projects/linux·blob v4.20 · refs

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1/*
2 * linux/fs/exec.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7/*
8 * #!-checking implemented by tytso.
9 */
10/*
11 * Demand-loading implemented 01.12.91 - no need to read anything but
12 * the header into memory. The inode of the executable is put into
13 * "current->executable", and page faults do the actual loading. Clean.
14 *
15 * Once more I can proudly say that linux stood up to being changed: it
16 * was less than 2 hours work to get demand-loading completely implemented.
17 *
18 * Demand loading changed July 1993 by Eric Youngdale. Use mmap instead,
19 * current->executable is only used by the procfs. This allows a dispatch
20 * table to check for several different types of binary formats. We keep
21 * trying until we recognize the file or we run out of supported binary
22 * formats.
23 */
24
25#include <linux/slab.h>
26#include <linux/file.h>
27#include <linux/fdtable.h>
28#include <linux/mm.h>
29#include <linux/vmacache.h>
30#include <linux/stat.h>
31#include <linux/fcntl.h>
32#include <linux/swap.h>
33#include <linux/string.h>
34#include <linux/init.h>
35#include <linux/sched/mm.h>
36#include <linux/sched/coredump.h>
37#include <linux/sched/signal.h>
38#include <linux/sched/numa_balancing.h>
39#include <linux/sched/task.h>
40#include <linux/pagemap.h>
41#include <linux/perf_event.h>
42#include <linux/highmem.h>
43#include <linux/spinlock.h>
44#include <linux/key.h>
45#include <linux/personality.h>
46#include <linux/binfmts.h>
47#include <linux/utsname.h>
48#include <linux/pid_namespace.h>
49#include <linux/module.h>
50#include <linux/namei.h>
51#include <linux/mount.h>
52#include <linux/security.h>
53#include <linux/syscalls.h>
54#include <linux/tsacct_kern.h>
55#include <linux/cn_proc.h>
56#include <linux/audit.h>
57#include <linux/tracehook.h>
58#include <linux/kmod.h>
59#include <linux/fsnotify.h>
60#include <linux/fs_struct.h>
61#include <linux/pipe_fs_i.h>
62#include <linux/oom.h>
63#include <linux/compat.h>
64#include <linux/vmalloc.h>
65
66#include <linux/uaccess.h>
67#include <asm/mmu_context.h>
68#include <asm/tlb.h>
69
70#include <trace/events/task.h>
71#include "internal.h"
72
73#include <trace/events/sched.h>
74
75int suid_dumpable = 0;
76
77static LIST_HEAD(formats);
78static DEFINE_RWLOCK(binfmt_lock);
79
80void __register_binfmt(struct linux_binfmt * fmt, int insert)
81{
82 BUG_ON(!fmt);
83 if (WARN_ON(!fmt->load_binary))
84 return;
85 write_lock(&binfmt_lock);
86 insert ? list_add(&fmt->lh, &formats) :
87 list_add_tail(&fmt->lh, &formats);
88 write_unlock(&binfmt_lock);
89}
90
91EXPORT_SYMBOL(__register_binfmt);
92
93void unregister_binfmt(struct linux_binfmt * fmt)
94{
95 write_lock(&binfmt_lock);
96 list_del(&fmt->lh);
97 write_unlock(&binfmt_lock);
98}
99
100EXPORT_SYMBOL(unregister_binfmt);
101
102static inline void put_binfmt(struct linux_binfmt * fmt)
103{
104 module_put(fmt->module);
105}
106
107bool path_noexec(const struct path *path)
108{
109 return (path->mnt->mnt_flags & MNT_NOEXEC) ||
110 (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
111}
112
113#ifdef CONFIG_USELIB
114/*
115 * Note that a shared library must be both readable and executable due to
116 * security reasons.
117 *
118 * Also note that we take the address to load from from the file itself.
119 */
120SYSCALL_DEFINE1(uselib, const char __user *, library)
121{
122 struct linux_binfmt *fmt;
123 struct file *file;
124 struct filename *tmp = getname(library);
125 int error = PTR_ERR(tmp);
126 static const struct open_flags uselib_flags = {
127 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
128 .acc_mode = MAY_READ | MAY_EXEC,
129 .intent = LOOKUP_OPEN,
130 .lookup_flags = LOOKUP_FOLLOW,
131 };
132
133 if (IS_ERR(tmp))
134 goto out;
135
136 file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
137 putname(tmp);
138 error = PTR_ERR(file);
139 if (IS_ERR(file))
140 goto out;
141
142 error = -EINVAL;
143 if (!S_ISREG(file_inode(file)->i_mode))
144 goto exit;
145
146 error = -EACCES;
147 if (path_noexec(&file->f_path))
148 goto exit;
149
150 fsnotify_open(file);
151
152 error = -ENOEXEC;
153
154 read_lock(&binfmt_lock);
155 list_for_each_entry(fmt, &formats, lh) {
156 if (!fmt->load_shlib)
157 continue;
158 if (!try_module_get(fmt->module))
159 continue;
160 read_unlock(&binfmt_lock);
161 error = fmt->load_shlib(file);
162 read_lock(&binfmt_lock);
163 put_binfmt(fmt);
164 if (error != -ENOEXEC)
165 break;
166 }
167 read_unlock(&binfmt_lock);
168exit:
169 fput(file);
170out:
171 return error;
172}
173#endif /* #ifdef CONFIG_USELIB */
174
175#ifdef CONFIG_MMU
176/*
177 * The nascent bprm->mm is not visible until exec_mmap() but it can
178 * use a lot of memory, account these pages in current->mm temporary
179 * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
180 * change the counter back via acct_arg_size(0).
181 */
182static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
183{
184 struct mm_struct *mm = current->mm;
185 long diff = (long)(pages - bprm->vma_pages);
186
187 if (!mm || !diff)
188 return;
189
190 bprm->vma_pages = pages;
191 add_mm_counter(mm, MM_ANONPAGES, diff);
192}
193
194static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
195 int write)
196{
197 struct page *page;
198 int ret;
199 unsigned int gup_flags = FOLL_FORCE;
200
201#ifdef CONFIG_STACK_GROWSUP
202 if (write) {
203 ret = expand_downwards(bprm->vma, pos);
204 if (ret < 0)
205 return NULL;
206 }
207#endif
208
209 if (write)
210 gup_flags |= FOLL_WRITE;
211
212 /*
213 * We are doing an exec(). 'current' is the process
214 * doing the exec and bprm->mm is the new process's mm.
215 */
216 ret = get_user_pages_remote(current, bprm->mm, pos, 1, gup_flags,
217 &page, NULL, NULL);
218 if (ret <= 0)
219 return NULL;
220
221 if (write) {
222 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
223 unsigned long ptr_size, limit;
224
225 /*
226 * Since the stack will hold pointers to the strings, we
227 * must account for them as well.
228 *
229 * The size calculation is the entire vma while each arg page is
230 * built, so each time we get here it's calculating how far it
231 * is currently (rather than each call being just the newly
232 * added size from the arg page). As a result, we need to
233 * always add the entire size of the pointers, so that on the
234 * last call to get_arg_page() we'll actually have the entire
235 * correct size.
236 */
237 ptr_size = (bprm->argc + bprm->envc) * sizeof(void *);
238 if (ptr_size > ULONG_MAX - size)
239 goto fail;
240 size += ptr_size;
241
242 acct_arg_size(bprm, size / PAGE_SIZE);
243
244 /*
245 * We've historically supported up to 32 pages (ARG_MAX)
246 * of argument strings even with small stacks
247 */
248 if (size <= ARG_MAX)
249 return page;
250
251 /*
252 * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
253 * (whichever is smaller) for the argv+env strings.
