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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/signal.h>
39#include <linux/sched/numa_balancing.h>
40#include <linux/sched/task.h>
41#include <linux/pagemap.h>
42#include <linux/perf_event.h>
43#include <linux/highmem.h>
44#include <linux/spinlock.h>
45#include <linux/key.h>
46#include <linux/personality.h>
47#include <linux/binfmts.h>
48#include <linux/utsname.h>
49#include <linux/pid_namespace.h>
50#include <linux/module.h>
51#include <linux/namei.h>
52#include <linux/mount.h>
53#include <linux/security.h>
54#include <linux/syscalls.h>
55#include <linux/tsacct_kern.h>
56#include <linux/cn_proc.h>
57#include <linux/audit.h>
58#include <linux/kmod.h>
59#include <linux/fsnotify.h>
60#include <linux/fs_struct.h>
61#include <linux/oom.h>
62#include <linux/compat.h>
63#include <linux/vmalloc.h>
64#include <linux/io_uring.h>
65#include <linux/syscall_user_dispatch.h>
66#include <linux/coredump.h>
67#include <linux/time_namespace.h>
68#include <linux/user_events.h>
69#include <linux/rseq.h>
70#include <linux/ksm.h>
71
72#include <linux/uaccess.h>
73#include <asm/mmu_context.h>
74#include <asm/tlb.h>
75
76#include <trace/events/task.h>
77#include "internal.h"
78
79#include <trace/events/sched.h>
80
81static int bprm_creds_from_file(struct linux_binprm *bprm);
82
83int suid_dumpable = 0;
84
85static LIST_HEAD(formats);
86static DEFINE_RWLOCK(binfmt_lock);
87
88void __register_binfmt(struct linux_binfmt * fmt, int insert)
89{
90 write_lock(&binfmt_lock);
91 insert ? list_add(&fmt->lh, &formats) :
92 list_add_tail(&fmt->lh, &formats);
93 write_unlock(&binfmt_lock);
94}
95
96EXPORT_SYMBOL(__register_binfmt);
97
98void unregister_binfmt(struct linux_binfmt * fmt)
99{
100 write_lock(&binfmt_lock);
101 list_del(&fmt->lh);
102 write_unlock(&binfmt_lock);
103}
104
105EXPORT_SYMBOL(unregister_binfmt);
106
107static inline void put_binfmt(struct linux_binfmt * fmt)
108{
109 module_put(fmt->module);
110}
111
112bool path_noexec(const struct path *path)
113{
114 return (path->mnt->mnt_flags & MNT_NOEXEC) ||
115 (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
116}
117
118#ifdef CONFIG_USELIB
119/*
120 * Note that a shared library must be both readable and executable due to
121 * security reasons.
122 *
123 * Also note that we take the address to load from the file itself.
124 */
125SYSCALL_DEFINE1(uselib, const char __user *, library)
126{
127 struct linux_binfmt *fmt;
128 struct file *file;
129 struct filename *tmp = getname(library);
130 int error = PTR_ERR(tmp);
131 static const struct open_flags uselib_flags = {
132 .open_flag = O_LARGEFILE | O_RDONLY,
133 .acc_mode = MAY_READ | MAY_EXEC,
134 .intent = LOOKUP_OPEN,
135 .lookup_flags = LOOKUP_FOLLOW,
136 };
137
138 if (IS_ERR(tmp))
139 goto out;
140
141 file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
142 putname(tmp);
143 error = PTR_ERR(file);
144 if (IS_ERR(file))
145 goto out;
146
147 /*
148 * Check do_open_execat() for an explanation.
149 */
150 error = -EACCES;
151 if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode)) ||
152 path_noexec(&file->f_path))
153 goto exit;
154
155 error = -ENOEXEC;
156
157 read_lock(&binfmt_lock);
158 list_for_each_entry(fmt, &formats, lh) {
159 if (!fmt->load_shlib)
160 continue;
161 if (!try_module_get(fmt->module))
162 continue;
163 read_unlock(&binfmt_lock);
164 error = fmt->load_shlib(file);
165 read_lock(&binfmt_lock);
166 put_binfmt(fmt);
167 if (error != -ENOEXEC)
168 break;
169 }
170 read_unlock(&binfmt_lock);
171exit:
172 fput(file);
173out:
174 return error;
175}
176#endif /* #ifdef CONFIG_USELIB */
177
178#ifdef CONFIG_MMU
179/*
180 * The nascent bprm->mm is not visible until exec_mmap() but it can
181 * use a lot of memory, account these pages in current->mm temporary
182 * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
183 * change the counter back via acct_arg_size(0).
184 */
185static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
186{
187 struct mm_struct *mm = current->mm;
188 long diff = (long)(pages - bprm->vma_pages);
189
190 if (!mm || !diff)
191 return;
192
193 bprm->vma_pages = pages;
194 add_mm_counter(mm, MM_ANONPAGES, diff);
195}
196
197static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
198 int write)
199{
200 struct page *page;
201 struct vm_area_struct *vma = bprm->vma;
202 struct mm_struct *mm = bprm->mm;
203 int ret;
204
205 /*
206 * Avoid relying on expanding the stack down in GUP (which
207 * does not work for STACK_GROWSUP anyway), and just do it
208 * by hand ahead of time.
209 */
210 if (write && pos < vma->vm_start) {
211 mmap_write_lock(mm);
212 ret = expand_downwards(vma, pos);
213 if (unlikely(ret < 0)) {
214 mmap_write_unlock(mm);
215 return NULL;
216 }
217 mmap_write_downgrade(mm);
218 } else
219 mmap_read_lock(mm);
220
221 /*
222 * We are doing an exec(). 'current' is the process
223 * doing the exec and 'mm' is the new process's mm.
224 */
225 ret = get_user_pages_remote(mm, pos, 1,
226 write ? FOLL_WRITE : 0,
227 &page, NULL);
228 mmap_read_unlock(mm);
229 if (ret <= 0)
230 return NULL;
231
232 if (write)
233 acct_arg_size(bprm, vma_pages(vma));
234
235 return page;
236}
237
238static void put_arg_page(struct page *page)
239{
240 put_page(page);
241}
242
243static void free_arg_pages(struct linux_binprm *bprm)
244{
245}
246
247static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
248 struct page *page)
249{
250 flush_cache_page(bprm->vma, pos, page_to_pfn(page));
251}
252
253static int __bprm_mm_init(struct linux_binprm *bprm)
254{
255 int err;
256 struct vm_area_struct *vma = NULL;
257 struct mm_struct *mm = bprm->mm;
258
259 bprm->vma = vma = vm_area_alloc(mm);
260 if (!vma)
261 return -ENOMEM;
262 vma_set_anonymous(vma);
263
264 if (mmap_write_lock_killable(mm)) {
265 err = -EINTR;
266 goto err_free;
267 }
268
269 /*
270 * Need to be called with mmap write lock
271 * held, to avoid race with ksmd.
272 */
273 err = ksm_execve(mm);
274 if (err)
275 goto err_ksm;
276
277 /*
278 * Place the stack at the largest stack address the architecture
279 * supports. Later, we'll move this to an appropriate place. We don't
280 * use STACK_TOP because that can depend on attributes which aren't
281 * configured yet.
282 */
283 BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
284 vma->vm_end = STACK_TOP_MAX;
285 vma->vm_start = vma->vm_end - PAGE_SIZE;
286 vm_flags_init(vma, VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP);
287 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
288
289 err = insert_vm_struct(mm, vma);
290 if (err)
291 goto err;
292
293 mm->stack_vm = mm->total_vm = 1;
294 mmap_write_unlock(mm);
295 bprm->p = vma->vm_end - sizeof(void *);
296 return 0;
297err:
298 ksm_exit(mm);
299err_ksm:
300 mmap_write_unlock(mm);
301err_free:
302 bprm->vma = NULL;
303 vm_area_free(vma);
304 return err;
305}
306
307static bool valid_arg_len(struct linux_binprm *bprm, long len)
308{
309 return len <= MAX_ARG_STRLEN;
310}
311
312#else
313
314static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
315{
316}
317
318static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
319 int write)
320{
321 struct page *page;
322
323 page = bprm->page[pos / PAGE_SIZE];
324 if (!page && write) {
325 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
326 if (!page)
327 return NULL;
328 bprm->page[pos / PAGE_SIZE] = page;
329 }
330
331 return page;
332}
333
334static void put_arg_page(struct page *page)
335{
336}
337
338static void free_arg_page(struct linux_binprm *bprm, int i)
339{
340 if (bprm->page[i]) {
341 __free_page(bprm->page[i]);
342 bprm->page[i] = NULL;
343 }
344}
345
346static void free_arg_pages(struct linux_binprm *bprm)
347{
348 int i;
349
350 for (i = 0; i < MAX_ARG_PAGES; i++)
351 free_arg_page(bprm, i);
352}
353
354static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
355 struct page *page)
356{
357}
358
359static int __bprm_mm_init(struct linux_binprm *bprm)
360{
361 bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
362 return 0;
363}
364
365static bool valid_arg_len(struct linux_binprm *bprm, long len)
366{
367 return len <= bprm->p;
368}
369
370#endif /* CONFIG_MMU */
371
372/*
373 * Create a new mm_struct and populate it with a temporary stack
374 * vm_area_struct. We don't have enough context at this point to set the stack
375 * flags, permissions, and offset, so we use temporary values. We'll update
376 * them later in setup_arg_pages().
