projects/linux·blob v5.11 · 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/vmacache.h>
32#include <linux/stat.h>
33#include <linux/fcntl.h>
34#include <linux/swap.h>
35#include <linux/string.h>
36#include <linux/init.h>
37#include <linux/sched/mm.h>
38#include <linux/sched/coredump.h>
39#include <linux/sched/signal.h>
40#include <linux/sched/numa_balancing.h>
41#include <linux/sched/task.h>
42#include <linux/pagemap.h>
43#include <linux/perf_event.h>
44#include <linux/highmem.h>
45#include <linux/spinlock.h>
46#include <linux/key.h>
47#include <linux/personality.h>
48#include <linux/binfmts.h>
49#include <linux/utsname.h>
50#include <linux/pid_namespace.h>
51#include <linux/module.h>
52#include <linux/namei.h>
53#include <linux/mount.h>
54#include <linux/security.h>
55#include <linux/syscalls.h>
56#include <linux/tsacct_kern.h>
57#include <linux/cn_proc.h>
58#include <linux/audit.h>
59#include <linux/tracehook.h>
60#include <linux/kmod.h>
61#include <linux/fsnotify.h>
62#include <linux/fs_struct.h>
63#include <linux/oom.h>
64#include <linux/compat.h>
65#include <linux/vmalloc.h>
66#include <linux/io_uring.h>
67#include <linux/syscall_user_dispatch.h>
68
69#include <linux/uaccess.h>
70#include <asm/mmu_context.h>
71#include <asm/tlb.h>
72
73#include <trace/events/task.h>
74#include "internal.h"
75
76#include <trace/events/sched.h>
77
78static int bprm_creds_from_file(struct linux_binprm *bprm);
79
80int suid_dumpable = 0;
81
82static LIST_HEAD(formats);
83static DEFINE_RWLOCK(binfmt_lock);
84
85void __register_binfmt(struct linux_binfmt * fmt, int insert)
86{
87 BUG_ON(!fmt);
88 if (WARN_ON(!fmt->load_binary))
89 return;
90 write_lock(&binfmt_lock);
91 insert ? list_add(&fmt->lh, &formats) :
92 list_add_tail(&fmt->lh, &formats);
93 write_unlock(&binfmt_lock);
94}
95
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 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 | __FMODE_EXEC,
133 .acc_mode = MAY_READ | MAY_EXEC,
134 .intent = LOOKUP_OPEN,
135 .lookup_flags = LOOKUP_FOLLOW,
136 };
137
138 if (IS_ERR(tmp))
139 goto out;
140
141 file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
142 putname(tmp);
143 error = PTR_ERR(file);
144 if (IS_ERR(file))
145 goto out;
146
147 /*
148 * may_open() has already checked for this, so it should be
149 * impossible to trip now. But we need to be extra cautious
150 * and check again at the very end too.
151 */
152 error = -EACCES;
153 if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
154 path_noexec(&file->f_path)))
155 goto exit;
156
157 fsnotify_open(file);
158
159 error = -ENOEXEC;
160
161 read_lock(&binfmt_lock);
162 list_for_each_entry(fmt, &formats, lh) {
163 if (!fmt->load_shlib)
164 continue;
165 if (!try_module_get(fmt->module))
166 continue;
167 read_unlock(&binfmt_lock);
168 error = fmt->load_shlib(file);
169 read_lock(&binfmt_lock);
170 put_binfmt(fmt);
171 if (error != -ENOEXEC)
172 break;
173 }
174 read_unlock(&binfmt_lock);
175exit:
176 fput(file);
177out:
178 return error;
179}
180#endif /* #ifdef CONFIG_USELIB */
181
182#ifdef CONFIG_MMU
183/*
184 * The nascent bprm->mm is not visible until exec_mmap() but it can
185 * use a lot of memory, account these pages in current->mm temporary
186 * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
187 * change the counter back via acct_arg_size(0).
188 */
189static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
190{
191 struct mm_struct *mm = current->mm;
192 long diff = (long)(pages - bprm->vma_pages);
193
194 if (!mm || !diff)
195 return;
196
197 bprm->vma_pages = pages;
198 add_mm_counter(mm, MM_ANONPAGES, diff);
199}
200
201static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
202 int write)
203{
204 struct page *page;
205 int ret;
206 unsigned int gup_flags = FOLL_FORCE;
207
208#ifdef CONFIG_STACK_GROWSUP
209 if (write) {
210 ret = expand_downwards(bprm->vma, pos);
211 if (ret < 0)
212 return NULL;
213 }
214#endif
215
216 if (write)
217 gup_flags |= FOLL_WRITE;
218
219 /*
220 * We are doing an exec(). 'current' is the process
221 * doing the exec and bprm->mm is the new process's mm.
222 */
223 ret = get_user_pages_remote(bprm->mm, pos, 1, gup_flags,
224 &page, NULL, NULL);
225 if (ret <= 0)
226 return NULL;
227
228 if (write)
229 acct_arg_size(bprm, vma_pages(bprm->vma));
230
231 return page;
232}
233
234static void put_arg_page(struct page *page)
235{
236 put_page(page);
237}
238
239static void free_arg_pages(struct linux_binprm *bprm)
240{
241}
242
243static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
244 struct page *page)
245{
246 flush_cache_page(bprm->vma, pos, page_to_pfn(page));
247}
248
249static int __bprm_mm_init(struct linux_binprm *bprm)
250{
251 int err;
252 struct vm_area_struct *vma = NULL;
253 struct mm_struct *mm = bprm->mm;
254
255 bprm->vma = vma = vm_area_alloc(mm);
256 if (!vma)
257 return -ENOMEM;
258 vma_set_anonymous(vma);
259
260 if (mmap_write_lock_killable(mm)) {
261 err = -EINTR;
262 goto err_free;
263 }
264
265 /*
266 * Place the stack at the largest stack address the architecture
267 * supports. Later, we'll move this to an appropriate place. We don't
268 * use STACK_TOP because that can depend on attributes which aren't
269 * configured yet.
270 */
271 BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
272 vma->vm_end = STACK_TOP_MAX;
273 vma->vm_start = vma->vm_end - PAGE_SIZE;
274 vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
275 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
276
277 err = insert_vm_struct(mm, vma);
278 if (err)
279 goto err;
280
281 mm->stack_vm = mm->total_vm = 1;
282 mmap_write_unlock(mm);
283 bprm->p = vma->vm_end - sizeof(void *);
284 return 0;
285err:
286 mmap_write_unlock(mm);
287err_free:
288 bprm->vma = NULL;
289 vm_area_free(vma);
290 return err;
291}
292
293static bool valid_arg_len(struct linux_binprm *bprm, long len)
294{
295 return len <= MAX_ARG_STRLEN;
296}
297
298#else
299
300static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
301{
302}
303
304static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
305 int write)
306{
307 struct page *page;
308
309 page = bprm->page[pos / PAGE_SIZE];
310 if (!page && write) {
311 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
312 if (!page)
313 return NULL;
314 bprm->page[pos / PAGE_SIZE] = page;
315 }
316
317 return page;
318}
319
320static void put_arg_page(struct page *page)
321{
322}
323
324static void free_arg_page(struct linux_binprm *bprm, int i)
325{
326 if (bprm->page[i]) {
327 __free_page(bprm->page[i]);
328 bprm->page[i] = NULL;
329 }
330}
331
332static void free_arg_pages(struct linux_binprm *bprm)
333{
334 int i;
335
336 for (i = 0; i < MAX_ARG_PAGES; i++)
337 free_arg_page(bprm, i);
338}
339
340static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
341 struct page *page)
342{
343}
344
345static int __bprm_mm_init(struct linux_binprm *bprm)
346{
347 bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
348 return 0;
349}
350
351static bool valid_arg_len(struct linux_binprm *bprm, long len)
352{
353 return len <= bprm->p;
354}
355
356#endif /* CONFIG_MMU */
357
358/*
359 * Create a new mm_struct and populate it with a temporary stack
360 * vm_area_struct. We don't have enough context at this point to set the stack
361 * flags, permissions, and offset, so we use temporary values. We'll update
362 * them later in setup_arg_pages().