254 * This ensures that:
255 * - the remaining binfmt code will not run out of stack space,
256 * - the program will have a reasonable amount of stack left
257 * to work from.
258 */
259 limit = _STK_LIM / 4 * 3;
260 limit = min(limit, bprm->rlim_stack.rlim_cur / 4);
261 if (size > limit)
262 goto fail;
263 }
264
265 return page;
266
267fail:
268 put_page(page);
269 return NULL;
270}
271
272static void put_arg_page(struct page *page)
273{
274 put_page(page);
275}
276
277static void free_arg_pages(struct linux_binprm *bprm)
278{
279}
280
281static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
282 struct page *page)
283{
284 flush_cache_page(bprm->vma, pos, page_to_pfn(page));
285}
286
287static int __bprm_mm_init(struct linux_binprm *bprm)
288{
289 int err;
290 struct vm_area_struct *vma = NULL;
291 struct mm_struct *mm = bprm->mm;
292
293 bprm->vma = vma = vm_area_alloc(mm);
294 if (!vma)
295 return -ENOMEM;
296 vma_set_anonymous(vma);
297
298 if (down_write_killable(&mm->mmap_sem)) {
299 err = -EINTR;
300 goto err_free;
301 }
302
303 /*
304 * Place the stack at the largest stack address the architecture
305 * supports. Later, we'll move this to an appropriate place. We don't
306 * use STACK_TOP because that can depend on attributes which aren't
307 * configured yet.
308 */
309 BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
310 vma->vm_end = STACK_TOP_MAX;
311 vma->vm_start = vma->vm_end - PAGE_SIZE;
312 vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
313 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
314
315 err = insert_vm_struct(mm, vma);
316 if (err)
317 goto err;
318
319 mm->stack_vm = mm->total_vm = 1;
320 arch_bprm_mm_init(mm, vma);
321 up_write(&mm->mmap_sem);
322 bprm->p = vma->vm_end - sizeof(void *);
323 return 0;
324err:
325 up_write(&mm->mmap_sem);
326err_free:
327 bprm->vma = NULL;
328 vm_area_free(vma);
329 return err;
330}
331
332static bool valid_arg_len(struct linux_binprm *bprm, long len)
333{
334 return len <= MAX_ARG_STRLEN;
335}
336
337#else
338
339static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
340{
341}
342
343static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
344 int write)
345{
346 struct page *page;
347
348 page = bprm->page[pos / PAGE_SIZE];
349 if (!page && write) {
350 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
351 if (!page)
352 return NULL;
353 bprm->page[pos / PAGE_SIZE] = page;
354 }
355
356 return page;
357}
358
359static void put_arg_page(struct page *page)
360{
361}
362
363static void free_arg_page(struct linux_binprm *bprm, int i)
364{
365 if (bprm->page[i]) {
366 __free_page(bprm->page[i]);
367 bprm->page[i] = NULL;
368 }
369}
370
371static void free_arg_pages(struct linux_binprm *bprm)
372{
373 int i;
374
375 for (i = 0; i < MAX_ARG_PAGES; i++)
376 free_arg_page(bprm, i);
377}
378
379static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
380 struct page *page)
381{
382}
383
384static int __bprm_mm_init(struct linux_binprm *bprm)
385{
386 bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
387 return 0;
388}
389
390static bool valid_arg_len(struct linux_binprm *bprm, long len)
391{
392 return len <= bprm->p;
393}
394
395#endif /* CONFIG_MMU */
396
397/*
398 * Create a new mm_struct and populate it with a temporary stack
399 * vm_area_struct. We don't have enough context at this point to set the stack
400 * flags, permissions, and offset, so we use temporary values. We'll update
401 * them later in setup_arg_pages().
402 */
403static int bprm_mm_init(struct linux_binprm *bprm)
404{
405 int err;
406 struct mm_struct *mm = NULL;
407
408 bprm->mm = mm = mm_alloc();
409 err = -ENOMEM;
410 if (!mm)
411 goto err;
412
413 /* Save current stack limit for all calculations made during exec. */
414 task_lock(current->group_leader);
415 bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK];
416 task_unlock(current->group_leader);
417
418 err = __bprm_mm_init(bprm);
419 if (err)
420 goto err;
421
422 return 0;
423
424err:
425 if (mm) {
426 bprm->mm = NULL;
427 mmdrop(mm);
428 }
429
430 return err;
431}
432
433struct user_arg_ptr {
434#ifdef CONFIG_COMPAT
435 bool is_compat;
436#endif
437 union {
438 const char __user *const __user *native;
439#ifdef CONFIG_COMPAT
440 const compat_uptr_t __user *compat;
441#endif
442 } ptr;
443};
444
445static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
446{
447 const char __user *native;
448
449#ifdef CONFIG_COMPAT
450 if (unlikely(argv.is_compat)) {
451 compat_uptr_t compat;
452
453 if (get_user(compat, argv.ptr.compat + nr))
454 return ERR_PTR(-EFAULT);
455
456 return compat_ptr(compat);
457 }
458#endif
459
460 if (get_user(native, argv.ptr.native + nr))
461 return ERR_PTR(-EFAULT);
462
463 return native;
464}
465
466/*
467 * count() counts the number of strings in array ARGV.
468 */
469static int count(struct user_arg_ptr argv, int max)
470{
471 int i = 0;
472
473 if (argv.ptr.native != NULL) {
474 for (;;) {
475 const char __user *p = get_user_arg_ptr(argv, i);
476
477 if (!p)
478 break;
479
480 if (IS_ERR(p))
481 return -EFAULT;
482
483 if (i >= max)
484 return -E2BIG;
485 ++i;
486
487 if (fatal_signal_pending(current))
488 return -ERESTARTNOHAND;
489 cond_resched();
490 }
491 }
492 return i;
493}
494
495/*
496 * 'copy_strings()' copies argument/environment strings from the old
497 * processes's memory to the new process's stack. The call to get_user_pages()
498 * ensures the destination page is created and not swapped out.
499 */
500static int copy_strings(int argc, struct user_arg_ptr argv,
501 struct linux_binprm *bprm)
502{
503 struct page *kmapped_page = NULL;
504 char *kaddr = NULL;
505 unsigned long kpos = 0;
506 int ret;
507
508 while (argc-- > 0) {
509 const char __user *str;
510 int len;
511 unsigned long pos;
512
513 ret = -EFAULT;
514 str = get_user_arg_ptr(argv, argc);
515 if (IS_ERR(str))
516 goto out;
517
518 len = strnlen_user(str, MAX_ARG_STRLEN);
519 if (!len)
520 goto out;
521
522 ret = -E2BIG;
523 if (!valid_arg_len(bprm, len))
524 goto out;
525
526 /* We're going to work our way backwords. */
527 pos = bprm->p;
528 str += len;
529 bprm->p -= len;
530
531 while (len > 0) {
532 int offset, bytes_to_copy;
533
534 if (fatal_signal_pending(current)) {
535 ret = -ERESTARTNOHAND;
536 goto out;
537 }
538 cond_resched();
539
540 offset = pos % PAGE_SIZE;
541 if (offset == 0)
542 offset = PAGE_SIZE;
543
544 bytes_to_copy = offset;
545 if (bytes_to_copy > len)
546 bytes_to_copy = len;
547
548 offset -= bytes_to_copy;
549 pos -= bytes_to_copy;
550 str -= bytes_to_copy;
551 len -= bytes_to_copy;
552
553 if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
554 struct page *page;
555
556 page = get_arg_page(bprm, pos, 1);
557 if (!page) {
558 ret = -E2BIG;
559 goto out;
560 }
561
562 if (kmapped_page) {
563 flush_kernel_dcache_page(kmapped_page);
564 kunmap(kmapped_page);
565 put_arg_page(kmapped_page);
566 }
567 kmapped_page = page;
568 kaddr = kmap(kmapped_page);
569 kpos = pos & PAGE_MASK;
570 flush_arg_page(bprm, kpos, kmapped_page);
571 }
572 if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
573 ret = -EFAULT;
574 goto out;
575 }
576 }
577 }
578 ret = 0;
579out:
580 if (kmapped_page) {
581 flush_kernel_dcache_page(kmapped_page);
582 kunmap(kmapped_page);
583 put_arg_page(kmapped_page);
584 }
585 return ret;
586}
587
588/*
589 * Like copy_strings, but get argv and its values from kernel memory.