377 */
378static int bprm_mm_init(struct linux_binprm *bprm)
379{
380 int err;
381 struct mm_struct *mm = NULL;
382
383 bprm->mm = mm = mm_alloc();
384 err = -ENOMEM;
385 if (!mm)
386 goto err;
387
388 /* Save current stack limit for all calculations made during exec. */
389 task_lock(current->group_leader);
390 bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK];
391 task_unlock(current->group_leader);
392
393 err = __bprm_mm_init(bprm);
394 if (err)
395 goto err;
396
397 return 0;
398
399err:
400 if (mm) {
401 bprm->mm = NULL;
402 mmdrop(mm);
403 }
404
405 return err;
406}
407
408struct user_arg_ptr {
409#ifdef CONFIG_COMPAT
410 bool is_compat;
411#endif
412 union {
413 const char __user *const __user *native;
414#ifdef CONFIG_COMPAT
415 const compat_uptr_t __user *compat;
416#endif
417 } ptr;
418};
419
420static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
421{
422 const char __user *native;
423
424#ifdef CONFIG_COMPAT
425 if (unlikely(argv.is_compat)) {
426 compat_uptr_t compat;
427
428 if (get_user(compat, argv.ptr.compat + nr))
429 return ERR_PTR(-EFAULT);
430
431 return compat_ptr(compat);
432 }
433#endif
434
435 if (get_user(native, argv.ptr.native + nr))
436 return ERR_PTR(-EFAULT);
437
438 return native;
439}
440
441/*
442 * count() counts the number of strings in array ARGV.
443 */
444static int count(struct user_arg_ptr argv, int max)
445{
446 int i = 0;
447
448 if (argv.ptr.native != NULL) {
449 for (;;) {
450 const char __user *p = get_user_arg_ptr(argv, i);
451
452 if (!p)
453 break;
454
455 if (IS_ERR(p))
456 return -EFAULT;
457
458 if (i >= max)
459 return -E2BIG;
460 ++i;
461
462 if (fatal_signal_pending(current))
463 return -ERESTARTNOHAND;
464 cond_resched();
465 }
466 }
467 return i;
468}
469
470static int count_strings_kernel(const char *const *argv)
471{
472 int i;
473
474 if (!argv)
475 return 0;
476
477 for (i = 0; argv[i]; ++i) {
478 if (i >= MAX_ARG_STRINGS)
479 return -E2BIG;
480 if (fatal_signal_pending(current))
481 return -ERESTARTNOHAND;
482 cond_resched();
483 }
484 return i;
485}
486
487static inline int bprm_set_stack_limit(struct linux_binprm *bprm,
488 unsigned long limit)
489{
490#ifdef CONFIG_MMU
491 /* Avoid a pathological bprm->p. */
492 if (bprm->p < limit)
493 return -E2BIG;
494 bprm->argmin = bprm->p - limit;
495#endif
496 return 0;
497}
498static inline bool bprm_hit_stack_limit(struct linux_binprm *bprm)
499{
500#ifdef CONFIG_MMU
501 return bprm->p < bprm->argmin;
502#else
503 return false;
504#endif
505}
506
507/*
508 * Calculate bprm->argmin from:
509 * - _STK_LIM
510 * - ARG_MAX
511 * - bprm->rlim_stack.rlim_cur
512 * - bprm->argc
513 * - bprm->envc
514 * - bprm->p
515 */
516static int bprm_stack_limits(struct linux_binprm *bprm)
517{
518 unsigned long limit, ptr_size;
519
520 /*
521 * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
522 * (whichever is smaller) for the argv+env strings.
523 * This ensures that:
524 * - the remaining binfmt code will not run out of stack space,
525 * - the program will have a reasonable amount of stack left
526 * to work from.
527 */
528 limit = _STK_LIM / 4 * 3;
529 limit = min(limit, bprm->rlim_stack.rlim_cur / 4);
530 /*
531 * We've historically supported up to 32 pages (ARG_MAX)
532 * of argument strings even with small stacks
533 */
534 limit = max_t(unsigned long, limit, ARG_MAX);
535 /* Reject totally pathological counts. */
536 if (bprm->argc < 0 || bprm->envc < 0)
537 return -E2BIG;
538 /*
539 * We must account for the size of all the argv and envp pointers to
540 * the argv and envp strings, since they will also take up space in
541 * the stack. They aren't stored until much later when we can't
542 * signal to the parent that the child has run out of stack space.
543 * Instead, calculate it here so it's possible to fail gracefully.
544 *
545 * In the case of argc = 0, make sure there is space for adding a
546 * empty string (which will bump argc to 1), to ensure confused
547 * userspace programs don't start processing from argv[1], thinking
548 * argc can never be 0, to keep them from walking envp by accident.
549 * See do_execveat_common().
550 */
551 if (check_add_overflow(max(bprm->argc, 1), bprm->envc, &ptr_size) ||
552 check_mul_overflow(ptr_size, sizeof(void *), &ptr_size))
553 return -E2BIG;
554 if (limit <= ptr_size)
555 return -E2BIG;
556 limit -= ptr_size;
557
558 return bprm_set_stack_limit(bprm, limit);
559}
560
561/*
562 * 'copy_strings()' copies argument/environment strings from the old
563 * processes's memory to the new process's stack. The call to get_user_pages()
564 * ensures the destination page is created and not swapped out.
565 */
566static int copy_strings(int argc, struct user_arg_ptr argv,
567 struct linux_binprm *bprm)
568{
569 struct page *kmapped_page = NULL;
570 char *kaddr = NULL;
571 unsigned long kpos = 0;
572 int ret;
573
574 while (argc-- > 0) {
575 const char __user *str;
576 int len;
577 unsigned long pos;
578
579 ret = -EFAULT;
580 str = get_user_arg_ptr(argv, argc);
581 if (IS_ERR(str))
582 goto out;
583
584 len = strnlen_user(str, MAX_ARG_STRLEN);
585 if (!len)
586 goto out;
587
588 ret = -E2BIG;
589 if (!valid_arg_len(bprm, len))
590 goto out;
591
592 /* We're going to work our way backwards. */
593 pos = bprm->p;
594 str += len;
595 bprm->p -= len;
596 if (bprm_hit_stack_limit(bprm))
597 goto out;
598
599 while (len > 0) {
600 int offset, bytes_to_copy;
601
602 if (fatal_signal_pending(current)) {
603 ret = -ERESTARTNOHAND;
604 goto out;
605 }
606 cond_resched();
607
608 offset = pos % PAGE_SIZE;
609 if (offset == 0)
610 offset = PAGE_SIZE;
611
612 bytes_to_copy = offset;
613 if (bytes_to_copy > len)
614 bytes_to_copy = len;
615
616 offset -= bytes_to_copy;
617 pos -= bytes_to_copy;
618 str -= bytes_to_copy;
619 len -= bytes_to_copy;
620
621 if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
622 struct page *page;
623
624 page = get_arg_page(bprm, pos, 1);
625 if (!page) {
626 ret = -E2BIG;
627 goto out;
628 }
629
630 if (kmapped_page) {
631 flush_dcache_page(kmapped_page);
632 kunmap_local(kaddr);
633 put_arg_page(kmapped_page);
634 }
635 kmapped_page = page;
636 kaddr = kmap_local_page(kmapped_page);
637 kpos = pos & PAGE_MASK;
638 flush_arg_page(bprm, kpos, kmapped_page);
639 }
640 if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
641 ret = -EFAULT;
642 goto out;
643 }
644 }
645 }
646 ret = 0;
647out:
648 if (kmapped_page) {
649 flush_dcache_page(kmapped_page);
650 kunmap_local(kaddr);
651 put_arg_page(kmapped_page);
652 }
653 return ret;
654}
655
656/*
657 * Copy and argument/environment string from the kernel to the processes stack.