363 */
364static int bprm_mm_init(struct linux_binprm *bprm)
365{
366 int err;
367 struct mm_struct *mm = NULL;
368
369 bprm->mm = mm = mm_alloc();
370 err = -ENOMEM;
371 if (!mm)
372 goto err;
373
374 /* Save current stack limit for all calculations made during exec. */
375 task_lock(current->group_leader);
376 bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK];
377 task_unlock(current->group_leader);
378
379 err = __bprm_mm_init(bprm);
380 if (err)
381 goto err;
382
383 return 0;
384
385err:
386 if (mm) {
387 bprm->mm = NULL;
388 mmdrop(mm);
389 }
390
391 return err;
392}
393
394struct user_arg_ptr {
395#ifdef CONFIG_COMPAT
396 bool is_compat;
397#endif
398 union {
399 const char __user *const __user *native;
400#ifdef CONFIG_COMPAT
401 const compat_uptr_t __user *compat;
402#endif
403 } ptr;
404};
405
406static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
407{
408 const char __user *native;
409
410#ifdef CONFIG_COMPAT
411 if (unlikely(argv.is_compat)) {
412 compat_uptr_t compat;
413
414 if (get_user(compat, argv.ptr.compat + nr))
415 return ERR_PTR(-EFAULT);
416
417 return compat_ptr(compat);
418 }
419#endif
420
421 if (get_user(native, argv.ptr.native + nr))
422 return ERR_PTR(-EFAULT);
423
424 return native;
425}
426
427/*
428 * count() counts the number of strings in array ARGV.
429 */
430static int count(struct user_arg_ptr argv, int max)
431{
432 int i = 0;
433
434 if (argv.ptr.native != NULL) {
435 for (;;) {
436 const char __user *p = get_user_arg_ptr(argv, i);
437
438 if (!p)
439 break;
440
441 if (IS_ERR(p))
442 return -EFAULT;
443
444 if (i >= max)
445 return -E2BIG;
446 ++i;
447
448 if (fatal_signal_pending(current))
449 return -ERESTARTNOHAND;
450 cond_resched();
451 }
452 }
453 return i;
454}
455
456static int count_strings_kernel(const char *const *argv)
457{
458 int i;
459
460 if (!argv)
461 return 0;
462
463 for (i = 0; argv[i]; ++i) {
464 if (i >= MAX_ARG_STRINGS)
465 return -E2BIG;
466 if (fatal_signal_pending(current))
467 return -ERESTARTNOHAND;
468 cond_resched();
469 }
470 return i;
471}
472
473static int bprm_stack_limits(struct linux_binprm *bprm)
474{
475 unsigned long limit, ptr_size;
476
477 /*
478 * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
479 * (whichever is smaller) for the argv+env strings.
480 * This ensures that:
481 * - the remaining binfmt code will not run out of stack space,
482 * - the program will have a reasonable amount of stack left
483 * to work from.
484 */
485 limit = _STK_LIM / 4 * 3;
486 limit = min(limit, bprm->rlim_stack.rlim_cur / 4);
487 /*
488 * We've historically supported up to 32 pages (ARG_MAX)
489 * of argument strings even with small stacks
490 */
491 limit = max_t(unsigned long, limit, ARG_MAX);
492 /*
493 * We must account for the size of all the argv and envp pointers to
494 * the argv and envp strings, since they will also take up space in
495 * the stack. They aren't stored until much later when we can't
496 * signal to the parent that the child has run out of stack space.
497 * Instead, calculate it here so it's possible to fail gracefully.
498 */
499 ptr_size = (bprm->argc + bprm->envc) * sizeof(void *);
500 if (limit <= ptr_size)
501 return -E2BIG;
502 limit -= ptr_size;
503
504 bprm->argmin = bprm->p - limit;
505 return 0;
506}
507
508/*
509 * 'copy_strings()' copies argument/environment strings from the old
510 * processes's memory to the new process's stack. The call to get_user_pages()
511 * ensures the destination page is created and not swapped out.
512 */
513static int copy_strings(int argc, struct user_arg_ptr argv,
514 struct linux_binprm *bprm)
515{
516 struct page *kmapped_page = NULL;
517 char *kaddr = NULL;
518 unsigned long kpos = 0;
519 int ret;
520
521 while (argc-- > 0) {
522 const char __user *str;
523 int len;
524 unsigned long pos;
525
526 ret = -EFAULT;
527 str = get_user_arg_ptr(argv, argc);
528 if (IS_ERR(str))
529 goto out;
530
531 len = strnlen_user(str, MAX_ARG_STRLEN);
532 if (!len)
533 goto out;
534
535 ret = -E2BIG;
536 if (!valid_arg_len(bprm, len))
537 goto out;
538
539 /* We're going to work our way backwords. */
540 pos = bprm->p;
541 str += len;
542 bprm->p -= len;
543#ifdef CONFIG_MMU
544 if (bprm->p < bprm->argmin)
545 goto out;
546#endif
547
548 while (len > 0) {
549 int offset, bytes_to_copy;
550
551 if (fatal_signal_pending(current)) {
552 ret = -ERESTARTNOHAND;
553 goto out;
554 }
555 cond_resched();
556
557 offset = pos % PAGE_SIZE;
558 if (offset == 0)
559 offset = PAGE_SIZE;
560
561 bytes_to_copy = offset;
562 if (bytes_to_copy > len)
563 bytes_to_copy = len;
564
565 offset -= bytes_to_copy;
566 pos -= bytes_to_copy;
567 str -= bytes_to_copy;
568 len -= bytes_to_copy;
569
570 if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
571 struct page *page;
572
573 page = get_arg_page(bprm, pos, 1);
574 if (!page) {
575 ret = -E2BIG;
576 goto out;
577 }
578
579 if (kmapped_page) {
580 flush_kernel_dcache_page(kmapped_page);
581 kunmap(kmapped_page);
582 put_arg_page(kmapped_page);
583 }
584 kmapped_page = page;
585 kaddr = kmap(kmapped_page);
586 kpos = pos & PAGE_MASK;
587 flush_arg_page(bprm, kpos, kmapped_page);
588 }
589 if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
590 ret = -EFAULT;
591 goto out;
592 }
593 }
594 }
595 ret = 0;
596out:
597 if (kmapped_page) {
598 flush_kernel_dcache_page(kmapped_page);
599 kunmap(kmapped_page);
600 put_arg_page(kmapped_page);
601 }
602 return ret;
603}
604
605/*
606 * Copy and argument/environment string from the kernel to the processes stack.