590 */
591int copy_strings_kernel(int argc, const char *const *__argv,
592 struct linux_binprm *bprm)
593{
594 int r;
595 mm_segment_t oldfs = get_fs();
596 struct user_arg_ptr argv = {
597 .ptr.native = (const char __user *const __user *)__argv,
598 };
599
600 set_fs(KERNEL_DS);
601 r = copy_strings(argc, argv, bprm);
602 set_fs(oldfs);
603
604 return r;
605}
606EXPORT_SYMBOL(copy_strings_kernel);
607
608#ifdef CONFIG_MMU
609
610/*
611 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once
612 * the binfmt code determines where the new stack should reside, we shift it to
613 * its final location. The process proceeds as follows:
614 *
615 * 1) Use shift to calculate the new vma endpoints.
616 * 2) Extend vma to cover both the old and new ranges. This ensures the
617 * arguments passed to subsequent functions are consistent.
618 * 3) Move vma's page tables to the new range.
619 * 4) Free up any cleared pgd range.
620 * 5) Shrink the vma to cover only the new range.
621 */
622static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
623{
624 struct mm_struct *mm = vma->vm_mm;
625 unsigned long old_start = vma->vm_start;
626 unsigned long old_end = vma->vm_end;
627 unsigned long length = old_end - old_start;
628 unsigned long new_start = old_start - shift;
629 unsigned long new_end = old_end - shift;
630 struct mmu_gather tlb;
631
632 BUG_ON(new_start > new_end);
633
634 /*
635 * ensure there are no vmas between where we want to go
636 * and where we are
637 */
638 if (vma != find_vma(mm, new_start))
639 return -EFAULT;
640
641 /*
642 * cover the whole range: [new_start, old_end)
643 */
644 if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
645 return -ENOMEM;
646
647 /*
648 * move the page tables downwards, on failure we rely on
649 * process cleanup to remove whatever mess we made.
650 */
651 if (length != move_page_tables(vma, old_start,
652 vma, new_start, length, false))
653 return -ENOMEM;
654
655 lru_add_drain();
656 tlb_gather_mmu(&tlb, mm, old_start, old_end);
657 if (new_end > old_start) {
658 /*
659 * when the old and new regions overlap clear from new_end.
660 */
661 free_pgd_range(&tlb, new_end, old_end, new_end,
662 vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
663 } else {
664 /*
665 * otherwise, clean from old_start; this is done to not touch
666 * the address space in [new_end, old_start) some architectures
667 * have constraints on va-space that make this illegal (IA64) -
668 * for the others its just a little faster.
669 */
670 free_pgd_range(&tlb, old_start, old_end, new_end,
671 vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
672 }
673 tlb_finish_mmu(&tlb, old_start, old_end);
674
675 /*
676 * Shrink the vma to just the new range. Always succeeds.
677 */
678 vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
679
680 return 0;
681}
682
683/*
684 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
685 * the stack is optionally relocated, and some extra space is added.
686 */
687int setup_arg_pages(struct linux_binprm *bprm,
688 unsigned long stack_top,
689 int executable_stack)
690{
691 unsigned long ret;
692 unsigned long stack_shift;
693 struct mm_struct *mm = current->mm;
694 struct vm_area_struct *vma = bprm->vma;
695 struct vm_area_struct *prev = NULL;
696 unsigned long vm_flags;
697 unsigned long stack_base;
698 unsigned long stack_size;
699 unsigned long stack_expand;
700 unsigned long rlim_stack;
701
702#ifdef CONFIG_STACK_GROWSUP
703 /* Limit stack size */
704 stack_base = bprm->rlim_stack.rlim_max;
705 if (stack_base > STACK_SIZE_MAX)
706 stack_base = STACK_SIZE_MAX;
707
708 /* Add space for stack randomization. */
709 stack_base += (STACK_RND_MASK << PAGE_SHIFT);
710
711 /* Make sure we didn't let the argument array grow too large. */
712 if (vma->vm_end - vma->vm_start > stack_base)
713 return -ENOMEM;
714
715 stack_base = PAGE_ALIGN(stack_top - stack_base);
716
717 stack_shift = vma->vm_start - stack_base;
718 mm->arg_start = bprm->p - stack_shift;
719 bprm->p = vma->vm_end - stack_shift;
720#else
721 stack_top = arch_align_stack(stack_top);
722 stack_top = PAGE_ALIGN(stack_top);
723
724 if (unlikely(stack_top < mmap_min_addr) ||
725 unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
726 return -ENOMEM;
727
728 stack_shift = vma->vm_end - stack_top;
729
730 bprm->p -= stack_shift;
731 mm->arg_start = bprm->p;
732#endif
733
734 if (bprm->loader)
735 bprm->loader -= stack_shift;
736 bprm->exec -= stack_shift;
737
738 if (down_write_killable(&mm->mmap_sem))
739 return -EINTR;
740
741 vm_flags = VM_STACK_FLAGS;
742
743 /*
744 * Adjust stack execute permissions; explicitly enable for
745 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
746 * (arch default) otherwise.
747 */
748 if (unlikely(executable_stack == EXSTACK_ENABLE_X))
749 vm_flags |= VM_EXEC;
750 else if (executable_stack == EXSTACK_DISABLE_X)
751 vm_flags &= ~VM_EXEC;
752 vm_flags |= mm->def_flags;
753 vm_flags |= VM_STACK_INCOMPLETE_SETUP;
754
755 ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
756 vm_flags);
757 if (ret)
758 goto out_unlock;
759 BUG_ON(prev != vma);
760
761 /* Move stack pages down in memory. */
762 if (stack_shift) {
763 ret = shift_arg_pages(vma, stack_shift);
764 if (ret)
765 goto out_unlock;
766 }
767
768 /* mprotect_fixup is overkill to remove the temporary stack flags */
769 vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
770
771 stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
772 stack_size = vma->vm_end - vma->vm_start;
773 /*
774 * Align this down to a page boundary as expand_stack
775 * will align it up.
776 */
777 rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK;
778#ifdef CONFIG_STACK_GROWSUP
779 if (stack_size + stack_expand > rlim_stack)
780 stack_base = vma->vm_start + rlim_stack;
781 else
782 stack_base = vma->vm_end + stack_expand;
783#else
784 if (stack_size + stack_expand > rlim_stack)
785 stack_base = vma->vm_end - rlim_stack;
786 else
787 stack_base = vma->vm_start - stack_expand;
788#endif
789 current->mm->start_stack = bprm->p;
790 ret = expand_stack(vma, stack_base);
791 if (ret)
792 ret = -EFAULT;
793
794out_unlock:
795 up_write(&mm->mmap_sem);
796 return ret;
797}
798EXPORT_SYMBOL(setup_arg_pages);
799
800#else
801
802/*
803 * Transfer the program arguments and environment from the holding pages
804 * onto the stack. The provided stack pointer is adjusted accordingly.