658 */
659int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
660{
661 int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;
662 unsigned long pos = bprm->p;
663
664 if (len == 0)
665 return -EFAULT;
666 if (!valid_arg_len(bprm, len))
667 return -E2BIG;
668
669 /* We're going to work our way backwards. */
670 arg += len;
671 bprm->p -= len;
672 if (bprm_hit_stack_limit(bprm))
673 return -E2BIG;
674
675 while (len > 0) {
676 unsigned int bytes_to_copy = min_t(unsigned int, len,
677 min_not_zero(offset_in_page(pos), PAGE_SIZE));
678 struct page *page;
679
680 pos -= bytes_to_copy;
681 arg -= bytes_to_copy;
682 len -= bytes_to_copy;
683
684 page = get_arg_page(bprm, pos, 1);
685 if (!page)
686 return -E2BIG;
687 flush_arg_page(bprm, pos & PAGE_MASK, page);
688 memcpy_to_page(page, offset_in_page(pos), arg, bytes_to_copy);
689 put_arg_page(page);
690 }
691
692 return 0;
693}
694EXPORT_SYMBOL(copy_string_kernel);
695
696static int copy_strings_kernel(int argc, const char *const *argv,
697 struct linux_binprm *bprm)
698{
699 while (argc-- > 0) {
700 int ret = copy_string_kernel(argv[argc], bprm);
701 if (ret < 0)
702 return ret;
703 if (fatal_signal_pending(current))
704 return -ERESTARTNOHAND;
705 cond_resched();
706 }
707 return 0;
708}
709
710#ifdef CONFIG_MMU
711
712/*
713 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
714 * the stack is optionally relocated, and some extra space is added.
715 */
716int setup_arg_pages(struct linux_binprm *bprm,
717 unsigned long stack_top,
718 int executable_stack)
719{
720 unsigned long ret;
721 unsigned long stack_shift;
722 struct mm_struct *mm = current->mm;
723 struct vm_area_struct *vma = bprm->vma;
724 struct vm_area_struct *prev = NULL;
725 unsigned long vm_flags;
726 unsigned long stack_base;
727 unsigned long stack_size;
728 unsigned long stack_expand;
729 unsigned long rlim_stack;
730 struct mmu_gather tlb;
731 struct vma_iterator vmi;
732
733#ifdef CONFIG_STACK_GROWSUP
734 /* Limit stack size */
735 stack_base = bprm->rlim_stack.rlim_max;
736
737 stack_base = calc_max_stack_size(stack_base);
738
739 /* Add space for stack randomization. */
740 if (current->flags & PF_RANDOMIZE)
741 stack_base += (STACK_RND_MASK << PAGE_SHIFT);
742
743 /* Make sure we didn't let the argument array grow too large. */
744 if (vma->vm_end - vma->vm_start > stack_base)
745 return -ENOMEM;
746
747 stack_base = PAGE_ALIGN(stack_top - stack_base);
748
749 stack_shift = vma->vm_start - stack_base;
750 mm->arg_start = bprm->p - stack_shift;
751 bprm->p = vma->vm_end - stack_shift;
752#else
753 stack_top = arch_align_stack(stack_top);
754 stack_top = PAGE_ALIGN(stack_top);
755
756 if (unlikely(stack_top < mmap_min_addr) ||
757 unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
758 return -ENOMEM;
759
760 stack_shift = vma->vm_end - stack_top;
761
762 bprm->p -= stack_shift;
763 mm->arg_start = bprm->p;
764#endif
765
766 if (bprm->loader)
767 bprm->loader -= stack_shift;
768 bprm->exec -= stack_shift;
769
770 if (mmap_write_lock_killable(mm))
771 return -EINTR;
772
773 vm_flags = VM_STACK_FLAGS;
774
775 /*
776 * Adjust stack execute permissions; explicitly enable for
777 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
778 * (arch default) otherwise.
779 */
780 if (unlikely(executable_stack == EXSTACK_ENABLE_X))
781 vm_flags |= VM_EXEC;
782 else if (executable_stack == EXSTACK_DISABLE_X)
783 vm_flags &= ~VM_EXEC;
784 vm_flags |= mm->def_flags;
785 vm_flags |= VM_STACK_INCOMPLETE_SETUP;
786
787 vma_iter_init(&vmi, mm, vma->vm_start);
788
789 tlb_gather_mmu(&tlb, mm);
790 ret = mprotect_fixup(&vmi, &tlb, vma, &prev, vma->vm_start, vma->vm_end,
791 vm_flags);
792 tlb_finish_mmu(&tlb);
793
794 if (ret)
795 goto out_unlock;
796 BUG_ON(prev != vma);
797
798 if (unlikely(vm_flags & VM_EXEC)) {
799 pr_warn_once("process '%pD4' started with executable stack\n",
800 bprm->file);
801 }
802
803 /* Move stack pages down in memory. */
804 if (stack_shift) {
805 /*
806 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once
807 * the binfmt code determines where the new stack should reside, we shift it to
808 * its final location.
809 */
810 ret = relocate_vma_down(vma, stack_shift);
811 if (ret)
812 goto out_unlock;
813 }
814
815 /* mprotect_fixup is overkill to remove the temporary stack flags */
816 vm_flags_clear(vma, VM_STACK_INCOMPLETE_SETUP);
817
818 stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
819 stack_size = vma->vm_end - vma->vm_start;
820 /*
821 * Align this down to a page boundary as expand_stack
822 * will align it up.
823 */
824 rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK;
825
826 stack_expand = min(rlim_stack, stack_size + stack_expand);
827
828#ifdef CONFIG_STACK_GROWSUP
829 stack_base = vma->vm_start + stack_expand;
830#else
831 stack_base = vma->vm_end - stack_expand;
832#endif
833 current->mm->start_stack = bprm->p;
834 ret = expand_stack_locked(vma, stack_base);
835 if (ret)
836 ret = -EFAULT;
837
838out_unlock:
839 mmap_write_unlock(mm);
840 return ret;
841}
842EXPORT_SYMBOL(setup_arg_pages);
843
844#else
845
846/*
847 * Transfer the program arguments and environment from the holding pages
848 * onto the stack. The provided stack pointer is adjusted accordingly.
849 */
850int transfer_args_to_stack(struct linux_binprm *bprm,
851 unsigned long *sp_location)
852{
853 unsigned long index, stop, sp;
854 int ret = 0;
855
856 stop = bprm->p >> PAGE_SHIFT;
857 sp = *sp_location;
858
859 for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
860 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
861 char *src = kmap_local_page(bprm->page[index]) + offset;
862 sp -= PAGE_SIZE - offset;
863 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
864 ret = -EFAULT;
865 kunmap_local(src);
866 if (ret)
867 goto out;
868 }
869
870 bprm->exec += *sp_location - MAX_ARG_PAGES * PAGE_SIZE;
871 *sp_location = sp;
872
873out:
874 return ret;
875}
876EXPORT_SYMBOL(transfer_args_to_stack);
877
878#endif /* CONFIG_MMU */
879
880/*
881 * On success, caller must call do_close_execat() on the returned
882 * struct file to close it.
883 */
884static struct file *do_open_execat(int fd, struct filename *name, int flags)
885{
886 int err;
887 struct file *file __free(fput) = NULL;
888 struct open_flags open_exec_flags = {
889 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
890 .acc_mode = MAY_EXEC,
891 .intent = LOOKUP_OPEN,
892 .lookup_flags = LOOKUP_FOLLOW,
893 };
894
895 if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
896 return ERR_PTR(-EINVAL);
897 if (flags & AT_SYMLINK_NOFOLLOW)
898 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
899 if (flags & AT_EMPTY_PATH)
900 open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
901
902 file = do_filp_open(fd, name, &open_exec_flags);
903 if (IS_ERR(file))
904 return file;
905
906 /*
907 * In the past the regular type check was here. It moved to may_open() in
908 * 633fb6ac3980 ("exec: move S_ISREG() check earlier"). Since then it is
909 * an invariant that all non-regular files error out before we get here.