607 */
608int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
609{
610 int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;
611 unsigned long pos = bprm->p;
612
613 if (len == 0)
614 return -EFAULT;
615 if (!valid_arg_len(bprm, len))
616 return -E2BIG;
617
618 /* We're going to work our way backwards. */
619 arg += len;
620 bprm->p -= len;
621 if (IS_ENABLED(CONFIG_MMU) && bprm->p < bprm->argmin)
622 return -E2BIG;
623
624 while (len > 0) {
625 unsigned int bytes_to_copy = min_t(unsigned int, len,
626 min_not_zero(offset_in_page(pos), PAGE_SIZE));
627 struct page *page;
628 char *kaddr;
629
630 pos -= bytes_to_copy;
631 arg -= bytes_to_copy;
632 len -= bytes_to_copy;
633
634 page = get_arg_page(bprm, pos, 1);
635 if (!page)
636 return -E2BIG;
637 kaddr = kmap_atomic(page);
638 flush_arg_page(bprm, pos & PAGE_MASK, page);
639 memcpy(kaddr + offset_in_page(pos), arg, bytes_to_copy);
640 flush_kernel_dcache_page(page);
641 kunmap_atomic(kaddr);
642 put_arg_page(page);
643 }
644
645 return 0;
646}
647EXPORT_SYMBOL(copy_string_kernel);
648
649static int copy_strings_kernel(int argc, const char *const *argv,
650 struct linux_binprm *bprm)
651{
652 while (argc-- > 0) {
653 int ret = copy_string_kernel(argv[argc], bprm);
654 if (ret < 0)
655 return ret;
656 if (fatal_signal_pending(current))
657 return -ERESTARTNOHAND;
658 cond_resched();
659 }
660 return 0;
661}
662
663#ifdef CONFIG_MMU
664
665/*
666 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once
667 * the binfmt code determines where the new stack should reside, we shift it to
668 * its final location. The process proceeds as follows:
669 *
670 * 1) Use shift to calculate the new vma endpoints.
671 * 2) Extend vma to cover both the old and new ranges. This ensures the
672 * arguments passed to subsequent functions are consistent.
673 * 3) Move vma's page tables to the new range.
674 * 4) Free up any cleared pgd range.
675 * 5) Shrink the vma to cover only the new range.
676 */
677static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
678{
679 struct mm_struct *mm = vma->vm_mm;
680 unsigned long old_start = vma->vm_start;
681 unsigned long old_end = vma->vm_end;
682 unsigned long length = old_end - old_start;
683 unsigned long new_start = old_start - shift;
684 unsigned long new_end = old_end - shift;
685 struct mmu_gather tlb;
686
687 BUG_ON(new_start > new_end);
688
689 /*
690 * ensure there are no vmas between where we want to go
691 * and where we are
692 */
693 if (vma != find_vma(mm, new_start))
694 return -EFAULT;
695
696 /*
697 * cover the whole range: [new_start, old_end)
698 */
699 if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
700 return -ENOMEM;
701
702 /*
703 * move the page tables downwards, on failure we rely on
704 * process cleanup to remove whatever mess we made.
705 */
706 if (length != move_page_tables(vma, old_start,
707 vma, new_start, length, false))
708 return -ENOMEM;
709
710 lru_add_drain();
711 tlb_gather_mmu(&tlb, mm, old_start, old_end);
712 if (new_end > old_start) {
713 /*
714 * when the old and new regions overlap clear from new_end.
715 */
716 free_pgd_range(&tlb, new_end, old_end, new_end,
717 vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
718 } else {
719 /*
720 * otherwise, clean from old_start; this is done to not touch
721 * the address space in [new_end, old_start) some architectures
722 * have constraints on va-space that make this illegal (IA64) -
723 * for the others its just a little faster.
724 */
725 free_pgd_range(&tlb, old_start, old_end, new_end,
726 vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
727 }
728 tlb_finish_mmu(&tlb, old_start, old_end);
729
730 /*
731 * Shrink the vma to just the new range. Always succeeds.
732 */
733 vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
734
735 return 0;
736}
737
738/*
739 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
740 * the stack is optionally relocated, and some extra space is added.
741 */
742int setup_arg_pages(struct linux_binprm *bprm,
743 unsigned long stack_top,
744 int executable_stack)
745{
746 unsigned long ret;
747 unsigned long stack_shift;
748 struct mm_struct *mm = current->mm;
749 struct vm_area_struct *vma = bprm->vma;
750 struct vm_area_struct *prev = NULL;
751 unsigned long vm_flags;
752 unsigned long stack_base;
753 unsigned long stack_size;
754 unsigned long stack_expand;
755 unsigned long rlim_stack;
756
757#ifdef CONFIG_STACK_GROWSUP
758 /* Limit stack size */
759 stack_base = bprm->rlim_stack.rlim_max;
760
761 stack_base = calc_max_stack_size(stack_base);
762
763 /* Add space for stack randomization. */
764 stack_base += (STACK_RND_MASK << PAGE_SHIFT);
765
766 /* Make sure we didn't let the argument array grow too large. */
767 if (vma->vm_end - vma->vm_start > stack_base)
768 return -ENOMEM;
769
770 stack_base = PAGE_ALIGN(stack_top - stack_base);
771
772 stack_shift = vma->vm_start - stack_base;
773 mm->arg_start = bprm->p - stack_shift;
774 bprm->p = vma->vm_end - stack_shift;
775#else
776 stack_top = arch_align_stack(stack_top);
777 stack_top = PAGE_ALIGN(stack_top);
778
779 if (unlikely(stack_top < mmap_min_addr) ||
780 unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
781 return -ENOMEM;
782
783 stack_shift = vma->vm_end - stack_top;
784
785 bprm->p -= stack_shift;
786 mm->arg_start = bprm->p;
787#endif
788
789 if (bprm->loader)
790 bprm->loader -= stack_shift;
791 bprm->exec -= stack_shift;
792
793 if (mmap_write_lock_killable(mm))
794 return -EINTR;
795
796 vm_flags = VM_STACK_FLAGS;
797
798 /*
799 * Adjust stack execute permissions; explicitly enable for
800 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
801 * (arch default) otherwise.
802 */
803 if (unlikely(executable_stack == EXSTACK_ENABLE_X))
804 vm_flags |= VM_EXEC;
805 else if (executable_stack == EXSTACK_DISABLE_X)
806 vm_flags &= ~VM_EXEC;
807 vm_flags |= mm->def_flags;
808 vm_flags |= VM_STACK_INCOMPLETE_SETUP;
809
810 ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
811 vm_flags);
812 if (ret)
813 goto out_unlock;
814 BUG_ON(prev != vma);
815
816 if (unlikely(vm_flags & VM_EXEC)) {
817 pr_warn_once("process '%pD4' started with executable stack\n",
818 bprm->file);
819 }
820
821 /* Move stack pages down in memory. */
822 if (stack_shift) {
823 ret = shift_arg_pages(vma, stack_shift);
824 if (ret)
825 goto out_unlock;
826 }
827
828 /* mprotect_fixup is overkill to remove the temporary stack flags */
829 vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
830
831 stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
832 stack_size = vma->vm_end - vma->vm_start;
833 /*
834 * Align this down to a page boundary as expand_stack
835 * will align it up.
836 */
837 rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK;
838#ifdef CONFIG_STACK_GROWSUP
839 if (stack_size + stack_expand > rlim_stack)
840 stack_base = vma->vm_start + rlim_stack;
841 else
842 stack_base = vma->vm_end + stack_expand;
843#else
844 if (stack_size + stack_expand > rlim_stack)
845 stack_base = vma->vm_end - rlim_stack;
846 else
847 stack_base = vma->vm_start - stack_expand;
848#endif
849 current->mm->start_stack = bprm->p;
850 ret = expand_stack(vma, stack_base);
851 if (ret)
852 ret = -EFAULT;
853
854out_unlock:
855 mmap_write_unlock(mm);
856 return ret;
857}
858EXPORT_SYMBOL(setup_arg_pages);
859
860#else
861
862/*
863 * Transfer the program arguments and environment from the holding pages
864 * onto the stack. The provided stack pointer is adjusted accordingly.