805 */
806int transfer_args_to_stack(struct linux_binprm *bprm,
807 unsigned long *sp_location)
808{
809 unsigned long index, stop, sp;
810 int ret = 0;
811
812 stop = bprm->p >> PAGE_SHIFT;
813 sp = *sp_location;
814
815 for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
816 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
817 char *src = kmap(bprm->page[index]) + offset;
818 sp -= PAGE_SIZE - offset;
819 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
820 ret = -EFAULT;
821 kunmap(bprm->page[index]);
822 if (ret)
823 goto out;
824 }
825
826 *sp_location = sp;
827
828out:
829 return ret;
830}
831EXPORT_SYMBOL(transfer_args_to_stack);
832
833#endif /* CONFIG_MMU */
834
835static struct file *do_open_execat(int fd, struct filename *name, int flags)
836{
837 struct file *file;
838 int err;
839 struct open_flags open_exec_flags = {
840 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
841 .acc_mode = MAY_EXEC,
842 .intent = LOOKUP_OPEN,
843 .lookup_flags = LOOKUP_FOLLOW,
844 };
845
846 if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
847 return ERR_PTR(-EINVAL);
848 if (flags & AT_SYMLINK_NOFOLLOW)
849 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
850 if (flags & AT_EMPTY_PATH)
851 open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
852
853 file = do_filp_open(fd, name, &open_exec_flags);
854 if (IS_ERR(file))
855 goto out;
856
857 err = -EACCES;
858 if (!S_ISREG(file_inode(file)->i_mode))
859 goto exit;
860
861 if (path_noexec(&file->f_path))
862 goto exit;
863
864 err = deny_write_access(file);
865 if (err)
866 goto exit;
867
868 if (name->name[0] != '\0')
869 fsnotify_open(file);
870
871out:
872 return file;
873
874exit:
875 fput(file);
876 return ERR_PTR(err);
877}
878
879struct file *open_exec(const char *name)
880{
881 struct filename *filename = getname_kernel(name);
882 struct file *f = ERR_CAST(filename);
883
884 if (!IS_ERR(filename)) {
885 f = do_open_execat(AT_FDCWD, filename, 0);
886 putname(filename);
887 }
888 return f;
889}
890EXPORT_SYMBOL(open_exec);
891
892int kernel_read_file(struct file *file, void **buf, loff_t *size,
893 loff_t max_size, enum kernel_read_file_id id)
894{
895 loff_t i_size, pos;
896 ssize_t bytes = 0;
897 int ret;
898
899 if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
900 return -EINVAL;
901
902 ret = deny_write_access(file);
903 if (ret)
904 return ret;
905
906 ret = security_kernel_read_file(file, id);
907 if (ret)
908 goto out;
909
910 i_size = i_size_read(file_inode(file));
911 if (i_size <= 0) {
912 ret = -EINVAL;
913 goto out;
914 }
915 if (i_size > SIZE_MAX || (max_size > 0 && i_size > max_size)) {
916 ret = -EFBIG;
917 goto out;
918 }
919
920 if (id != READING_FIRMWARE_PREALLOC_BUFFER)
921 *buf = vmalloc(i_size);
922 if (!*buf) {
923 ret = -ENOMEM;
924 goto out;
925 }
926
927 pos = 0;
928 while (pos < i_size) {
929 bytes = kernel_read(file, *buf + pos, i_size - pos, &pos);
930 if (bytes < 0) {
931 ret = bytes;
932 goto out;
933 }
934
935 if (bytes == 0)
936 break;
937 }
938
939 if (pos != i_size) {
940 ret = -EIO;
941 goto out_free;
942 }
943
944 ret = security_kernel_post_read_file(file, *buf, i_size, id);
945 if (!ret)
946 *size = pos;
947
948out_free:
949 if (ret < 0) {
950 if (id != READING_FIRMWARE_PREALLOC_BUFFER) {
951 vfree(*buf);
952 *buf = NULL;
953 }
954 }
955
956out:
957 allow_write_access(file);
958 return ret;
959}
960EXPORT_SYMBOL_GPL(kernel_read_file);
961
962int kernel_read_file_from_path(const char *path, void **buf, loff_t *size,
963 loff_t max_size, enum kernel_read_file_id id)
964{
965 struct file *file;
966 int ret;
967
968 if (!path || !*path)
969 return -EINVAL;
970
971 file = filp_open(path, O_RDONLY, 0);
972 if (IS_ERR(file))
973 return PTR_ERR(file);
974
975 ret = kernel_read_file(file, buf, size, max_size, id);
976 fput(file);
977 return ret;
978}
979EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
980
981int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
982 enum kernel_read_file_id id)
983{
984 struct fd f = fdget(fd);
985 int ret = -EBADF;
986
987 if (!f.file)
988 goto out;
989
990 ret = kernel_read_file(f.file, buf, size, max_size, id);
991out:
992 fdput(f);
993 return ret;
994}
995EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);
996
997ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
998{
999 ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
1000 if (res > 0)
1001 flush_icache_range(addr, addr + len);
1002 return res;
1003}
1004EXPORT_SYMBOL(read_code);
1005
1006static int exec_mmap(struct mm_struct *mm)
1007{
1008 struct task_struct *tsk;
1009 struct mm_struct *old_mm, *active_mm;
1010
1011 /* Notify parent that we're no longer interested in the old VM */
1012 tsk = current;
1013 old_mm = current->mm;
1014 mm_release(tsk, old_mm);
1015
1016 if (old_mm) {
1017 sync_mm_rss(old_mm);
1018 /*
1019 * Make sure that if there is a core dump in progress
1020 * for the old mm, we get out and die instead of going
1021 * through with the exec. We must hold mmap_sem around
1022 * checking core_state and changing tsk->mm.
1023 */
1024 down_read(&old_mm->mmap_sem);
1025 if (unlikely(old_mm->core_state)) {
1026 up_read(&old_mm->mmap_sem);
1027 return -EINTR;
1028 }
1029 }
1030 task_lock(tsk);
1031 active_mm = tsk->active_mm;
1032 tsk->mm = mm;
1033 tsk->active_mm = mm;
1034 activate_mm(active_mm, mm);
1035 tsk->mm->vmacache_seqnum = 0;
1036 vmacache_flush(tsk);
1037 task_unlock(tsk);
1038 if (old_mm) {
1039 up_read(&old_mm->mmap_sem);
1040 BUG_ON(active_mm != old_mm);
1041 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
1042 mm_update_next_owner(old_mm);
1043 mmput(old_mm);
1044 return 0;
1045 }
1046 mmdrop(active_mm);
1047 return 0;
1048}
1049
1050/*
1051 * This function makes sure the current process has its own signal table,
1052 * so that flush_signal_handlers can later reset the handlers without
1053 * disturbing other processes. (Other processes might share the signal
1054 * table via the CLONE_SIGHAND option to clone().)
1055 */
1056static int de_thread(struct task_struct *tsk)
1057{
1058 struct signal_struct *sig = tsk->signal;
1059 struct sighand_struct *oldsighand = tsk->sighand;
1060 spinlock_t *lock = &oldsighand->siglock;
1061
1062 if (thread_group_empty(tsk))
1063 goto no_thread_group;
1064
1065 /*
1066 * Kill all other threads in the thread group.
1067 */
1068 spin_lock_irq(lock);
1069 if (signal_group_exit(sig)) {
1070 /*
1071 * Another group action in progress, just
1072 * return so that the signal is processed.
