threads to call execve */
1954 if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
1955 return -EINVAL;
1956
1957 CLASS(filename_kernel, filename)(kernel_filename);
1958 CLASS(bprm, bprm)(AT_FDCWD, filename, 0);
1959 if (IS_ERR(bprm))
1960 return PTR_ERR(bprm);
1961
1962 retval = count_strings_kernel(argv);
1963 if (WARN_ON_ONCE(retval == 0))
1964 return -EINVAL;
1965 if (retval < 0)
1966 return retval;
1967 bprm->argc = retval;
1968
1969 retval = count_strings_kernel(envp);
1970 if (retval < 0)
1971 return retval;
1972 bprm->envc = retval;
1973
1974 retval = bprm_stack_limits(bprm);
1975 if (retval < 0)
1976 return retval;
1977
1978 retval = copy_string_kernel(bprm->filename, bprm);
1979 if (retval < 0)
1980 return retval;
1981 bprm->exec = bprm->p;
1982
1983 retval = copy_strings_kernel(bprm->envc, envp, bprm);
1984 if (retval < 0)
1985 return retval;
1986
1987 retval = copy_strings_kernel(bprm->argc, argv, bprm);
1988 if (retval < 0)
1989 return retval;
1990
1991 return bprm_execve(bprm);
1992}
1993
1994void set_binfmt(struct linux_binfmt *new)
1995{
1996 struct mm_struct *mm = current->mm;
1997
1998 if (mm->binfmt)
1999 module_put(mm->binfmt->module);
2000
2001 mm->binfmt = new;
2002 if (new)
2003 __module_get(new->module);
2004}
2005EXPORT_SYMBOL(set_binfmt);
2006
2007static inline struct user_arg_ptr native_arg(const char __user *const __user *p)
2008{
2009 return (struct user_arg_ptr){.ptr.native = p};
2010}
2011
2012SYSCALL_DEFINE3(execve,
2013 const char __user *, filename,
2014 const char __user *const __user *, argv,
2015 const char __user *const __user *, envp)
2016{
2017 CLASS(filename, name)(filename);
2018 return do_execveat_common(AT_FDCWD, name,
2019 native_arg(argv), native_arg(envp), 0);
2020}
2021
2022SYSCALL_DEFINE5(execveat,
2023 int, fd, const char __user *, filename,
2024 const char __user *const __user *, argv,
2025 const char __user *const __user *, envp,
2026 int, flags)
2027{
2028 CLASS(filename_uflags, name)(filename, flags);
2029 return do_execveat_common(fd, name,
2030 native_arg(argv), native_arg(envp), flags);
2031}
2032
2033#ifdef CONFIG_COMPAT
2034
2035static inline struct user_arg_ptr compat_arg(const compat_uptr_t __user *p)
2036{
2037 return (struct user_arg_ptr){.is_compat = true, .ptr.compat = p};
2038}
2039
2040COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
2041 const compat_uptr_t __user *, argv,
2042 const compat_uptr_t __user *, envp)
2043{
2044 CLASS(filename, name)(filename);
2045 return do_execveat_common(AT_FDCWD, name,
2046 compat_arg(argv), compat_arg(envp), 0);
2047}
2048
2049COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
2050 const char __user *, filename,
2051 const compat_uptr_t __user *, argv,
2052 const compat_uptr_t __user *, envp,
2053 int, flags)
2054{
2055 CLASS(filename_uflags, name)(filename, flags);
2056 return do_execveat_common(fd, name,
2057 compat_arg(argv), compat_arg(envp), flags);
2058}
2059#endif
2060
2061#ifdef CONFIG_SYSCTL
2062
2063static int proc_dointvec_minmax_coredump(const struct ctl_table *table, int write,
2064 void *buffer, size_t *lenp, loff_t *ppos)
2065{
2066 int error, old = READ_ONCE(suid_dumpable);
2067
2068 error = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
2069
2070 if (!error && write && (old != READ_ONCE(suid_dumpable)))
2071 validate_coredump_safety();
2072 return error;
2073}
2074
2075static const struct ctl_table fs_exec_sysctls[] = {
2076 {
2077 .procname = "suid_dumpable",
2078 .data = &suid_dumpable,
2079 .maxlen = sizeof(int),
2080 .mode = 0644,
2081 .proc_handler = proc_dointvec_minmax_coredump,
2082 .extra1 = SYSCTL_ZERO,
2083 .extra2 = SYSCTL_TWO,
2084 },
2085};
2086
2087static int __init init_fs_exec_sysctls(void)
2088{
2089 register_sysctl_init("fs", fs_exec_sysctls);
2090 return 0;
2091}
2092
2093fs_initcall(init_fs_exec_sysctls);
2094#endif /* CONFIG_SYSCTL */
2095
2096#ifdef CONFIG_EXEC_KUNIT_TEST
2097#include "tests/exec_kunit.c"
2098#endif