865 */
866int transfer_args_to_stack(struct linux_binprm *bprm,
867 unsigned long *sp_location)
868{
869 unsigned long index, stop, sp;
870 int ret = 0;
871
872 stop = bprm->p >> PAGE_SHIFT;
873 sp = *sp_location;
874
875 for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
876 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
877 char *src = kmap(bprm->page[index]) + offset;
878 sp -= PAGE_SIZE - offset;
879 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
880 ret = -EFAULT;
881 kunmap(bprm->page[index]);
882 if (ret)
883 goto out;
884 }
885
886 *sp_location = sp;
887
888out:
889 return ret;
890}
891EXPORT_SYMBOL(transfer_args_to_stack);
892
893#endif /* CONFIG_MMU */
894
895static struct file *do_open_execat(int fd, struct filename *name, int flags)
896{
897 struct file *file;
898 int err;
899 struct open_flags open_exec_flags = {
900 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
901 .acc_mode = MAY_EXEC,
902 .intent = LOOKUP_OPEN,
903 .lookup_flags = LOOKUP_FOLLOW,
904 };
905
906 if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
907 return ERR_PTR(-EINVAL);
908 if (flags & AT_SYMLINK_NOFOLLOW)
909 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
910 if (flags & AT_EMPTY_PATH)
911 open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
912
913 file = do_filp_open(fd, name, &open_exec_flags);
914 if (IS_ERR(file))
915 goto out;
916
917 /*
918 * may_open() has already checked for this, so it should be
919 * impossible to trip now. But we need to be extra cautious
920 * and check again at the very end too.
921 */
922 err = -EACCES;
923 if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
924 path_noexec(&file->f_path)))
925 goto exit;
926
927 err = deny_write_access(file);
928 if (err)
929 goto exit;
930
931 if (name->name[0] != '\0')
932 fsnotify_open(file);
933
934out:
935 return file;
936
937exit:
938 fput(file);
939 return ERR_PTR(err);
940}
941
942struct file *open_exec(const char *name)
943{
944 struct filename *filename = getname_kernel(name);
945 struct file *f = ERR_CAST(filename);
946
947 if (!IS_ERR(filename)) {
948 f = do_open_execat(AT_FDCWD, filename, 0);
949 putname(filename);
950 }
951 return f;
952}
953EXPORT_SYMBOL(open_exec);
954
955#if defined(CONFIG_HAVE_AOUT) || defined(CONFIG_BINFMT_FLAT) || \
956 defined(CONFIG_BINFMT_ELF_FDPIC)
957ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
958{
959 ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
960 if (res > 0)
961 flush_icache_user_range(addr, addr + len);
962 return res;
963}
964EXPORT_SYMBOL(read_code);
965#endif
966
967/*
968 * Maps the mm_struct mm into the current task struct.
969 * On success, this function returns with exec_update_lock
970 * held for writing.
971 */
972static int exec_mmap(struct mm_struct *mm)
973{
974 struct task_struct *tsk;
975 struct mm_struct *old_mm, *active_mm;
976 int ret;
977
978 /* Notify parent that we're no longer interested in the old VM */
979 tsk = current;
980 old_mm = current->mm;
981 exec_mm_release(tsk, old_mm);
982 if (old_mm)
983 sync_mm_rss(old_mm);
984
985 ret = down_write_killable(&tsk->signal->exec_update_lock);
986 if (ret)
987 return ret;
988
989 if (old_mm) {
990 /*
991 * Make sure that if there is a core dump in progress
992 * for the old mm, we get out and die instead of going
993 * through with the exec. We must hold mmap_lock around
994 * checking core_state and changing tsk->mm.
995 */
996 mmap_read_lock(old_mm);
997 if (unlikely(old_mm->core_state)) {
998 mmap_read_unlock(old_mm);
999 up_write(&tsk->signal->exec_update_lock);
1000 return -EINTR;
1001 }
1002 }
1003
1004 task_lock(tsk);
1005 membarrier_exec_mmap(mm);
1006
1007 local_irq_disable();
1008 active_mm = tsk->active_mm;
1009 tsk->active_mm = mm;
1010 tsk->mm = mm;
1011 /*
1012 * This prevents preemption while active_mm is being loaded and
1013 * it and mm are being updated, which could cause problems for
1014 * lazy tlb mm refcounting when these are updated by context
1015 * switches. Not all architectures can handle irqs off over
1016 * activate_mm yet.
1017 */
1018 if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
1019 local_irq_enable();
1020 activate_mm(active_mm, mm);
1021 if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
1022 local_irq_enable();
1023 tsk->mm->vmacache_seqnum = 0;
1024 vmacache_flush(tsk);
1025 task_unlock(tsk);
1026 if (old_mm) {
1027 mmap_read_unlock(old_mm);
1028 BUG_ON(active_mm != old_mm);
1029 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
1030 mm_update_next_owner(old_mm);
1031 mmput(old_mm);
1032 return 0;
1033 }
1034 mmdrop(active_mm);
1035 return 0;
1036}
1037
1038static int de_thread(struct task_struct *tsk)
1039{
1040 struct signal_struct *sig = tsk->signal;
1041 struct sighand_struct *oldsighand = tsk->sighand;
1042 spinlock_t *lock = &oldsighand->siglock;
1043
1044 if (thread_group_empty(tsk))
1045 goto no_thread_group;
1046
1047 /*
1048 * Kill all other threads in the thread group.
1049 */
1050 spin_lock_irq(lock);
1051 if (signal_group_exit(sig)) {
1052 /*
1053 * Another group action in progress, just
1054 * return so that the signal is processed.
1055 */
1056 spin_unlock_irq(lock);
1057 return -EAGAIN;
1058 }
1059
1060 sig->group_exit_task = tsk;
1061 sig->notify_count = zap_other_threads(tsk);
1062 if (!thread_group_leader(tsk))
1063 sig->notify_count--;
1064
1065 while (sig->notify_count) {
1066 __set_current_state(TASK_KILLABLE);
1067 spin_unlock_irq(lock);
1068 schedule();
1069 if (__fatal_signal_pending(tsk))
1070 goto killed;
1071 spin_lock_irq(lock);
1072 }
1073 spin_unlock_irq(lock);
1074
1075 /*
1076 * At this point all other threads have exited, all we have to
1077 * do is to wait for the thread group leader to become inactive,
1078 * and to assume its PID:
1079 */
1080 if (!thread_group_leader(tsk)) {
1081 struct task_struct *leader = tsk->group_leader;
1082
1083 for (;;) {
1084 cgroup_threadgroup_change_begin(tsk);
1085 write_lock_irq(&tasklist_lock);
1086 /*
1087 * Do this under tasklist_lock to ensure that
1088 * exit_notify() can't miss ->group_exit_task
1089 */
1090 sig->notify_count = -1;
1091 if (likely(leader->exit_state))
1092 break;
1093 __set_current_state(TASK_KILLABLE);
1094 write_unlock_irq(&tasklist_lock);
1095 cgroup_threadgroup_change_end(tsk);
1096 schedule();
1097 if (__fatal_signal_pending(tsk))
1098 goto killed;
1099 }
1100
1101 /*
1102 * The only record we have of the real-time age of a
1103 * process, regardless of execs it's done, is start_time.
1104 * All the past CPU time is accumulated in signal_struct
1105 * from sister threads now dead. But in this non-leader
1106 * exec, nothing survives from the original leader thread,
1107 * whose birth marks the true age of this process now.
1108 * When we take on its identity by switching to its PID, we
1109 * also take its birthdate (always earlier than our own).
1110 */
1111 tsk->start_time = leader->start_time;
1112 tsk->start_boottime = leader->start_boottime;
1113
1114 BUG_ON(!same_thread_group(leader, tsk));
1115 /*
1116 * An exec() starts a new thread group with the
1117 * TGID of the previous thread group. Rehash the
1118 * two threads with a switched PID, and release
1119 * the former thread group leader:
1120 */
1121
1122 /* Become a process group leader with the old leader's pid.