1073 */
1074 spin_unlock_irq(lock);
1075 return -EAGAIN;
1076 }
1077
1078 sig->group_exit_task = tsk;
1079 sig->notify_count = zap_other_threads(tsk);
1080 if (!thread_group_leader(tsk))
1081 sig->notify_count--;
1082
1083 while (sig->notify_count) {
1084 __set_current_state(TASK_KILLABLE);
1085 spin_unlock_irq(lock);
1086 schedule();
1087 if (unlikely(__fatal_signal_pending(tsk)))
1088 goto killed;
1089 spin_lock_irq(lock);
1090 }
1091 spin_unlock_irq(lock);
1092
1093 /*
1094 * At this point all other threads have exited, all we have to
1095 * do is to wait for the thread group leader to become inactive,
1096 * and to assume its PID:
1097 */
1098 if (!thread_group_leader(tsk)) {
1099 struct task_struct *leader = tsk->group_leader;
1100
1101 for (;;) {
1102 cgroup_threadgroup_change_begin(tsk);
1103 write_lock_irq(&tasklist_lock);
1104 /*
1105 * Do this under tasklist_lock to ensure that
1106 * exit_notify() can't miss ->group_exit_task
1107 */
1108 sig->notify_count = -1;
1109 if (likely(leader->exit_state))
1110 break;
1111 __set_current_state(TASK_KILLABLE);
1112 write_unlock_irq(&tasklist_lock);
1113 cgroup_threadgroup_change_end(tsk);
1114 schedule();
1115 if (unlikely(__fatal_signal_pending(tsk)))
1116 goto killed;
1117 }
1118
1119 /*
1120 * The only record we have of the real-time age of a
1121 * process, regardless of execs it's done, is start_time.
1122 * All the past CPU time is accumulated in signal_struct
1123 * from sister threads now dead. But in this non-leader
1124 * exec, nothing survives from the original leader thread,
1125 * whose birth marks the true age of this process now.
1126 * When we take on its identity by switching to its PID, we
1127 * also take its birthdate (always earlier than our own).
1128 */
1129 tsk->start_time = leader->start_time;
1130 tsk->real_start_time = leader->real_start_time;
1131
1132 BUG_ON(!same_thread_group(leader, tsk));
1133 BUG_ON(has_group_leader_pid(tsk));
1134 /*
1135 * An exec() starts a new thread group with the
1136 * TGID of the previous thread group. Rehash the
1137 * two threads with a switched PID, and release
1138 * the former thread group leader:
1139 */
1140
1141 /* Become a process group leader with the old leader's pid.
1142 * The old leader becomes a thread of the this thread group.
1143 * Note: The old leader also uses this pid until release_task
1144 * is called. Odd but simple and correct.
1145 */
1146 tsk->pid = leader->pid;
1147 change_pid(tsk, PIDTYPE_PID, task_pid(leader));
1148 transfer_pid(leader, tsk, PIDTYPE_TGID);
1149 transfer_pid(leader, tsk, PIDTYPE_PGID);
1150 transfer_pid(leader, tsk, PIDTYPE_SID);
1151
1152 list_replace_rcu(&leader->tasks, &tsk->tasks);
1153 list_replace_init(&leader->sibling, &tsk->sibling);
1154
1155 tsk->group_leader = tsk;
1156 leader->group_leader = tsk;
1157
1158 tsk->exit_signal = SIGCHLD;
1159 leader->exit_signal = -1;
1160
1161 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1162 leader->exit_state = EXIT_DEAD;
1163
1164 /*
1165 * We are going to release_task()->ptrace_unlink() silently,
1166 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1167 * the tracer wont't block again waiting for this thread.
1168 */
1169 if (unlikely(leader->ptrace))
1170 __wake_up_parent(leader, leader->parent);
1171 write_unlock_irq(&tasklist_lock);
1172 cgroup_threadgroup_change_end(tsk);
1173
1174 release_task(leader);
1175 }
1176
1177 sig->group_exit_task = NULL;
1178 sig->notify_count = 0;
1179
1180no_thread_group:
1181 /* we have changed execution domain */
1182 tsk->exit_signal = SIGCHLD;
1183
1184#ifdef CONFIG_POSIX_TIMERS
1185 exit_itimers(sig);
1186 flush_itimer_signals();
1187#endif
1188
1189 if (atomic_read(&oldsighand->count) != 1) {
1190 struct sighand_struct *newsighand;
1191 /*
1192 * This ->sighand is shared with the CLONE_SIGHAND
1193 * but not CLONE_THREAD task, switch to the new one.
1194 */
1195 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1196 if (!newsighand)
1197 return -ENOMEM;
1198
1199 atomic_set(&newsighand->count, 1);
1200 memcpy(newsighand->action, oldsighand->action,
1201 sizeof(newsighand->action));
1202
1203 write_lock_irq(&tasklist_lock);
1204 spin_lock(&oldsighand->siglock);
1205 rcu_assign_pointer(tsk->sighand, newsighand);
1206 spin_unlock(&oldsighand->siglock);
1207 write_unlock_irq(&tasklist_lock);
1208
1209 __cleanup_sighand(oldsighand);
1210 }
1211
1212 BUG_ON(!thread_group_leader(tsk));
1213 return 0;
1214
1215killed:
1216 /* protects against exit_notify() and __exit_signal() */
1217 read_lock(&tasklist_lock);
1218 sig->group_exit_task = NULL;
1219 sig->notify_count = 0;
1220 read_unlock(&tasklist_lock);
1221 return -EAGAIN;
1222}
1223
1224char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
1225{
1226 task_lock(tsk);
1227 strncpy(buf, tsk->comm, buf_size);
1228 task_unlock(tsk);
1229 return buf;
1230}
1231EXPORT_SYMBOL_GPL(__get_task_comm);
1232
1233/*
1234 * These functions flushes out all traces of the currently running executable
1235 * so that a new one can be started
1236 */
1237
1238void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1239{
1240 task_lock(tsk);
1241 trace_task_rename(tsk, buf);
1242 strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1243 task_unlock(tsk);
1244 perf_event_comm(tsk, exec);
1245}
1246
1247/*
1248 * Calling this is the point of no return. None of the failures will be
1249 * seen by userspace since either the process is already taking a fatal
1250 * signal (via de_thread() or coredump), or will have SEGV raised
1251 * (after exec_mmap()) by search_binary_handlers (see below).
1252 */
1253int flush_old_exec(struct linux_binprm * bprm)
1254{
1255 int retval;
1256
1257 /*
1258 * Make sure we have a private signal table and that
1259 * we are unassociated from the previous thread group.
1260 */
1261 retval = de_thread(current);
1262 if (retval)
1263 goto out;
1264
1265 /*
1266 * Must be called _before_ exec_mmap() as bprm->mm is
1267 * not visibile until then. This also enables the update
1268 * to be lockless.
1269 */
1270 set_mm_exe_file(bprm->mm, bprm->file);
1271
1272 /*
1273 * Release all of the old mmap stuff
1274 */
1275 acct_arg_size(bprm, 0);
1276 retval = exec_mmap(bprm->mm);
1277 if (retval)
1278 goto out;
1279
1280 /*
1281 * After clearing bprm->mm (to mark that current is using the
1282 * prepared mm now), we have nothing left of the original
1283 * process. If anything from here on returns an error, the check
1284 * in search_binary_handler() will SEGV current.