910 */
911 if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode)) ||
912 path_noexec(&file->f_path))
913 return ERR_PTR(-EACCES);
914
915 err = deny_write_access(file);
916 if (err)
917 return ERR_PTR(err);
918
919 return no_free_ptr(file);
920}
921
922/**
923 * open_exec - Open a path name for execution
924 *
925 * @name: path name to open with the intent of executing it.
926 *
927 * Returns ERR_PTR on failure or allocated struct file on success.
928 *
929 * As this is a wrapper for the internal do_open_execat(), callers
930 * must call allow_write_access() before fput() on release. Also see
931 * do_close_execat().
932 */
933struct file *open_exec(const char *name)
934{
935 struct filename *filename = getname_kernel(name);
936 struct file *f = ERR_CAST(filename);
937
938 if (!IS_ERR(filename)) {
939 f = do_open_execat(AT_FDCWD, filename, 0);
940 putname(filename);
941 }
942 return f;
943}
944EXPORT_SYMBOL(open_exec);
945
946#if defined(CONFIG_BINFMT_FLAT) || defined(CONFIG_BINFMT_ELF_FDPIC)
947ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
948{
949 ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
950 if (res > 0)
951 flush_icache_user_range(addr, addr + len);
952 return res;
953}
954EXPORT_SYMBOL(read_code);
955#endif
956
957/*
958 * Maps the mm_struct mm into the current task struct.
959 * On success, this function returns with exec_update_lock
960 * held for writing.
961 */
962static int exec_mmap(struct mm_struct *mm)
963{
964 struct task_struct *tsk;
965 struct mm_struct *old_mm, *active_mm;
966 int ret;
967
968 /* Notify parent that we're no longer interested in the old VM */
969 tsk = current;
970 old_mm = current->mm;
971 exec_mm_release(tsk, old_mm);
972
973 ret = down_write_killable(&tsk->signal->exec_update_lock);
974 if (ret)
975 return ret;
976
977 if (old_mm) {
978 /*
979 * If there is a pending fatal signal perhaps a signal
980 * whose default action is to create a coredump get
981 * out and die instead of going through with the exec.
982 */
983 ret = mmap_read_lock_killable(old_mm);
984 if (ret) {
985 up_write(&tsk->signal->exec_update_lock);
986 return ret;
987 }
988 }
989
990 task_lock(tsk);
991 membarrier_exec_mmap(mm);
992
993 local_irq_disable();
994 active_mm = tsk->active_mm;
995 tsk->active_mm = mm;
996 tsk->mm = mm;
997 mm_init_cid(mm, tsk);
998 /*
999 * This prevents preemption while active_mm is being loaded and
1000 * it and mm are being updated, which could cause problems for
1001 * lazy tlb mm refcounting when these are updated by context
1002 * switches. Not all architectures can handle irqs off over
1003 * activate_mm yet.
1004 */
1005 if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
1006 local_irq_enable();
1007 activate_mm(active_mm, mm);
1008 if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
1009 local_irq_enable();
1010 lru_gen_add_mm(mm);
1011 task_unlock(tsk);
1012 lru_gen_use_mm(mm);
1013 if (old_mm) {
1014 mmap_read_unlock(old_mm);
1015 BUG_ON(active_mm != old_mm);
1016 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
1017 mm_update_next_owner(old_mm);
1018 mmput(old_mm);
1019 return 0;
1020 }
1021 mmdrop_lazy_tlb(active_mm);
1022 return 0;
1023}
1024
1025static int de_thread(struct task_struct *tsk)
1026{
1027 struct signal_struct *sig = tsk->signal;
1028 struct sighand_struct *oldsighand = tsk->sighand;
1029 spinlock_t *lock = &oldsighand->siglock;
1030
1031 if (thread_group_empty(tsk))
1032 goto no_thread_group;
1033
1034 /*
1035 * Kill all other threads in the thread group.
1036 */
1037 spin_lock_irq(lock);
1038 if ((sig->flags & SIGNAL_GROUP_EXIT) || sig->group_exec_task) {
1039 /*
1040 * Another group action in progress, just
1041 * return so that the signal is processed.
1042 */
1043 spin_unlock_irq(lock);
1044 return -EAGAIN;
1045 }
1046
1047 sig->group_exec_task = tsk;
1048 sig->notify_count = zap_other_threads(tsk);
1049 if (!thread_group_leader(tsk))
1050 sig->notify_count--;
1051
1052 while (sig->notify_count) {
1053 __set_current_state(TASK_KILLABLE);
1054 spin_unlock_irq(lock);
1055 schedule();
1056 if (__fatal_signal_pending(tsk))
1057 goto killed;
1058 spin_lock_irq(lock);
1059 }
1060 spin_unlock_irq(lock);
1061
1062 /*
1063 * At this point all other threads have exited, all we have to
1064 * do is to wait for the thread group leader to become inactive,
1065 * and to assume its PID:
1066 */
1067 if (!thread_group_leader(tsk)) {
1068 struct task_struct *leader = tsk->group_leader;
1069
1070 for (;;) {
1071 cgroup_threadgroup_change_begin(tsk);
1072 write_lock_irq(&tasklist_lock);
1073 /*
1074 * Do this under tasklist_lock to ensure that
1075 * exit_notify() can't miss ->group_exec_task
1076 */
1077 sig->notify_count = -1;
1078 if (likely(leader->exit_state))
1079 break;
1080 __set_current_state(TASK_KILLABLE);
1081 write_unlock_irq(&tasklist_lock);
1082 cgroup_threadgroup_change_end(tsk);
1083 schedule();
1084 if (__fatal_signal_pending(tsk))
1085 goto killed;
1086 }
1087
1088 /*
1089 * The only record we have of the real-time age of a
1090 * process, regardless of execs it's done, is start_time.
1091 * All the past CPU time is accumulated in signal_struct
1092 * from sister threads now dead. But in this non-leader
1093 * exec, nothing survives from the original leader thread,
1094 * whose birth marks the true age of this process now.
1095 * When we take on its identity by switching to its PID, we
1096 * also take its birthdate (always earlier than our own).
1097 */
1098 tsk->start_time = leader->start_time;
1099 tsk->start_boottime = leader->start_boottime;
1100
1101 BUG_ON(!same_thread_group(leader, tsk));
1102 /*
1103 * An exec() starts a new thread group with the
1104 * TGID of the previous thread group. Rehash the
1105 * two threads with a switched PID, and release
1106 * the former thread group leader:
1107 */
1108
1109 /* Become a process group leader with the old leader's pid.
1110 * The old leader becomes a thread of the this thread group.
1111 */
1112 exchange_tids(tsk, leader);
1113 transfer_pid(leader, tsk, PIDTYPE_TGID);
1114 transfer_pid(leader, tsk, PIDTYPE_PGID);
1115 transfer_pid(leader, tsk, PIDTYPE_SID);
1116
1117 list_replace_rcu(&leader->tasks, &tsk->tasks);
1118 list_replace_init(&leader->sibling, &tsk->sibling);
1119
1120 tsk->group_leader = tsk;
1121 leader->group_leader = tsk;
1122
1123 tsk->exit_signal = SIGCHLD;
1124 leader->exit_signal = -1;
1125
1126 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1127 leader->exit_state = EXIT_DEAD;
1128 /*
1129 * We are going to release_task()->ptrace_unlink() silently,
1130 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1131 * the tracer won't block again waiting for this thread.
1132 */
1133 if (unlikely(leader->ptrace))
1134 __wake_up_parent(leader, leader->parent);
1135 write_unlock_irq(&tasklist_lock);
1136 cgroup_threadgroup_change_end(tsk);
1137
1138 release_task(leader);
1139 }
1140
1141 sig->group_exec_task = NULL;
1142 sig->notify_count = 0;
1143
1144no_thread_group:
1145 /* we have changed execution domain */
1146 tsk->exit_signal = SIGCHLD;
1147
1148 BUG_ON(!thread_group_leader(tsk));
1149 return 0;
1150
1151killed:
1152 /* protects against exit_notify() and __exit_signal() */
1153 read_lock(&tasklist_lock);
1154 sig->group_exec_task = NULL;
1155 sig->notify_count = 0;
1156 read_unlock(&tasklist_lock);
1157 return -EAGAIN;
1158}
1159
1160
1161/*
1162 * This function makes sure the current process has its own signal table,
1163 * so that flush_signal_handlers can later reset the handlers without
1164 * disturbing other processes. (Other processes might share the signal
1165 * table via the CLONE_SIGHAND option to clone().)