1123 * The old leader becomes a thread of the this thread group.
1124 */
1125 exchange_tids(tsk, leader);
1126 transfer_pid(leader, tsk, PIDTYPE_TGID);
1127 transfer_pid(leader, tsk, PIDTYPE_PGID);
1128 transfer_pid(leader, tsk, PIDTYPE_SID);
1129
1130 list_replace_rcu(&leader->tasks, &tsk->tasks);
1131 list_replace_init(&leader->sibling, &tsk->sibling);
1132
1133 tsk->group_leader = tsk;
1134 leader->group_leader = tsk;
1135
1136 tsk->exit_signal = SIGCHLD;
1137 leader->exit_signal = -1;
1138
1139 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1140 leader->exit_state = EXIT_DEAD;
1141
1142 /*
1143 * We are going to release_task()->ptrace_unlink() silently,
1144 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1145 * the tracer wont't block again waiting for this thread.
1146 */
1147 if (unlikely(leader->ptrace))
1148 __wake_up_parent(leader, leader->parent);
1149 write_unlock_irq(&tasklist_lock);
1150 cgroup_threadgroup_change_end(tsk);
1151
1152 release_task(leader);
1153 }
1154
1155 sig->group_exit_task = NULL;
1156 sig->notify_count = 0;
1157
1158no_thread_group:
1159 /* we have changed execution domain */
1160 tsk->exit_signal = SIGCHLD;
1161
1162 BUG_ON(!thread_group_leader(tsk));
1163 return 0;
1164
1165killed:
1166 /* protects against exit_notify() and __exit_signal() */
1167 read_lock(&tasklist_lock);
1168 sig->group_exit_task = NULL;
1169 sig->notify_count = 0;
1170 read_unlock(&tasklist_lock);
1171 return -EAGAIN;
1172}
1173
1174
1175/*
1176 * This function makes sure the current process has its own signal table,
1177 * so that flush_signal_handlers can later reset the handlers without
1178 * disturbing other processes. (Other processes might share the signal
1179 * table via the CLONE_SIGHAND option to clone().)
1180 */
1181static int unshare_sighand(struct task_struct *me)
1182{
1183 struct sighand_struct *oldsighand = me->sighand;
1184
1185 if (refcount_read(&oldsighand->count) != 1) {
1186 struct sighand_struct *newsighand;
1187 /*
1188 * This ->sighand is shared with the CLONE_SIGHAND
1189 * but not CLONE_THREAD task, switch to the new one.
1190 */
1191 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1192 if (!newsighand)
1193 return -ENOMEM;
1194
1195 refcount_set(&newsighand->count, 1);
1196 memcpy(newsighand->action, oldsighand->action,
1197 sizeof(newsighand->action));
1198
1199 write_lock_irq(&tasklist_lock);
1200 spin_lock(&oldsighand->siglock);
1201 rcu_assign_pointer(me->sighand, newsighand);
1202 spin_unlock(&oldsighand->siglock);
1203 write_unlock_irq(&tasklist_lock);
1204
1205 __cleanup_sighand(oldsighand);
1206 }
1207 return 0;
1208}
1209
1210char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
1211{
1212 task_lock(tsk);
1213 strncpy(buf, tsk->comm, buf_size);
1214 task_unlock(tsk);
1215 return buf;
1216}
1217EXPORT_SYMBOL_GPL(__get_task_comm);
1218
1219/*
1220 * These functions flushes out all traces of the currently running executable
1221 * so that a new one can be started
1222 */
1223
1224void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1225{
1226 task_lock(tsk);
1227 trace_task_rename(tsk, buf);
1228 strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1229 task_unlock(tsk);
1230 perf_event_comm(tsk, exec);
1231}
1232
1233/*
1234 * Calling this is the point of no return. None of the failures will be
1235 * seen by userspace since either the process is already taking a fatal
1236 * signal (via de_thread() or coredump), or will have SEGV raised
1237 * (after exec_mmap()) by search_binary_handler (see below).
1238 */
1239int begin_new_exec(struct linux_binprm * bprm)
1240{
1241 struct task_struct *me = current;
1242 int retval;
1243
1244 /* Once we are committed compute the creds */
1245 retval = bprm_creds_from_file(bprm);
1246 if (retval)
1247 return retval;
1248
1249 /*
1250 * Ensure all future errors are fatal.
1251 */
1252 bprm->point_of_no_return = true;
1253
1254 /*
1255 * Make this the only thread in the thread group.
1256 */
1257 retval = de_thread(me);
1258 if (retval)
1259 goto out;
1260
1261 /*
1262 * Cancel any io_uring activity across execve
1263 */
1264 io_uring_task_cancel();
1265
1266 /* Ensure the files table is not shared. */
1267 retval = unshare_files();
1268 if (retval)
1269 goto out;
1270
1271 /*
1272 * Must be called _before_ exec_mmap() as bprm->mm is
1273 * not visibile until then. This also enables the update
1274 * to be lockless.
1275 */
1276 set_mm_exe_file(bprm->mm, bprm->file);
1277
1278 /* If the binary is not readable then enforce mm->dumpable=0 */
1279 would_dump(bprm, bprm->file);
1280 if (bprm->have_execfd)
1281 would_dump(bprm, bprm->executable);
1282
1283 /*
1284 * Release all of the old mmap stuff
1285 */
1286 acct_arg_size(bprm, 0);
1287 retval = exec_mmap(bprm->mm);
1288 if (retval)
1289 goto out;
1290
1291 bprm->mm = NULL;
1292
1293#ifdef CONFIG_POSIX_TIMERS
1294 exit_itimers(me->signal);
1295 flush_itimer_signals();
1296#endif
1297
1298 /*
1299 * Make the signal table private.
1300 */
1301 retval = unshare_sighand(me);
1302 if (retval)
1303 goto out_unlock;
1304
1305 /*
1306 * Ensure that the uaccess routines can actually operate on userspace
1307 * pointers:
1308 */
1309 force_uaccess_begin();
1310
1311 me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
1312 PF_NOFREEZE | PF_NO_SETAFFINITY);
1313 flush_thread();
1314 me->personality &= ~bprm->per_clear;
1315
1316 clear_syscall_work_syscall_user_dispatch(me);
1317
1318 /*
1319 * We have to apply CLOEXEC before we change whether the process is
1320 * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1321 * trying to access the should-be-closed file descriptors of a process
1322 * undergoing exec(2).
1323 */
1324 do_close_on_exec(me->files);
1325
1326 if (bprm->secureexec) {
1327 /* Make sure parent cannot signal privileged process. */
1328 me->pdeath_signal = 0;
1329
1330 /*
1331 * For secureexec, reset the stack limit to sane default to
1332 * avoid bad behavior from the prior rlimits. This has to
1333 * happen before arch_pick_mmap_layout(), which examines
1334 * RLIMIT_STACK, but after the point of no return to avoid
1335 * needing to clean up the change on failure.
1336 */
1337 if (bprm->rlim_stack.rlim_cur > _STK_LIM)
1338 bprm->rlim_stack.rlim_cur = _STK_LIM;
1339 }
1340
1341 me->sas_ss_sp = me->sas_ss_size = 0;
1342
1343 /*
1344 * Figure out dumpability. Note that this checking only of current
1345 * is wrong, but userspace depends on it. This should be testing
1346 * bprm->secureexec instead.