1285 */
1286 bprm->mm = NULL;
1287
1288 set_fs(USER_DS);
1289 current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
1290 PF_NOFREEZE | PF_NO_SETAFFINITY);
1291 flush_thread();
1292 current->personality &= ~bprm->per_clear;
1293
1294 /*
1295 * We have to apply CLOEXEC before we change whether the process is
1296 * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1297 * trying to access the should-be-closed file descriptors of a process
1298 * undergoing exec(2).
1299 */
1300 do_close_on_exec(current->files);
1301 return 0;
1302
1303out:
1304 return retval;
1305}
1306EXPORT_SYMBOL(flush_old_exec);
1307
1308void would_dump(struct linux_binprm *bprm, struct file *file)
1309{
1310 struct inode *inode = file_inode(file);
1311 if (inode_permission(inode, MAY_READ) < 0) {
1312 struct user_namespace *old, *user_ns;
1313 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1314
1315 /* Ensure mm->user_ns contains the executable */
1316 user_ns = old = bprm->mm->user_ns;
1317 while ((user_ns != &init_user_ns) &&
1318 !privileged_wrt_inode_uidgid(user_ns, inode))
1319 user_ns = user_ns->parent;
1320
1321 if (old != user_ns) {
1322 bprm->mm->user_ns = get_user_ns(user_ns);
1323 put_user_ns(old);
1324 }
1325 }
1326}
1327EXPORT_SYMBOL(would_dump);
1328
1329void setup_new_exec(struct linux_binprm * bprm)
1330{
1331 /*
1332 * Once here, prepare_binrpm() will not be called any more, so
1333 * the final state of setuid/setgid/fscaps can be merged into the
1334 * secureexec flag.
1335 */
1336 bprm->secureexec |= bprm->cap_elevated;
1337
1338 if (bprm->secureexec) {
1339 /* Make sure parent cannot signal privileged process. */
1340 current->pdeath_signal = 0;
1341
1342 /*
1343 * For secureexec, reset the stack limit to sane default to
1344 * avoid bad behavior from the prior rlimits. This has to
1345 * happen before arch_pick_mmap_layout(), which examines
1346 * RLIMIT_STACK, but after the point of no return to avoid
1347 * needing to clean up the change on failure.
1348 */
1349 if (bprm->rlim_stack.rlim_cur > _STK_LIM)
1350 bprm->rlim_stack.rlim_cur = _STK_LIM;
1351 }
1352
1353 arch_pick_mmap_layout(current->mm, &bprm->rlim_stack);
1354
1355 current->sas_ss_sp = current->sas_ss_size = 0;
1356
1357 /*
1358 * Figure out dumpability. Note that this checking only of current
1359 * is wrong, but userspace depends on it. This should be testing
1360 * bprm->secureexec instead.
1361 */
1362 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
1363 !(uid_eq(current_euid(), current_uid()) &&
1364 gid_eq(current_egid(), current_gid())))
1365 set_dumpable(current->mm, suid_dumpable);
1366 else
1367 set_dumpable(current->mm, SUID_DUMP_USER);
1368
1369 arch_setup_new_exec();
1370 perf_event_exec();
1371 __set_task_comm(current, kbasename(bprm->filename), true);
1372
1373 /* Set the new mm task size. We have to do that late because it may
1374 * depend on TIF_32BIT which is only updated in flush_thread() on
1375 * some architectures like powerpc
1376 */
1377 current->mm->task_size = TASK_SIZE;
1378
1379 /* An exec changes our domain. We are no longer part of the thread
1380 group */
1381 current->self_exec_id++;
1382 flush_signal_handlers(current, 0);
1383}
1384EXPORT_SYMBOL(setup_new_exec);
1385
1386/* Runs immediately before start_thread() takes over. */
1387void finalize_exec(struct linux_binprm *bprm)
1388{
1389 /* Store any stack rlimit changes before starting thread. */
1390 task_lock(current->group_leader);
1391 current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack;
1392 task_unlock(current->group_leader);
1393}
1394EXPORT_SYMBOL(finalize_exec);
1395
1396/*
1397 * Prepare credentials and lock ->cred_guard_mutex.
1398 * install_exec_creds() commits the new creds and drops the lock.
1399 * Or, if exec fails before, free_bprm() should release ->cred and
1400 * and unlock.
1401 */
1402int prepare_bprm_creds(struct linux_binprm *bprm)
1403{
1404 if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1405 return -ERESTARTNOINTR;
1406
1407 bprm->cred = prepare_exec_creds();
1408 if (likely(bprm->cred))
1409 return 0;
1410
1411 mutex_unlock(&current->signal->cred_guard_mutex);
1412 return -ENOMEM;
1413}
1414
1415static void free_bprm(struct linux_binprm *bprm)
1416{
1417 free_arg_pages(bprm);
1418 if (bprm->cred) {
1419 mutex_unlock(&current->signal->cred_guard_mutex);
1420 abort_creds(bprm->cred);
1421 }
1422 if (bprm->file) {
1423 allow_write_access(bprm->file);
1424 fput(bprm->file);
1425 }
1426 /* If a binfmt changed the interp, free it. */
1427 if (bprm->interp != bprm->filename)
1428 kfree(bprm->interp);
1429 kfree(bprm);
1430}
1431
1432int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
1433{
1434 /* If a binfmt changed the interp, free it first. */
1435 if (bprm->interp != bprm->filename)
1436 kfree(bprm->interp);
1437 bprm->interp = kstrdup(interp, GFP_KERNEL);
1438 if (!bprm->interp)
1439 return -ENOMEM;
1440 return 0;
1441}
1442EXPORT_SYMBOL(bprm_change_interp);
1443
1444/*
1445 * install the new credentials for this executable
1446 */
1447void install_exec_creds(struct linux_binprm *bprm)
1448{
1449 security_bprm_committing_creds(bprm);
1450
1451 commit_creds(bprm->cred);
1452 bprm->cred = NULL;
1453
1454 /*
1455 * Disable monitoring for regular users
1456 * when executing setuid binaries. Must
1457 * wait until new credentials are committed
1458 * by commit_creds() above
1459 */
1460 if (get_dumpable(current->mm) != SUID_DUMP_USER)
1461 perf_event_exit_task(current);
1462 /*
1463 * cred_guard_mutex must be held at least to this point to prevent
1464 * ptrace_attach() from altering our determination of the task's
1465 * credentials; any time after this it may be unlocked.
1466 */
1467 security_bprm_committed_creds(bprm);
1468 mutex_unlock(&current->signal->cred_guard_mutex);
1469}
1470EXPORT_SYMBOL(install_exec_creds);
1471
1472/*
1473 * determine how safe it is to execute the proposed program
1474 * - the caller must hold ->cred_guard_mutex to protect against
1475 * PTRACE_ATTACH or seccomp thread-sync
1476 */
1477static void check_unsafe_exec(struct linux_binprm *bprm)
1478{
1479 struct task_struct *p = current, *t;
1480 unsigned n_fs;
1481
1482 if (p->ptrace)
1483 bprm->unsafe |= LSM_UNSAFE_PTRACE;
1484
1485 /*
1486 * This isn't strictly necessary, but it makes it harder for LSMs to
1487 * mess up.
1488 */
1489 if (task_no_new_privs(current))
1490 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1491
1492 t = p;
1493 n_fs = 1;
1494 spin_lock(&p->fs->lock);
1495 rcu_read_lock();
1496 while_each_thread(p, t) {
1497 if (t->fs == p->fs)
1498 n_fs++;
1499 }
1500 rcu_read_unlock();
1501
1502 if (p->fs->users > n_fs)
1503 bprm->unsafe |= LSM_UNSAFE_SHARE;
1504 else
1505 p->fs->in_exec = 1;
1506 spin_unlock(&p->fs->lock);
1507}
1508
1509static void bprm_fill_uid(struct linux_binprm *bprm)
1510{
1511 struct inode *inode;
1512 unsigned int mode;
1513 kuid_t uid;
1514 kgid_t gid;
1515
1516 /*
1517 * Since this can be called multiple times (via prepare_binprm),
1518 * we must clear any previous work done when setting set[ug]id
1519 * bits from any earlier bprm->file uses (for example when run
1520 * first for a setuid script then again for its interpreter).