1166 */
1167static int unshare_sighand(struct task_struct *me)
1168{
1169 struct sighand_struct *oldsighand = me->sighand;
1170
1171 if (refcount_read(&oldsighand->count) != 1) {
1172 struct sighand_struct *newsighand;
1173 /*
1174 * This ->sighand is shared with the CLONE_SIGHAND
1175 * but not CLONE_THREAD task, switch to the new one.
1176 */
1177 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1178 if (!newsighand)
1179 return -ENOMEM;
1180
1181 refcount_set(&newsighand->count, 1);
1182
1183 write_lock_irq(&tasklist_lock);
1184 spin_lock(&oldsighand->siglock);
1185 memcpy(newsighand->action, oldsighand->action,
1186 sizeof(newsighand->action));
1187 rcu_assign_pointer(me->sighand, newsighand);
1188 spin_unlock(&oldsighand->siglock);
1189 write_unlock_irq(&tasklist_lock);
1190
1191 __cleanup_sighand(oldsighand);
1192 }
1193 return 0;
1194}
1195
1196/*
1197 * These functions flushes out all traces of the currently running executable
1198 * so that a new one can be started
1199 */
1200
1201void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1202{
1203 task_lock(tsk);
1204 trace_task_rename(tsk, buf);
1205 strscpy_pad(tsk->comm, buf, sizeof(tsk->comm));
1206 task_unlock(tsk);
1207 perf_event_comm(tsk, exec);
1208}
1209
1210/*
1211 * Calling this is the point of no return. None of the failures will be
1212 * seen by userspace since either the process is already taking a fatal
1213 * signal (via de_thread() or coredump), or will have SEGV raised
1214 * (after exec_mmap()) by search_binary_handler (see below).
1215 */
1216int begin_new_exec(struct linux_binprm * bprm)
1217{
1218 struct task_struct *me = current;
1219 int retval;
1220
1221 /* Once we are committed compute the creds */
1222 retval = bprm_creds_from_file(bprm);
1223 if (retval)
1224 return retval;
1225
1226 /*
1227 * This tracepoint marks the point before flushing the old exec where
1228 * the current task is still unchanged, but errors are fatal (point of
1229 * no return). The later "sched_process_exec" tracepoint is called after
1230 * the current task has successfully switched to the new exec.
1231 */
1232 trace_sched_prepare_exec(current, bprm);
1233
1234 /*
1235 * Ensure all future errors are fatal.
1236 */
1237 bprm->point_of_no_return = true;
1238
1239 /*
1240 * Make this the only thread in the thread group.
1241 */
1242 retval = de_thread(me);
1243 if (retval)
1244 goto out;
1245
1246 /*
1247 * Cancel any io_uring activity across execve
1248 */
1249 io_uring_task_cancel();
1250
1251 /* Ensure the files table is not shared. */
1252 retval = unshare_files();
1253 if (retval)
1254 goto out;
1255
1256 /*
1257 * Must be called _before_ exec_mmap() as bprm->mm is
1258 * not visible until then. Doing it here also ensures
1259 * we don't race against replace_mm_exe_file().
1260 */
1261 retval = set_mm_exe_file(bprm->mm, bprm->file);
1262 if (retval)
1263 goto out;
1264
1265 /* If the binary is not readable then enforce mm->dumpable=0 */
1266 would_dump(bprm, bprm->file);
1267 if (bprm->have_execfd)
1268 would_dump(bprm, bprm->executable);
1269
1270 /*
1271 * Release all of the old mmap stuff
1272 */
1273 acct_arg_size(bprm, 0);
1274 retval = exec_mmap(bprm->mm);
1275 if (retval)
1276 goto out;
1277
1278 bprm->mm = NULL;
1279
1280 retval = exec_task_namespaces();
1281 if (retval)
1282 goto out_unlock;
1283
1284#ifdef CONFIG_POSIX_TIMERS
1285 spin_lock_irq(&me->sighand->siglock);
1286 posix_cpu_timers_exit(me);
1287 spin_unlock_irq(&me->sighand->siglock);
1288 exit_itimers(me);
1289 flush_itimer_signals();
1290#endif
1291
1292 /*
1293 * Make the signal table private.
1294 */
1295 retval = unshare_sighand(me);
1296 if (retval)
1297 goto out_unlock;
1298
1299 me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC |
1300 PF_NOFREEZE | PF_NO_SETAFFINITY);
1301 flush_thread();
1302 me->personality &= ~bprm->per_clear;
1303
1304 clear_syscall_work_syscall_user_dispatch(me);
1305
1306 /*
1307 * We have to apply CLOEXEC before we change whether the process is
1308 * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1309 * trying to access the should-be-closed file descriptors of a process
1310 * undergoing exec(2).
1311 */
1312 do_close_on_exec(me->files);
1313
1314 if (bprm->secureexec) {
1315 /* Make sure parent cannot signal privileged process. */
1316 me->pdeath_signal = 0;
1317
1318 /*
1319 * For secureexec, reset the stack limit to sane default to
1320 * avoid bad behavior from the prior rlimits. This has to
1321 * happen before arch_pick_mmap_layout(), which examines
1322 * RLIMIT_STACK, but after the point of no return to avoid
1323 * needing to clean up the change on failure.
1324 */
1325 if (bprm->rlim_stack.rlim_cur > _STK_LIM)
1326 bprm->rlim_stack.rlim_cur = _STK_LIM;
1327 }
1328
1329 me->sas_ss_sp = me->sas_ss_size = 0;
1330
1331 /*
1332 * Figure out dumpability. Note that this checking only of current
1333 * is wrong, but userspace depends on it. This should be testing
1334 * bprm->secureexec instead.
1335 */
1336 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
1337 !(uid_eq(current_euid(), current_uid()) &&
1338 gid_eq(current_egid(), current_gid())))
1339 set_dumpable(current->mm, suid_dumpable);
1340 else
1341 set_dumpable(current->mm, SUID_DUMP_USER);
1342
1343 perf_event_exec();
1344
1345 /*
1346 * If the original filename was empty, alloc_bprm() made up a path
1347 * that will probably not be useful to admins running ps or similar.
1348 * Let's fix it up to be something reasonable.
1349 */
1350 if (bprm->comm_from_dentry) {
1351 /*
1352 * Hold RCU lock to keep the name from being freed behind our back.
1353 * Use acquire semantics to make sure the terminating NUL from
1354 * __d_alloc() is seen.
1355 *
1356 * Note, we're deliberately sloppy here. We don't need to care about
1357 * detecting a concurrent rename and just want a terminated name.
1358 */
1359 rcu_read_lock();
1360 __set_task_comm(me, smp_load_acquire(&bprm->file->f_path.dentry->d_name.name),
1361 true);
1362 rcu_read_unlock();
1363 } else {
1364 __set_task_comm(me, kbasename(bprm->filename), true);
1365 }
1366
1367 /* An exec changes our domain. We are no longer part of the thread
1368 group */
1369 WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1);
1370 flush_signal_handlers(me, 0);
1371
1372 retval = set_cred_ucounts(bprm->cred);
1373 if (retval < 0)
1374 goto out_unlock;
1375
1376 /*
1377 * install the new credentials for this executable
1378 */
1379 security_bprm_committing_creds(bprm);
1380
1381 commit_creds(bprm->cred);
1382 bprm->cred = NULL;
1383
1384 /*
1385 * Disable monitoring for regular users
1386 * when executing setuid binaries. Must
1387 * wait until new credentials are committed
1388 * by commit_creds() above
1389 */
1390 if (get_dumpable(me->mm) != SUID_DUMP_USER)
1391 perf_event_exit_task(me);
1392 /*
1393 * cred_guard_mutex must be held at least to this point to prevent
1394 * ptrace_attach() from altering our determination of the task's
1395 * credentials; any time after this it may be unlocked.