1347 */
1348 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
1349 !(uid_eq(current_euid(), current_uid()) &&
1350 gid_eq(current_egid(), current_gid())))
1351 set_dumpable(current->mm, suid_dumpable);
1352 else
1353 set_dumpable(current->mm, SUID_DUMP_USER);
1354
1355 perf_event_exec();
1356 __set_task_comm(me, kbasename(bprm->filename), true);
1357
1358 /* An exec changes our domain. We are no longer part of the thread
1359 group */
1360 WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1);
1361 flush_signal_handlers(me, 0);
1362
1363 /*
1364 * install the new credentials for this executable
1365 */
1366 security_bprm_committing_creds(bprm);
1367
1368 commit_creds(bprm->cred);
1369 bprm->cred = NULL;
1370
1371 /*
1372 * Disable monitoring for regular users
1373 * when executing setuid binaries. Must
1374 * wait until new credentials are committed
1375 * by commit_creds() above
1376 */
1377 if (get_dumpable(me->mm) != SUID_DUMP_USER)
1378 perf_event_exit_task(me);
1379 /*
1380 * cred_guard_mutex must be held at least to this point to prevent
1381 * ptrace_attach() from altering our determination of the task's
1382 * credentials; any time after this it may be unlocked.
1383 */
1384 security_bprm_committed_creds(bprm);
1385
1386 /* Pass the opened binary to the interpreter. */
1387 if (bprm->have_execfd) {
1388 retval = get_unused_fd_flags(0);
1389 if (retval < 0)
1390 goto out_unlock;
1391 fd_install(retval, bprm->executable);
1392 bprm->executable = NULL;
1393 bprm->execfd = retval;
1394 }
1395 return 0;
1396
1397out_unlock:
1398 up_write(&me->signal->exec_update_lock);
1399out:
1400 return retval;
1401}
1402EXPORT_SYMBOL(begin_new_exec);
1403
1404void would_dump(struct linux_binprm *bprm, struct file *file)
1405{
1406 struct inode *inode = file_inode(file);
1407 if (inode_permission(inode, MAY_READ) < 0) {
1408 struct user_namespace *old, *user_ns;
1409 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1410
1411 /* Ensure mm->user_ns contains the executable */
1412 user_ns = old = bprm->mm->user_ns;
1413 while ((user_ns != &init_user_ns) &&
1414 !privileged_wrt_inode_uidgid(user_ns, inode))
1415 user_ns = user_ns->parent;
1416
1417 if (old != user_ns) {
1418 bprm->mm->user_ns = get_user_ns(user_ns);
1419 put_user_ns(old);
1420 }
1421 }
1422}
1423EXPORT_SYMBOL(would_dump);
1424
1425void setup_new_exec(struct linux_binprm * bprm)
1426{
1427 /* Setup things that can depend upon the personality */
1428 struct task_struct *me = current;
1429
1430 arch_pick_mmap_layout(me->mm, &bprm->rlim_stack);
1431
1432 arch_setup_new_exec();
1433
1434 /* Set the new mm task size. We have to do that late because it may
1435 * depend on TIF_32BIT which is only updated in flush_thread() on
1436 * some architectures like powerpc
1437 */
1438 me->mm->task_size = TASK_SIZE;
1439 up_write(&me->signal->exec_update_lock);
1440 mutex_unlock(&me->signal->cred_guard_mutex);
1441}
1442EXPORT_SYMBOL(setup_new_exec);
1443
1444/* Runs immediately before start_thread() takes over. */
1445void finalize_exec(struct linux_binprm *bprm)
1446{
1447 /* Store any stack rlimit changes before starting thread. */
1448 task_lock(current->group_leader);
1449 current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack;
1450 task_unlock(current->group_leader);
1451}
1452EXPORT_SYMBOL(finalize_exec);
1453
1454/*
1455 * Prepare credentials and lock ->cred_guard_mutex.
1456 * setup_new_exec() commits the new creds and drops the lock.
1457 * Or, if exec fails before, free_bprm() should release ->cred and
1458 * and unlock.
1459 */
1460static int prepare_bprm_creds(struct linux_binprm *bprm)
1461{
1462 if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1463 return -ERESTARTNOINTR;
1464
1465 bprm->cred = prepare_exec_creds();
1466 if (likely(bprm->cred))
1467 return 0;
1468
1469 mutex_unlock(&current->signal->cred_guard_mutex);
1470 return -ENOMEM;
1471}
1472
1473static void free_bprm(struct linux_binprm *bprm)
1474{
1475 if (bprm->mm) {
1476 acct_arg_size(bprm, 0);
1477 mmput(bprm->mm);
1478 }
1479 free_arg_pages(bprm);
1480 if (bprm->cred) {
1481 mutex_unlock(&current->signal->cred_guard_mutex);
1482 abort_creds(bprm->cred);
1483 }
1484 if (bprm->file) {
1485 allow_write_access(bprm->file);
1486 fput(bprm->file);
1487 }
1488 if (bprm->executable)
1489 fput(bprm->executable);
1490 /* If a binfmt changed the interp, free it. */
1491 if (bprm->interp != bprm->filename)
1492 kfree(bprm->interp);
1493 kfree(bprm->fdpath);
1494 kfree(bprm);
1495}
1496
1497static struct linux_binprm *alloc_bprm(int fd, struct filename *filename)
1498{
1499 struct linux_binprm *bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1500 int retval = -ENOMEM;
1501 if (!bprm)
1502 goto out;
1503
1504 if (fd == AT_FDCWD || filename->name[0] == '/') {
1505 bprm->filename = filename->name;
1506 } else {
1507 if (filename->name[0] == '\0')
1508 bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd);
1509 else
1510 bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s",
1511 fd, filename->name);
1512 if (!bprm->fdpath)
1513 goto out_free;
1514
1515 bprm->filename = bprm->fdpath;
1516 }
1517 bprm->interp = bprm->filename;
1518
1519 retval = bprm_mm_init(bprm);
1520 if (retval)
1521 goto out_free;
1522 return bprm;
1523
1524out_free:
1525 free_bprm(bprm);
1526out:
1527 return ERR_PTR(retval);
1528}
1529
1530int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
1531{
1532 /* If a binfmt changed the interp, free it first. */
1533 if (bprm->interp != bprm->filename)
1534 kfree(bprm->interp);
1535 bprm->interp = kstrdup(interp, GFP_KERNEL);
1536 if (!bprm->interp)
1537 return -ENOMEM;
1538 return 0;
1539}
1540EXPORT_SYMBOL(bprm_change_interp);
1541
1542/*
1543 * determine how safe it is to execute the proposed program
1544 * - the caller must hold ->cred_guard_mutex to protect against
1545 * PTRACE_ATTACH or seccomp thread-sync
1546 */
1547static void check_unsafe_exec(struct linux_binprm *bprm)
1548{
1549 struct task_struct *p = current, *t;
1550 unsigned n_fs;
1551
1552 if (p->ptrace)
1553 bprm->unsafe |= LSM_UNSAFE_PTRACE;
1554
1555 /*
1556 * This isn't strictly necessary, but it makes it harder for LSMs to
1557 * mess up.