1521 */
1522 bprm->cred->euid = current_euid();
1523 bprm->cred->egid = current_egid();
1524
1525 if (!mnt_may_suid(bprm->file->f_path.mnt))
1526 return;
1527
1528 if (task_no_new_privs(current))
1529 return;
1530
1531 inode = bprm->file->f_path.dentry->d_inode;
1532 mode = READ_ONCE(inode->i_mode);
1533 if (!(mode & (S_ISUID|S_ISGID)))
1534 return;
1535
1536 /* Be careful if suid/sgid is set */
1537 inode_lock(inode);
1538
1539 /* reload atomically mode/uid/gid now that lock held */
1540 mode = inode->i_mode;
1541 uid = inode->i_uid;
1542 gid = inode->i_gid;
1543 inode_unlock(inode);
1544
1545 /* We ignore suid/sgid if there are no mappings for them in the ns */
1546 if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
1547 !kgid_has_mapping(bprm->cred->user_ns, gid))
1548 return;
1549
1550 if (mode & S_ISUID) {
1551 bprm->per_clear |= PER_CLEAR_ON_SETID;
1552 bprm->cred->euid = uid;
1553 }
1554
1555 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1556 bprm->per_clear |= PER_CLEAR_ON_SETID;
1557 bprm->cred->egid = gid;
1558 }
1559}
1560
1561/*
1562 * Fill the binprm structure from the inode.
1563 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1564 *
1565 * This may be called multiple times for binary chains (scripts for example).
1566 */
1567int prepare_binprm(struct linux_binprm *bprm)
1568{
1569 int retval;
1570 loff_t pos = 0;
1571
1572 bprm_fill_uid(bprm);
1573
1574 /* fill in binprm security blob */
1575 retval = security_bprm_set_creds(bprm);
1576 if (retval)
1577 return retval;
1578 bprm->called_set_creds = 1;
1579
1580 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1581 return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
1582}
1583
1584EXPORT_SYMBOL(prepare_binprm);
1585
1586/*
1587 * Arguments are '\0' separated strings found at the location bprm->p
1588 * points to; chop off the first by relocating brpm->p to right after
1589 * the first '\0' encountered.
1590 */
1591int remove_arg_zero(struct linux_binprm *bprm)
1592{
1593 int ret = 0;
1594 unsigned long offset;
1595 char *kaddr;
1596 struct page *page;
1597
1598 if (!bprm->argc)
1599 return 0;
1600
1601 do {
1602 offset = bprm->p & ~PAGE_MASK;
1603 page = get_arg_page(bprm, bprm->p, 0);
1604 if (!page) {
1605 ret = -EFAULT;
1606 goto out;
1607 }
1608 kaddr = kmap_atomic(page);
1609
1610 for (; offset < PAGE_SIZE && kaddr[offset];
1611 offset++, bprm->p++)
1612 ;
1613
1614 kunmap_atomic(kaddr);
1615 put_arg_page(page);
1616 } while (offset == PAGE_SIZE);
1617
1618 bprm->p++;
1619 bprm->argc--;
1620 ret = 0;
1621
1622out:
1623 return ret;
1624}
1625EXPORT_SYMBOL(remove_arg_zero);
1626
1627#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1628/*
1629 * cycle the list of binary formats handler, until one recognizes the image
1630 */
1631int search_binary_handler(struct linux_binprm *bprm)
1632{
1633 bool need_retry = IS_ENABLED(CONFIG_MODULES);
1634 struct linux_binfmt *fmt;
1635 int retval;
1636
1637 /* This allows 4 levels of binfmt rewrites before failing hard. */
1638 if (bprm->recursion_depth > 5)
1639 return -ELOOP;
1640
1641 retval = security_bprm_check(bprm);
1642 if (retval)
1643 return retval;
1644
1645 retval = -ENOENT;
1646 retry:
1647 read_lock(&binfmt_lock);
1648 list_for_each_entry(fmt, &formats, lh) {
1649 if (!try_module_get(fmt->module))
1650 continue;
1651 read_unlock(&binfmt_lock);
1652 bprm->recursion_depth++;
1653 retval = fmt->load_binary(bprm);
1654 read_lock(&binfmt_lock);
1655 put_binfmt(fmt);
1656 bprm->recursion_depth--;
1657 if (retval < 0 && !bprm->mm) {
1658 /* we got to flush_old_exec() and failed after it */
1659 read_unlock(&binfmt_lock);
1660 force_sigsegv(SIGSEGV, current);
1661 return retval;
1662 }
1663 if (retval != -ENOEXEC || !bprm->file) {
1664 read_unlock(&binfmt_lock);
1665 return retval;
1666 }
1667 }
1668 read_unlock(&binfmt_lock);
1669
1670 if (need_retry) {
1671 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1672 printable(bprm->buf[2]) && printable(bprm->buf[3]))
1673 return retval;
1674 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1675 return retval;
1676 need_retry = false;
1677 goto retry;
1678 }
1679
1680 return retval;
1681}
1682EXPORT_SYMBOL(search_binary_handler);
1683
1684static int exec_binprm(struct linux_binprm *bprm)
1685{
1686 pid_t old_pid, old_vpid;
1687 int ret;
1688
1689 /* Need to fetch pid before load_binary changes it */
1690 old_pid = current->pid;
1691 rcu_read_lock();
1692 old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1693 rcu_read_unlock();
1694
1695 ret = search_binary_handler(bprm);
1696 if (ret >= 0) {
1697 audit_bprm(bprm);
1698 trace_sched_process_exec(current, old_pid, bprm);
1699 ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1700 proc_exec_connector(current);
1701 }
1702
1703 return ret;
1704}
1705
1706/*
1707 * sys_execve() executes a new program.
1708 */
1709static int __do_execve_file(int fd, struct filename *filename,
1710 struct user_arg_ptr argv,
1711 struct user_arg_ptr envp,
1712 int flags, struct file *file)
1713{
1714 char *pathbuf = NULL;
1715 struct linux_binprm *bprm;
1716 struct files_struct *displaced;
1717 int retval;
1718
1719 if (IS_ERR(filename))
1720 return PTR_ERR(filename);
1721
1722 /*
1723 * We move the actual failure in case of RLIMIT_NPROC excess from
1724 * set*uid() to execve() because too many poorly written programs
1725 * don't check setuid() return code. Here we additionally recheck
1726 * whether NPROC limit is still exceeded.