1396 */
1397 security_bprm_committed_creds(bprm);
1398
1399 /* Pass the opened binary to the interpreter. */
1400 if (bprm->have_execfd) {
1401 retval = get_unused_fd_flags(0);
1402 if (retval < 0)
1403 goto out_unlock;
1404 fd_install(retval, bprm->executable);
1405 bprm->executable = NULL;
1406 bprm->execfd = retval;
1407 }
1408 return 0;
1409
1410out_unlock:
1411 up_write(&me->signal->exec_update_lock);
1412 if (!bprm->cred)
1413 mutex_unlock(&me->signal->cred_guard_mutex);
1414
1415out:
1416 return retval;
1417}
1418EXPORT_SYMBOL(begin_new_exec);
1419
1420void would_dump(struct linux_binprm *bprm, struct file *file)
1421{
1422 struct inode *inode = file_inode(file);
1423 struct mnt_idmap *idmap = file_mnt_idmap(file);
1424 if (inode_permission(idmap, inode, MAY_READ) < 0) {
1425 struct user_namespace *old, *user_ns;
1426 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1427
1428 /* Ensure mm->user_ns contains the executable */
1429 user_ns = old = bprm->mm->user_ns;
1430 while ((user_ns != &init_user_ns) &&
1431 !privileged_wrt_inode_uidgid(user_ns, idmap, inode))
1432 user_ns = user_ns->parent;
1433
1434 if (old != user_ns) {
1435 bprm->mm->user_ns = get_user_ns(user_ns);
1436 put_user_ns(old);
1437 }
1438 }
1439}
1440EXPORT_SYMBOL(would_dump);
1441
1442void setup_new_exec(struct linux_binprm * bprm)
1443{
1444 /* Setup things that can depend upon the personality */
1445 struct task_struct *me = current;
1446
1447 arch_pick_mmap_layout(me->mm, &bprm->rlim_stack);
1448
1449 arch_setup_new_exec();
1450
1451 /* Set the new mm task size. We have to do that late because it may
1452 * depend on TIF_32BIT which is only updated in flush_thread() on
1453 * some architectures like powerpc
1454 */
1455 me->mm->task_size = TASK_SIZE;
1456 up_write(&me->signal->exec_update_lock);
1457 mutex_unlock(&me->signal->cred_guard_mutex);
1458}
1459EXPORT_SYMBOL(setup_new_exec);
1460
1461/* Runs immediately before start_thread() takes over. */
1462void finalize_exec(struct linux_binprm *bprm)
1463{
1464 /* Store any stack rlimit changes before starting thread. */
1465 task_lock(current->group_leader);
1466 current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack;
1467 task_unlock(current->group_leader);
1468}
1469EXPORT_SYMBOL(finalize_exec);
1470
1471/*
1472 * Prepare credentials and lock ->cred_guard_mutex.
1473 * setup_new_exec() commits the new creds and drops the lock.
1474 * Or, if exec fails before, free_bprm() should release ->cred
1475 * and unlock.
1476 */
1477static int prepare_bprm_creds(struct linux_binprm *bprm)
1478{
1479 if (mutex_lock_interruptible(¤t->signal->cred_guard_mutex))
1480 return -ERESTARTNOINTR;
1481
1482 bprm->cred = prepare_exec_creds();
1483 if (likely(bprm->cred))
1484 return 0;
1485
1486 mutex_unlock(¤t->signal->cred_guard_mutex);
1487 return -ENOMEM;
1488}
1489
1490/* Matches do_open_execat() */
1491static void do_close_execat(struct file *file)
1492{
1493 if (!file)
1494 return;
1495 allow_write_access(file);
1496 fput(file);
1497}
1498
1499static void free_bprm(struct linux_binprm *bprm)
1500{
1501 if (bprm->mm) {
1502 acct_arg_size(bprm, 0);
1503 mmput(bprm->mm);
1504 }
1505 free_arg_pages(bprm);
1506 if (bprm->cred) {
1507 mutex_unlock(¤t->signal->cred_guard_mutex);
1508 abort_creds(bprm->cred);
1509 }
1510 do_close_execat(bprm->file);
1511 if (bprm->executable)
1512 fput(bprm->executable);
1513 /* If a binfmt changed the interp, free it. */
1514 if (bprm->interp != bprm->filename)
1515 kfree(bprm->interp);
1516 kfree(bprm->fdpath);
1517 kfree(bprm);
1518}
1519
1520static struct linux_binprm *alloc_bprm(int fd, struct filename *filename, int flags)
1521{
1522 struct linux_binprm *bprm;
1523 struct file *file;
1524 int retval = -ENOMEM;
1525
1526 file = do_open_execat(fd, filename, flags);
1527 if (IS_ERR(file))
1528 return ERR_CAST(file);
1529
1530 bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1531 if (!bprm) {
1532 do_close_execat(file);
1533 return ERR_PTR(-ENOMEM);
1534 }
1535
1536 bprm->file = file;
1537
1538 if (fd == AT_FDCWD || filename->name[0] == '/') {
1539 bprm->filename = filename->name;
1540 } else {
1541 if (filename->name[0] == '\0') {
1542 bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd);
1543 bprm->comm_from_dentry = 1;
1544 } else {
1545 bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s",
1546 fd, filename->name);
1547 }
1548 if (!bprm->fdpath)
1549 goto out_free;
1550
1551 /*
1552 * Record that a name derived from an O_CLOEXEC fd will be
1553 * inaccessible after exec. This allows the code in exec to
1554 * choose to fail when the executable is not mmaped into the
1555 * interpreter and an open file descriptor is not passed to
1556 * the interpreter. This makes for a better user experience
1557 * than having the interpreter start and then immediately fail
1558 * when it finds the executable is inaccessible.
1559 */
1560 if (get_close_on_exec(fd))
1561 bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1562
1563 bprm->filename = bprm->fdpath;
1564 }
1565 bprm->interp = bprm->filename;
1566
1567 retval = bprm_mm_init(bprm);
1568 if (!retval)
1569 return bprm;
1570
1571out_free:
1572 free_bprm(bprm);
1573 return ERR_PTR(retval);
1574}
1575
1576int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
1577{
1578 /* If a binfmt changed the interp, free it first. */
1579 if (bprm->interp != bprm->filename)
1580 kfree(bprm->interp);
1581 bprm->interp = kstrdup(interp, GFP_KERNEL);
1582 if (!bprm->interp)
1583 return -ENOMEM;
1584 return 0;
1585}
1586EXPORT_SYMBOL(bprm_change_interp);
1587
1588/*
1589 * determine how safe it is to execute the proposed program
1590 * - the caller must hold ->cred_guard_mutex to protect against
1591 * PTRACE_ATTACH or seccomp thread-sync
1592 */
1593static void check_unsafe_exec(struct linux_binprm *bprm)
1594{
1595 struct task_struct *p = current, *t;
1596 unsigned n_fs;
1597
1598 if (p->ptrace)
1599 bprm->unsafe |= LSM_UNSAFE_PTRACE;
1600
1601 /*
1602 * This isn't strictly necessary, but it makes it harder for LSMs to
1603 * mess up.
1604 */
1605 if (task_no_new_privs(current))
1606 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1607
1608 /*
1609 * If another task is sharing our fs, we cannot safely
1610 * suid exec because the differently privileged task
1611 * will be able to manipulate the current directory, etc.
1612 * It would be nice to force an unshare instead...
1613 */
1614 n_fs = 1;
1615 spin_lock(&p->fs->lock);
1616 rcu_read_lock();
1617 for_other_threads(p, t) {
1618 if (t->fs == p->fs)
1619 n_fs++;
1620 }
1621 rcu_read_unlock();
1622
1623 /* "users" and "in_exec" locked for copy_fs() */
1624 if (p->fs->users > n_fs)
1625 bprm->unsafe |= LSM_UNSAFE_SHARE;
1626 else
1627 p->fs->in_exec = 1;
1628 spin_unlock(&p->fs->lock);
1629}
1630
1631static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
1632{
1633 /* Handle suid and sgid on files */
1634 struct mnt_idmap *idmap;
1635 struct inode *inode = file_inode(file);
1636 unsigned int mode;
1637 vfsuid_t vfsuid;
1638 vfsgid_t vfsgid;
1639 int err;
1640
1641 if (!mnt_may_suid(file->f_path.mnt))
1642 return;
1643
1644 if (task_no_new_privs(current))
1645 return;
1646
1647 mode = READ_ONCE(inode->i_mode);
1648 if (!(mode & (S_ISUID|S_ISGID)))
1649 return;
1650
1651 idmap = file_mnt_idmap(file);
1652
1653 /* Be careful if suid/sgid is set */
1654 inode_lock(inode);
1655
1656 /* Atomically reload and check mode/uid/gid now that lock held. */
1657 mode = inode->i_mode;
1658 vfsuid = i_uid_into_vfsuid(idmap, inode);
1659 vfsgid = i_gid_into_vfsgid(idmap, inode);
1660 err = inode_permission(idmap, inode, MAY_EXEC);
1661 inode_unlock(inode);
1662
1663 /* Did the exec bit vanish out from under us? Give up. */
1664 if (err)
1665 return;
1666
1667 /* We ignore suid/sgid if there are no mappings for them in the ns */
1668 if (!vfsuid_has_mapping(bprm->cred->user_ns, vfsuid) ||
1669 !vfsgid_has_mapping(bprm->cred->user_ns, vfsgid))
1670 return;
1671
1672 if (mode & S_ISUID) {
1673 bprm->per_clear |= PER_CLEAR_ON_SETID;
1674 bprm->cred->euid = vfsuid_into_kuid(vfsuid);
1675 }
1676
1677 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1678 bprm->per_clear |= PER_CLEAR_ON_SETID;
1679 bprm->cred->egid = vfsgid_into_kgid(vfsgid);
1680 }
1681}
1682
1683/*
1684 * Compute brpm->cred based upon the final binary.