1558 */
1559 if (task_no_new_privs(current))
1560 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1561
1562 t = p;
1563 n_fs = 1;
1564 spin_lock(&p->fs->lock);
1565 rcu_read_lock();
1566 while_each_thread(p, t) {
1567 if (t->fs == p->fs)
1568 n_fs++;
1569 }
1570 rcu_read_unlock();
1571
1572 if (p->fs->users > n_fs)
1573 bprm->unsafe |= LSM_UNSAFE_SHARE;
1574 else
1575 p->fs->in_exec = 1;
1576 spin_unlock(&p->fs->lock);
1577}
1578
1579static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
1580{
1581 /* Handle suid and sgid on files */
1582 struct inode *inode;
1583 unsigned int mode;
1584 kuid_t uid;
1585 kgid_t gid;
1586
1587 if (!mnt_may_suid(file->f_path.mnt))
1588 return;
1589
1590 if (task_no_new_privs(current))
1591 return;
1592
1593 inode = file->f_path.dentry->d_inode;
1594 mode = READ_ONCE(inode->i_mode);
1595 if (!(mode & (S_ISUID|S_ISGID)))
1596 return;
1597
1598 /* Be careful if suid/sgid is set */
1599 inode_lock(inode);
1600
1601 /* reload atomically mode/uid/gid now that lock held */
1602 mode = inode->i_mode;
1603 uid = inode->i_uid;
1604 gid = inode->i_gid;
1605 inode_unlock(inode);
1606
1607 /* We ignore suid/sgid if there are no mappings for them in the ns */
1608 if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
1609 !kgid_has_mapping(bprm->cred->user_ns, gid))
1610 return;
1611
1612 if (mode & S_ISUID) {
1613 bprm->per_clear |= PER_CLEAR_ON_SETID;
1614 bprm->cred->euid = uid;
1615 }
1616
1617 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1618 bprm->per_clear |= PER_CLEAR_ON_SETID;
1619 bprm->cred->egid = gid;
1620 }
1621}
1622
1623/*
1624 * Compute brpm->cred based upon the final binary.
1625 */
1626static int bprm_creds_from_file(struct linux_binprm *bprm)
1627{
1628 /* Compute creds based on which file? */
1629 struct file *file = bprm->execfd_creds ? bprm->executable : bprm->file;
1630
1631 bprm_fill_uid(bprm, file);
1632 return security_bprm_creds_from_file(bprm, file);
1633}
1634
1635/*
1636 * Fill the binprm structure from the inode.
1637 * Read the first BINPRM_BUF_SIZE bytes
1638 *
1639 * This may be called multiple times for binary chains (scripts for example).
1640 */
1641static int prepare_binprm(struct linux_binprm *bprm)
1642{
1643 loff_t pos = 0;
1644
1645 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1646 return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
1647}
1648
1649/*
1650 * Arguments are '\0' separated strings found at the location bprm->p
1651 * points to; chop off the first by relocating brpm->p to right after
1652 * the first '\0' encountered.
1653 */
1654int remove_arg_zero(struct linux_binprm *bprm)
1655{
1656 int ret = 0;
1657 unsigned long offset;
1658 char *kaddr;
1659 struct page *page;
1660
1661 if (!bprm->argc)
1662 return 0;
1663
1664 do {
1665 offset = bprm->p & ~PAGE_MASK;
1666 page = get_arg_page(bprm, bprm->p, 0);
1667 if (!page) {
1668 ret = -EFAULT;
1669 goto out;
1670 }
1671 kaddr = kmap_atomic(page);
1672
1673 for (; offset < PAGE_SIZE && kaddr[offset];
1674 offset++, bprm->p++)
1675 ;
1676
1677 kunmap_atomic(kaddr);
1678 put_arg_page(page);
1679 } while (offset == PAGE_SIZE);
1680
1681 bprm->p++;
1682 bprm->argc--;
1683 ret = 0;
1684
1685out:
1686 return ret;
1687}
1688EXPORT_SYMBOL(remove_arg_zero);
1689
1690#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1691/*
1692 * cycle the list of binary formats handler, until one recognizes the image
1693 */
1694static int search_binary_handler(struct linux_binprm *bprm)
1695{
1696 bool need_retry = IS_ENABLED(CONFIG_MODULES);
1697 struct linux_binfmt *fmt;
1698 int retval;
1699
1700 retval = prepare_binprm(bprm);
1701 if (retval < 0)
1702 return retval;
1703
1704 retval = security_bprm_check(bprm);
1705 if (retval)
1706 return retval;
1707
1708 retval = -ENOENT;
1709 retry:
1710 read_lock(&binfmt_lock);
1711 list_for_each_entry(fmt, &formats, lh) {
1712 if (!try_module_get(fmt->module))
1713 continue;
1714 read_unlock(&binfmt_lock);
1715
1716 retval = fmt->load_binary(bprm);
1717
1718 read_lock(&binfmt_lock);
1719 put_binfmt(fmt);
1720 if (bprm->point_of_no_return || (retval != -ENOEXEC)) {
1721 read_unlock(&binfmt_lock);
1722 return retval;
1723 }
1724 }
1725 read_unlock(&binfmt_lock);
1726
1727 if (need_retry) {
1728 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1729 printable(bprm->buf[2]) && printable(bprm->buf[3]))
1730 return retval;
1731 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1732 return retval;
1733 need_retry = false;
1734 goto retry;
1735 }
1736
1737 return retval;
1738}
1739
1740static int exec_binprm(struct linux_binprm *bprm)
1741{
1742 pid_t old_pid, old_vpid;
1743 int ret, depth;
1744
1745 /* Need to fetch pid before load_binary changes it */
1746 old_pid = current->pid;
1747 rcu_read_lock();
1748 old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1749 rcu_read_unlock();
1750
1751 /* This allows 4 levels of binfmt rewrites before failing hard. */
1752 for (depth = 0;; depth++) {
1753 struct file *exec;
1754 if (depth > 5)
1755 return -ELOOP;
1756
1757 ret = search_binary_handler(bprm);
1758 if (ret < 0)
1759 return ret;
1760 if (!bprm->interpreter)
1761 break;
1762
1763 exec = bprm->file;
1764 bprm->file = bprm->interpreter;
1765 bprm->interpreter = NULL;
1766
1767 allow_write_access(exec);
1768 if (unlikely(bprm->have_execfd)) {
1769 if (bprm->executable) {
1770 fput(exec);
1771 return -ENOEXEC;
1772 }
1773 bprm->executable = exec;
1774 } else
1775 fput(exec);
1776 }
1777
1778 audit_bprm(bprm);
1779 trace_sched_process_exec(current, old_pid, bprm);
1780 ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1781 proc_exec_connector(current);
1782 return 0;
1783}
1784
1785/*
1786 * sys_execve() executes a new program.
1787 */
1788static int bprm_execve(struct linux_binprm *bprm,
1789 int fd, struct filename *filename, int flags)
1790{
1791 struct file *file;
1792 int retval;
1793
1794 retval = prepare_bprm_creds(bprm);
1795 if (retval)
1796 return retval;
1797
1798 check_unsafe_exec(bprm);
1799 current->in_execve = 1;
1800
1801 file = do_open_execat(fd, filename, flags);
1802 retval = PTR_ERR(file);
1803 if (IS_ERR(file))
1804 goto out_unmark;
1805
1806 sched_exec();
1807
1808 bprm->file = file;
1809 /*
1810 * Record that a name derived from an O_CLOEXEC fd will be
1811 * inaccessible after exec. This allows the code in exec to
1812 * choose to fail when the executable is not mmaped into the
1813 * interpreter and an open file descriptor is not passed to
1814 * the interpreter. This makes for a better user experience
1815 * than having the interpreter start and then immediately fail
1816 * when it finds the executable is inaccessible.
1817 */
1818 if (bprm->fdpath && get_close_on_exec(fd))
1819 bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1820
1821 /* Set the unchanging part of bprm->cred */
1822 retval = security_bprm_creds_for_exec(bprm);
1823 if (retval)
1824 goto out;
1825
1826 retval = exec_binprm(bprm);
1827 if (retval < 0)
1828 goto out;
1829
1830 /* execve succeeded */
1831 current->fs->in_exec = 0;
1832 current->in_execve = 0;
1833 rseq_execve(current);
1834 acct_update_integrals(current);
1835 task_numa_free(current, false);
1836 return retval;
1837
1838out:
1839 /*
1840 * If past the point of no return ensure the the code never
1841 * returns to the userspace process. Use an existing fatal
1842 * signal if present otherwise terminate the process with
1843 * SIGSEGV.