1727 */
1728 if ((current->flags & PF_NPROC_EXCEEDED) &&
1729 atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
1730 retval = -EAGAIN;
1731 goto out_ret;
1732 }
1733
1734 /* We're below the limit (still or again), so we don't want to make
1735 * further execve() calls fail. */
1736 current->flags &= ~PF_NPROC_EXCEEDED;
1737
1738 retval = unshare_files(&displaced);
1739 if (retval)
1740 goto out_ret;
1741
1742 retval = -ENOMEM;
1743 bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1744 if (!bprm)
1745 goto out_files;
1746
1747 retval = prepare_bprm_creds(bprm);
1748 if (retval)
1749 goto out_free;
1750
1751 check_unsafe_exec(bprm);
1752 current->in_execve = 1;
1753
1754 if (!file)
1755 file = do_open_execat(fd, filename, flags);
1756 retval = PTR_ERR(file);
1757 if (IS_ERR(file))
1758 goto out_unmark;
1759
1760 sched_exec();
1761
1762 bprm->file = file;
1763 if (!filename) {
1764 bprm->filename = "none";
1765 } else if (fd == AT_FDCWD || filename->name[0] == '/') {
1766 bprm->filename = filename->name;
1767 } else {
1768 if (filename->name[0] == '\0')
1769 pathbuf = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd);
1770 else
1771 pathbuf = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s",
1772 fd, filename->name);
1773 if (!pathbuf) {
1774 retval = -ENOMEM;
1775 goto out_unmark;
1776 }
1777 /*
1778 * Record that a name derived from an O_CLOEXEC fd will be
1779 * inaccessible after exec. Relies on having exclusive access to
1780 * current->files (due to unshare_files above).
1781 */
1782 if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt)))
1783 bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1784 bprm->filename = pathbuf;
1785 }
1786 bprm->interp = bprm->filename;
1787
1788 retval = bprm_mm_init(bprm);
1789 if (retval)
1790 goto out_unmark;
1791
1792 bprm->argc = count(argv, MAX_ARG_STRINGS);
1793 if ((retval = bprm->argc) < 0)
1794 goto out;
1795
1796 bprm->envc = count(envp, MAX_ARG_STRINGS);
1797 if ((retval = bprm->envc) < 0)
1798 goto out;
1799
1800 retval = prepare_binprm(bprm);
1801 if (retval < 0)
1802 goto out;
1803
1804 retval = copy_strings_kernel(1, &bprm->filename, bprm);
1805 if (retval < 0)
1806 goto out;
1807
1808 bprm->exec = bprm->p;
1809 retval = copy_strings(bprm->envc, envp, bprm);
1810 if (retval < 0)
1811 goto out;
1812
1813 retval = copy_strings(bprm->argc, argv, bprm);
1814 if (retval < 0)
1815 goto out;
1816
1817 would_dump(bprm, bprm->file);
1818
1819 retval = exec_binprm(bprm);
1820 if (retval < 0)
1821 goto out;
1822
1823 /* execve succeeded */
1824 current->fs->in_exec = 0;
1825 current->in_execve = 0;
1826 membarrier_execve(current);
1827 rseq_execve(current);
1828 acct_update_integrals(current);
1829 task_numa_free(current);
1830 free_bprm(bprm);
1831 kfree(pathbuf);
1832 if (filename)
1833 putname(filename);
1834 if (displaced)
1835 put_files_struct(displaced);
1836 return retval;
1837
1838out:
1839 if (bprm->mm) {
1840 acct_arg_size(bprm, 0);
1841 mmput(bprm->mm);
1842 }
1843
1844out_unmark:
1845 current->fs->in_exec = 0;
1846 current->in_execve = 0;
1847
1848out_free:
1849 free_bprm(bprm);
1850 kfree(pathbuf);
1851
1852out_files:
1853 if (displaced)
1854 reset_files_struct(displaced);
1855out_ret:
1856 if (filename)
1857 putname(filename);
1858 return retval;
1859}
1860
1861static int do_execveat_common(int fd, struct filename *filename,
1862 struct user_arg_ptr argv,
1863 struct user_arg_ptr envp,
1864 int flags)
1865{
1866 return __do_execve_file(fd, filename, argv, envp, flags, NULL);
1867}
1868
1869int do_execve_file(struct file *file, void *__argv, void *__envp)
1870{
1871 struct user_arg_ptr argv = { .ptr.native = __argv };
1872 struct user_arg_ptr envp = { .ptr.native = __envp };
1873
1874 return __do_execve_file(AT_FDCWD, NULL, argv, envp, 0, file);
1875}
1876
1877int do_execve(struct filename *filename,
1878 const char __user *const __user *__argv,
1879 const char __user *const __user *__envp)
1880{
1881 struct user_arg_ptr argv = { .ptr.native = __argv };
1882 struct user_arg_ptr envp = { .ptr.native = __envp };
1883 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1884}
1885
1886int do_execveat(int fd, struct filename *filename,
1887 const char __user *const __user *__argv,
1888 const char __user *const __user *__envp,
1889 int flags)
1890{
1891 struct user_arg_ptr argv = { .ptr.native = __argv };
1892 struct user_arg_ptr envp = { .ptr.native = __envp };
1893
1894 return do_execveat_common(fd, filename, argv, envp, flags);
1895}
1896
1897#ifdef CONFIG_COMPAT
1898static int compat_do_execve(struct filename *filename,
1899 const compat_uptr_t __user *__argv,
1900 const compat_uptr_t __user *__envp)
1901{
1902 struct user_arg_ptr argv = {
1903 .is_compat = true,
1904 .ptr.compat = __argv,
1905 };
1906 struct user_arg_ptr envp = {
1907 .is_compat = true,
1908 .ptr.compat = __envp,
1909 };
1910 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1911}
1912
1913static int compat_do_execveat(int fd, struct filename *filename,
1914 const compat_uptr_t __user *__argv,
1915 const compat_uptr_t __user *__envp,
1916 int flags)
1917{
1918 struct user_arg_ptr argv = {
1919 .is_compat = true,
1920 .ptr.compat = __argv,
1921 };
1922 struct user_arg_ptr envp = {
1923 .is_compat = true,
1924 .ptr.compat = __envp,
1925 };
1926 return do_execveat_common(fd, filename, argv, envp, flags);
1927}
1928#endif
1929
1930void set_binfmt(struct linux_binfmt *new)
1931{
1932 struct mm_struct *mm = current->mm;
1933
1934 if (mm->binfmt)
1935 module_put(mm->binfmt->module);
1936
1937 mm->binfmt = new;
1938 if (new)
1939 __module_get(new->module);
1940}
1941EXPORT_SYMBOL(set_binfmt);
1942
1943/*
1944 * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
1945 */
1946void set_dumpable(struct mm_struct *mm, int value)
1947{
1948 unsigned long old, new;
1949
1950 if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
1951 return;
1952
1953 do {
1954 old = READ_ONCE(mm->flags);
1955 new = (old & ~MMF_DUMPABLE_MASK) | value;
1956 } while (cmpxchg(&mm->flags, old, new) != old);
1957}
1958
1959SYSCALL_DEFINE3(execve,
1960 const char __user *, filename,
1961 const char __user *const __user *, argv,
1962 const char __user *const __user *, envp)
1963{
1964 return do_execve(getname(filename), argv, envp);
1965}
1966
1967SYSCALL_DEFINE5(execveat,
1968 int, fd, const char __user *, filename,
1969 const char __user *const __user *, argv,
1970 const char __user *const __user *, envp,
1971 int, flags)
1972{
1973 int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1974
1975 return do_execveat(fd,
1976 getname_flags(filename, lookup_flags, NULL),
1977 argv, envp, flags);
1978}
1979
1980#ifdef CONFIG_COMPAT
1981COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
1982 const compat_uptr_t __user *, argv,
1983 const compat_uptr_t __user *, envp)
1984{
1985 return compat_do_execve(getname(filename), argv, envp);
1986}
1987
1988COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
1989 const char __user *, filename,
1990 const compat_uptr_t __user *, argv,
1991 const compat_uptr_t __user *, envp,
1992 int, flags)
1993{
1994 int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1995
1996 return compat_do_execveat(fd,
1997 getname_flags(filename, lookup_flags, NULL),
1998 argv, envp, flags);
1999}
2000#endif