1685 */
1686static int bprm_creds_from_file(struct linux_binprm *bprm)
1687{
1688 /* Compute creds based on which file? */
1689 struct file *file = bprm->execfd_creds ? bprm->executable : bprm->file;
1690
1691 bprm_fill_uid(bprm, file);
1692 return security_bprm_creds_from_file(bprm, file);
1693}
1694
1695/*
1696 * Fill the binprm structure from the inode.
1697 * Read the first BINPRM_BUF_SIZE bytes
1698 *
1699 * This may be called multiple times for binary chains (scripts for example).
1700 */
1701static int prepare_binprm(struct linux_binprm *bprm)
1702{
1703 loff_t pos = 0;
1704
1705 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1706 return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
1707}
1708
1709/*
1710 * Arguments are '\0' separated strings found at the location bprm->p
1711 * points to; chop off the first by relocating brpm->p to right after
1712 * the first '\0' encountered.
1713 */
1714int remove_arg_zero(struct linux_binprm *bprm)
1715{
1716 unsigned long offset;
1717 char *kaddr;
1718 struct page *page;
1719
1720 if (!bprm->argc)
1721 return 0;
1722
1723 do {
1724 offset = bprm->p & ~PAGE_MASK;
1725 page = get_arg_page(bprm, bprm->p, 0);
1726 if (!page)
1727 return -EFAULT;
1728 kaddr = kmap_local_page(page);
1729
1730 for (; offset < PAGE_SIZE && kaddr[offset];
1731 offset++, bprm->p++)
1732 ;
1733
1734 kunmap_local(kaddr);
1735 put_arg_page(page);
1736 } while (offset == PAGE_SIZE);
1737
1738 bprm->p++;
1739 bprm->argc--;
1740
1741 return 0;
1742}
1743EXPORT_SYMBOL(remove_arg_zero);
1744
1745#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1746/*
1747 * cycle the list of binary formats handler, until one recognizes the image
1748 */
1749static int search_binary_handler(struct linux_binprm *bprm)
1750{
1751 bool need_retry = IS_ENABLED(CONFIG_MODULES);
1752 struct linux_binfmt *fmt;
1753 int retval;
1754
1755 retval = prepare_binprm(bprm);
1756 if (retval < 0)
1757 return retval;
1758
1759 retval = security_bprm_check(bprm);
1760 if (retval)
1761 return retval;
1762
1763 retval = -ENOENT;
1764 retry:
1765 read_lock(&binfmt_lock);
1766 list_for_each_entry(fmt, &formats, lh) {
1767 if (!try_module_get(fmt->module))
1768 continue;
1769 read_unlock(&binfmt_lock);
1770
1771 retval = fmt->load_binary(bprm);
1772
1773 read_lock(&binfmt_lock);
1774 put_binfmt(fmt);
1775 if (bprm->point_of_no_return || (retval != -ENOEXEC)) {
1776 read_unlock(&binfmt_lock);
1777 return retval;
1778 }
1779 }
1780 read_unlock(&binfmt_lock);
1781
1782 if (need_retry) {
1783 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1784 printable(bprm->buf[2]) && printable(bprm->buf[3]))
1785 return retval;
1786 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1787 return retval;
1788 need_retry = false;
1789 goto retry;
1790 }
1791
1792 return retval;
1793}
1794
1795/* binfmt handlers will call back into begin_new_exec() on success. */
1796static int exec_binprm(struct linux_binprm *bprm)
1797{
1798 pid_t old_pid, old_vpid;
1799 int ret, depth;
1800
1801 /* Need to fetch pid before load_binary changes it */
1802 old_pid = current->pid;
1803 rcu_read_lock();
1804 old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1805 rcu_read_unlock();
1806
1807 /* This allows 4 levels of binfmt rewrites before failing hard. */
1808 for (depth = 0;; depth++) {
1809 struct file *exec;
1810 if (depth > 5)
1811 return -ELOOP;
1812
1813 ret = search_binary_handler(bprm);
1814 if (ret < 0)
1815 return ret;
1816 if (!bprm->interpreter)
1817 break;
1818
1819 exec = bprm->file;
1820 bprm->file = bprm->interpreter;
1821 bprm->interpreter = NULL;
1822
1823 allow_write_access(exec);
1824 if (unlikely(bprm->have_execfd)) {
1825 if (bprm->executable) {
1826 fput(exec);
1827 return -ENOEXEC;
1828 }
1829 bprm->executable = exec;
1830 } else
1831 fput(exec);
1832 }
1833
1834 audit_bprm(bprm);
1835 trace_sched_process_exec(current, old_pid, bprm);
1836 ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1837 proc_exec_connector(current);
1838 return 0;
1839}
1840
1841static int bprm_execve(struct linux_binprm *bprm)
1842{
1843 int retval;
1844
1845 retval = prepare_bprm_creds(bprm);
1846 if (retval)
1847 return retval;
1848
1849 /*
1850 * Check for unsafe execution states before exec_binprm(), which
1851 * will call back into begin_new_exec(), into bprm_creds_from_file(),
1852 * where setuid-ness is evaluated.
1853 */
1854 check_unsafe_exec(bprm);
1855 current->in_execve = 1;
1856 sched_mm_cid_before_execve(current);
1857
1858 sched_exec();
1859
1860 /* Set the unchanging part of bprm->cred */
1861 retval = security_bprm_creds_for_exec(bprm);
1862 if (retval)
1863 goto out;
1864
1865 retval = exec_binprm(bprm);
1866 if (retval < 0)
1867 goto out;
1868
1869 sched_mm_cid_after_execve(current);
1870 /* execve succeeded */
1871 current->fs->in_exec = 0;
1872 current->in_execve = 0;
1873 rseq_execve(current);
1874 user_events_execve(current);
1875 acct_update_integrals(current);
1876 task_numa_free(current, false);
1877 return retval;
1878
1879out:
1880 /*
1881 * If past the point of no return ensure the code never
1882 * returns to the userspace process. Use an existing fatal
1883 * signal if present otherwise terminate the process with
1884 * SIGSEGV.
1885 */
1886 if (bprm->point_of_no_return && !fatal_signal_pending(current))
1887 force_fatal_sig(SIGSEGV);
1888
1889 sched_mm_cid_after_execve(current);
1890 current->fs->in_exec = 0;
1891 current->in_execve = 0;
1892
1893 return retval;
1894}
1895
1896static int do_execveat_common(int fd, struct filename *filename,
1897 struct user_arg_ptr argv,
1898 struct user_arg_ptr envp,
1899 int flags)
1900{
1901 struct linux_binprm *bprm;
1902 int retval;
1903
1904 if (IS_ERR(filename))
1905 return PTR_ERR(filename);
1906
1907 /*
1908 * We move the actual failure in case of RLIMIT_NPROC excess from
1909 * set*uid() to execve() because too many poorly written programs
1910 * don't check setuid() return code. Here we additionally recheck
1911 * whether NPROC limit is still exceeded.