1844 */
1845 if (bprm->point_of_no_return && !fatal_signal_pending(current))
1846 force_sigsegv(SIGSEGV);
1847
1848out_unmark:
1849 current->fs->in_exec = 0;
1850 current->in_execve = 0;
1851
1852 return retval;
1853}
1854
1855static int do_execveat_common(int fd, struct filename *filename,
1856 struct user_arg_ptr argv,
1857 struct user_arg_ptr envp,
1858 int flags)
1859{
1860 struct linux_binprm *bprm;
1861 int retval;
1862
1863 if (IS_ERR(filename))
1864 return PTR_ERR(filename);
1865
1866 /*
1867 * We move the actual failure in case of RLIMIT_NPROC excess from
1868 * set*uid() to execve() because too many poorly written programs
1869 * don't check setuid() return code. Here we additionally recheck
1870 * whether NPROC limit is still exceeded.
1871 */
1872 if ((current->flags & PF_NPROC_EXCEEDED) &&
1873 atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
1874 retval = -EAGAIN;
1875 goto out_ret;
1876 }
1877
1878 /* We're below the limit (still or again), so we don't want to make
1879 * further execve() calls fail. */
1880 current->flags &= ~PF_NPROC_EXCEEDED;
1881
1882 bprm = alloc_bprm(fd, filename);
1883 if (IS_ERR(bprm)) {
1884 retval = PTR_ERR(bprm);
1885 goto out_ret;
1886 }
1887
1888 retval = count(argv, MAX_ARG_STRINGS);
1889 if (retval < 0)
1890 goto out_free;
1891 bprm->argc = retval;
1892
1893 retval = count(envp, MAX_ARG_STRINGS);
1894 if (retval < 0)
1895 goto out_free;
1896 bprm->envc = retval;
1897
1898 retval = bprm_stack_limits(bprm);
1899 if (retval < 0)
1900 goto out_free;
1901
1902 retval = copy_string_kernel(bprm->filename, bprm);
1903 if (retval < 0)
1904 goto out_free;
1905 bprm->exec = bprm->p;
1906
1907 retval = copy_strings(bprm->envc, envp, bprm);
1908 if (retval < 0)
1909 goto out_free;
1910
1911 retval = copy_strings(bprm->argc, argv, bprm);
1912 if (retval < 0)
1913 goto out_free;
1914
1915 retval = bprm_execve(bprm, fd, filename, flags);
1916out_free:
1917 free_bprm(bprm);
1918
1919out_ret:
1920 putname(filename);
1921 return retval;
1922}
1923
1924int kernel_execve(const char *kernel_filename,
1925 const char *const *argv, const char *const *envp)
1926{
1927 struct filename *filename;
1928 struct linux_binprm *bprm;
1929 int fd = AT_FDCWD;
1930 int retval;
1931
1932 filename = getname_kernel(kernel_filename);
1933 if (IS_ERR(filename))
1934 return PTR_ERR(filename);
1935
1936 bprm = alloc_bprm(fd, filename);
1937 if (IS_ERR(bprm)) {
1938 retval = PTR_ERR(bprm);
1939 goto out_ret;
1940 }
1941
1942 retval = count_strings_kernel(argv);
1943 if (retval < 0)
1944 goto out_free;
1945 bprm->argc = retval;
1946
1947 retval = count_strings_kernel(envp);
1948 if (retval < 0)
1949 goto out_free;
1950 bprm->envc = retval;
1951
1952 retval = bprm_stack_limits(bprm);
1953 if (retval < 0)
1954 goto out_free;
1955
1956 retval = copy_string_kernel(bprm->filename, bprm);
1957 if (retval < 0)
1958 goto out_free;
1959 bprm->exec = bprm->p;
1960
1961 retval = copy_strings_kernel(bprm->envc, envp, bprm);
1962 if (retval < 0)
1963 goto out_free;
1964
1965 retval = copy_strings_kernel(bprm->argc, argv, bprm);
1966 if (retval < 0)
1967 goto out_free;
1968
1969 retval = bprm_execve(bprm, fd, filename, 0);
1970out_free:
1971 free_bprm(bprm);
1972out_ret:
1973 putname(filename);
1974 return retval;
1975}
1976
1977static int do_execve(struct filename *filename,
1978 const char __user *const __user *__argv,
1979 const char __user *const __user *__envp)
1980{
1981 struct user_arg_ptr argv = { .ptr.native = __argv };
1982 struct user_arg_ptr envp = { .ptr.native = __envp };
1983 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1984}
1985
1986static int do_execveat(int fd, struct filename *filename,
1987 const char __user *const __user *__argv,
1988 const char __user *const __user *__envp,
1989 int flags)
1990{
1991 struct user_arg_ptr argv = { .ptr.native = __argv };
1992 struct user_arg_ptr envp = { .ptr.native = __envp };
1993
1994 return do_execveat_common(fd, filename, argv, envp, flags);
1995}
1996
1997#ifdef CONFIG_COMPAT
1998static int compat_do_execve(struct filename *filename,
1999 const compat_uptr_t __user *__argv,
2000 const compat_uptr_t __user *__envp)
2001{
2002 struct user_arg_ptr argv = {
2003 .is_compat = true,
2004 .ptr.compat = __argv,
2005 };
2006 struct user_arg_ptr envp = {
2007 .is_compat = true,
2008 .ptr.compat = __envp,
2009 };
2010 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
2011}
2012
2013static int compat_do_execveat(int fd, struct filename *filename,
2014 const compat_uptr_t __user *__argv,
2015 const compat_uptr_t __user *__envp,
2016 int flags)
2017{
2018 struct user_arg_ptr argv = {
2019 .is_compat = true,
2020 .ptr.compat = __argv,
2021 };
2022 struct user_arg_ptr envp = {
2023 .is_compat = true,
2024 .ptr.compat = __envp,
2025 };
2026 return do_execveat_common(fd, filename, argv, envp, flags);
2027}
2028#endif
2029
2030void set_binfmt(struct linux_binfmt *new)
2031{
2032 struct mm_struct *mm = current->mm;
2033
2034 if (mm->binfmt)
2035 module_put(mm->binfmt->module);
2036
2037 mm->binfmt = new;
2038 if (new)
2039 __module_get(new->module);
2040}
2041EXPORT_SYMBOL(set_binfmt);
2042
2043/*
2044 * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
2045 */
2046void set_dumpable(struct mm_struct *mm, int value)
2047{
2048 if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
2049 return;
2050
2051 set_mask_bits(&mm->flags, MMF_DUMPABLE_MASK, value);
2052}
2053
2054SYSCALL_DEFINE3(execve,
2055 const char __user *, filename,
2056 const char __user *const __user *, argv,
2057 const char __user *const __user *, envp)
2058{
2059 return do_execve(getname(filename), argv, envp);
2060}
2061
2062SYSCALL_DEFINE5(execveat,
2063 int, fd, const char __user *, filename,
2064 const char __user *const __user *, argv,
2065 const char __user *const __user *, envp,
2066 int, flags)
2067{
2068 int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
2069
2070 return do_execveat(fd,
2071 getname_flags(filename, lookup_flags, NULL),
2072 argv, envp, flags);
2073}
2074
2075#ifdef CONFIG_COMPAT
2076COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
2077 const compat_uptr_t __user *, argv,
2078 const compat_uptr_t __user *, envp)
2079{
2080 return compat_do_execve(getname(filename), argv, envp);
2081}
2082
2083COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
2084 const char __user *, filename,
2085 const compat_uptr_t __user *, argv,
2086 const compat_uptr_t __user *, envp,
2087 int, flags)
2088{
2089 int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
2090
2091 return compat_do_execveat(fd,
2092 getname_flags(filename, lookup_flags, NULL),
2093 argv, envp, flags);
2094}
2095#endif