1912 */
1913 if ((current->flags & PF_NPROC_EXCEEDED) &&
1914 is_rlimit_overlimit(current_ucounts(), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
1915 retval = -EAGAIN;
1916 goto out_ret;
1917 }
1918
1919 /* We're below the limit (still or again), so we don't want to make
1920 * further execve() calls fail. */
1921 current->flags &= ~PF_NPROC_EXCEEDED;
1922
1923 bprm = alloc_bprm(fd, filename, flags);
1924 if (IS_ERR(bprm)) {
1925 retval = PTR_ERR(bprm);
1926 goto out_ret;
1927 }
1928
1929 retval = count(argv, MAX_ARG_STRINGS);
1930 if (retval == 0)
1931 pr_warn_once("process '%s' launched '%s' with NULL argv: empty string added\n",
1932 current->comm, bprm->filename);
1933 if (retval < 0)
1934 goto out_free;
1935 bprm->argc = retval;
1936
1937 retval = count(envp, MAX_ARG_STRINGS);
1938 if (retval < 0)
1939 goto out_free;
1940 bprm->envc = retval;
1941
1942 retval = bprm_stack_limits(bprm);
1943 if (retval < 0)
1944 goto out_free;
1945
1946 retval = copy_string_kernel(bprm->filename, bprm);
1947 if (retval < 0)
1948 goto out_free;
1949 bprm->exec = bprm->p;
1950
1951 retval = copy_strings(bprm->envc, envp, bprm);
1952 if (retval < 0)
1953 goto out_free;
1954
1955 retval = copy_strings(bprm->argc, argv, bprm);
1956 if (retval < 0)
1957 goto out_free;
1958
1959 /*
1960 * When argv is empty, add an empty string ("") as argv[0] to
1961 * ensure confused userspace programs that start processing
1962 * from argv[1] won't end up walking envp. See also
1963 * bprm_stack_limits().
1964 */
1965 if (bprm->argc == 0) {
1966 retval = copy_string_kernel("", bprm);
1967 if (retval < 0)
1968 goto out_free;
1969 bprm->argc = 1;
1970 }
1971
1972 retval = bprm_execve(bprm);
1973out_free:
1974 free_bprm(bprm);
1975
1976out_ret:
1977 putname(filename);
1978 return retval;
1979}
1980
1981int kernel_execve(const char *kernel_filename,
1982 const char *const *argv, const char *const *envp)
1983{
1984 struct filename *filename;
1985 struct linux_binprm *bprm;
1986 int fd = AT_FDCWD;
1987 int retval;
1988
1989 /* It is non-sense for kernel threads to call execve */
1990 if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
1991 return -EINVAL;
1992
1993 filename = getname_kernel(kernel_filename);
1994 if (IS_ERR(filename))
1995 return PTR_ERR(filename);
1996
1997 bprm = alloc_bprm(fd, filename, 0);
1998 if (IS_ERR(bprm)) {
1999 retval = PTR_ERR(bprm);
2000 goto out_ret;
2001 }
2002
2003 retval = count_strings_kernel(argv);
2004 if (WARN_ON_ONCE(retval == 0))
2005 retval = -EINVAL;
2006 if (retval < 0)
2007 goto out_free;
2008 bprm->argc = retval;
2009
2010 retval = count_strings_kernel(envp);
2011 if (retval < 0)
2012 goto out_free;
2013 bprm->envc = retval;
2014
2015 retval = bprm_stack_limits(bprm);
2016 if (retval < 0)
2017 goto out_free;
2018
2019 retval = copy_string_kernel(bprm->filename, bprm);
2020 if (retval < 0)
2021 goto out_free;
2022 bprm->exec = bprm->p;
2023
2024 retval = copy_strings_kernel(bprm->envc, envp, bprm);
2025 if (retval < 0)
2026 goto out_free;
2027
2028 retval = copy_strings_kernel(bprm->argc, argv, bprm);
2029 if (retval < 0)
2030 goto out_free;
2031
2032 retval = bprm_execve(bprm);
2033out_free:
2034 free_bprm(bprm);
2035out_ret:
2036 putname(filename);
2037 return retval;
2038}
2039
2040static int do_execve(struct filename *filename,
2041 const char __user *const __user *__argv,
2042 const char __user *const __user *__envp)
2043{
2044 struct user_arg_ptr argv = { .ptr.native = __argv };
2045 struct user_arg_ptr envp = { .ptr.native = __envp };
2046 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
2047}
2048
2049static int do_execveat(int fd, struct filename *filename,
2050 const char __user *const __user *__argv,
2051 const char __user *const __user *__envp,
2052 int flags)
2053{
2054 struct user_arg_ptr argv = { .ptr.native = __argv };
2055 struct user_arg_ptr envp = { .ptr.native = __envp };
2056
2057 return do_execveat_common(fd, filename, argv, envp, flags);
2058}
2059
2060#ifdef CONFIG_COMPAT
2061static int compat_do_execve(struct filename *filename,
2062 const compat_uptr_t __user *__argv,
2063 const compat_uptr_t __user *__envp)
2064{
2065 struct user_arg_ptr argv = {
2066 .is_compat = true,
2067 .ptr.compat = __argv,
2068 };
2069 struct user_arg_ptr envp = {
2070 .is_compat = true,
2071 .ptr.compat = __envp,
2072 };
2073 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
2074}
2075
2076static int compat_do_execveat(int fd, struct filename *filename,
2077 const compat_uptr_t __user *__argv,
2078 const compat_uptr_t __user *__envp,
2079 int flags)
2080{
2081 struct user_arg_ptr argv = {
2082 .is_compat = true,
2083 .ptr.compat = __argv,
2084 };
2085 struct user_arg_ptr envp = {
2086 .is_compat = true,
2087 .ptr.compat = __envp,
2088 };
2089 return do_execveat_common(fd, filename, argv, envp, flags);
2090}
2091#endif
2092
2093void set_binfmt(struct linux_binfmt *new)
2094{
2095 struct mm_struct *mm = current->mm;
2096
2097 if (mm->binfmt)
2098 module_put(mm->binfmt->module);
2099
2100 mm->binfmt = new;
2101 if (new)
2102 __module_get(new->module);
2103}
2104EXPORT_SYMBOL(set_binfmt);
2105
2106/*
2107 * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
2108 */
2109void set_dumpable(struct mm_struct *mm, int value)
2110{
2111 if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
2112 return;
2113
2114 set_mask_bits(&mm->flags, MMF_DUMPABLE_MASK, value);
2115}
2116
2117SYSCALL_DEFINE3(execve,
2118 const char __user *, filename,
2119 const char __user *const __user *, argv,
2120 const char __user *const __user *, envp)
2121{
2122 return do_execve(getname(filename), argv, envp);
2123}
2124
2125SYSCALL_DEFINE5(execveat,
2126 int, fd, const char __user *, filename,
2127 const char __user *const __user *, argv,
2128 const char __user *const __user *, envp,
2129 int, flags)
2130{
2131 return do_execveat(fd,
2132 getname_uflags(filename, flags),
2133 argv, envp, flags);
2134}
2135
2136#ifdef CONFIG_COMPAT
2137COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
2138 const compat_uptr_t __user *, argv,
2139 const compat_uptr_t __user *, envp)
2140{
2141 return compat_do_execve(getname(filename), argv, envp);
2142}
2143
2144COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
2145 const char __user *, filename,
2146 const compat_uptr_t __user *, argv,
2147 const compat_uptr_t __user *, envp,
2148 int, flags)
2149{
2150 return compat_do_execveat(fd,
2151 getname_uflags(filename, flags),
2152 argv, envp, flags);
2153}
2154#endif
2155
2156#ifdef CONFIG_SYSCTL
2157
2158static int proc_dointvec_minmax_coredump(const struct ctl_table *table, int write,
2159 void *buffer, size_t *lenp, loff_t *ppos)
2160{
2161 int error = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
2162
2163 if (!error)
2164 validate_coredump_safety();
2165 return error;
2166}
2167
2168static struct ctl_table fs_exec_sysctls[] = {
2169 {
2170 .procname = "suid_dumpable",
2171 .data = &suid_dumpable,
2172 .maxlen = sizeof(int),
2173 .mode = 0644,
2174 .proc_handler = proc_dointvec_minmax_coredump,
2175 .extra1 = SYSCTL_ZERO,
2176 .extra2 = SYSCTL_TWO,
2177 },
2178};
2179
2180static int __init init_fs_exec_sysctls(void)
2181{
2182 register_sysctl_init("fs", fs_exec_sysctls);
2183 return 0;
2184}
2185
2186fs_initcall(init_fs_exec_sysctls);
2187#endif /* CONFIG_SYSCTL */
2188
2189#ifdef CONFIG_EXEC_KUNIT_TEST
2190#include "tests/exec_kunit.c"
2191#endif