projects/linux·blob v2.6.32 · refs

1924 lines · 44.3 KiB

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/stat.h>
30#include <linux/fcntl.h>
31#include <linux/smp_lock.h>
32#include <linux/swap.h>
33#include <linux/string.h>
34#include <linux/init.h>
35#include <linux/pagemap.h>
36#include <linux/perf_event.h>
37#include <linux/highmem.h>
38#include <linux/spinlock.h>
39#include <linux/key.h>
40#include <linux/personality.h>
41#include <linux/binfmts.h>
42#include <linux/utsname.h>
43#include <linux/pid_namespace.h>
44#include <linux/module.h>
45#include <linux/namei.h>
46#include <linux/proc_fs.h>
47#include <linux/mount.h>
48#include <linux/security.h>
49#include <linux/ima.h>
50#include <linux/syscalls.h>
51#include <linux/tsacct_kern.h>
52#include <linux/cn_proc.h>
53#include <linux/audit.h>
54#include <linux/tracehook.h>
55#include <linux/kmod.h>
56#include <linux/fsnotify.h>
57#include <linux/fs_struct.h>
58#include <linux/pipe_fs_i.h>
59
60#include <asm/uaccess.h>
61#include <asm/mmu_context.h>
62#include <asm/tlb.h>
63#include "internal.h"
64
65int core_uses_pid;
66char core_pattern[CORENAME_MAX_SIZE] = "core";
67unsigned int core_pipe_limit;
68int suid_dumpable = 0;
69
70/* The maximal length of core_pattern is also specified in sysctl.c */
71
72static LIST_HEAD(formats);
73static DEFINE_RWLOCK(binfmt_lock);
74
75int __register_binfmt(struct linux_binfmt * fmt, int insert)
76{
77 if (!fmt)
78 return -EINVAL;
79 write_lock(&binfmt_lock);
80 insert ? list_add(&fmt->lh, &formats) :
81 list_add_tail(&fmt->lh, &formats);
82 write_unlock(&binfmt_lock);
83 return 0;
84}
85
86EXPORT_SYMBOL(__register_binfmt);
87
88void unregister_binfmt(struct linux_binfmt * fmt)
89{
90 write_lock(&binfmt_lock);
91 list_del(&fmt->lh);
92 write_unlock(&binfmt_lock);
93}
94
95EXPORT_SYMBOL(unregister_binfmt);
96
97static inline void put_binfmt(struct linux_binfmt * fmt)
98{
99 module_put(fmt->module);
100}
101
102/*
103 * Note that a shared library must be both readable and executable due to
104 * security reasons.
105 *
106 * Also note that we take the address to load from from the file itself.
107 */
108SYSCALL_DEFINE1(uselib, const char __user *, library)
109{
110 struct file *file;
111 char *tmp = getname(library);
112 int error = PTR_ERR(tmp);
113
114 if (IS_ERR(tmp))
115 goto out;
116
117 file = do_filp_open(AT_FDCWD, tmp,
118 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0,
119 MAY_READ | MAY_EXEC | MAY_OPEN);
120 putname(tmp);
121 error = PTR_ERR(file);
122 if (IS_ERR(file))
123 goto out;
124
125 error = -EINVAL;
126 if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
127 goto exit;
128
129 error = -EACCES;
130 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
131 goto exit;
132
133 fsnotify_open(file->f_path.dentry);
134
135 error = -ENOEXEC;
136 if(file->f_op) {
137 struct linux_binfmt * fmt;
138
139 read_lock(&binfmt_lock);
140 list_for_each_entry(fmt, &formats, lh) {
141 if (!fmt->load_shlib)
142 continue;
143 if (!try_module_get(fmt->module))
144 continue;
145 read_unlock(&binfmt_lock);
146 error = fmt->load_shlib(file);
147 read_lock(&binfmt_lock);
148 put_binfmt(fmt);
149 if (error != -ENOEXEC)
150 break;
151 }
152 read_unlock(&binfmt_lock);
153 }
154exit:
155 fput(file);
156out:
157 return error;
158}
159
160#ifdef CONFIG_MMU
161
162static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
163 int write)
164{
165 struct page *page;
166 int ret;
167
168#ifdef CONFIG_STACK_GROWSUP
169 if (write) {
170 ret = expand_stack_downwards(bprm->vma, pos);
171 if (ret < 0)
172 return NULL;
173 }
174#endif
175 ret = get_user_pages(current, bprm->mm, pos,
176 1, write, 1, &page, NULL);
177 if (ret <= 0)
178 return NULL;
179
180 if (write) {
181 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
182 struct rlimit *rlim;
183
184 /*
185 * We've historically supported up to 32 pages (ARG_MAX)
186 * of argument strings even with small stacks
187 */
188 if (size <= ARG_MAX)
189 return page;
190
191 /*
192 * Limit to 1/4-th the stack size for the argv+env strings.
193 * This ensures that:
194 * - the remaining binfmt code will not run out of stack space,
195 * - the program will have a reasonable amount of stack left
196 * to work from.
197 */
198 rlim = current->signal->rlim;
199 if (size > rlim[RLIMIT_STACK].rlim_cur / 4) {
200 put_page(page);
201 return NULL;
202 }
203 }
204
205 return page;
206}
207
208static void put_arg_page(struct page *page)
209{
210 put_page(page);
211}
212
213static void free_arg_page(struct linux_binprm *bprm, int i)
214{
215}
216
217static void free_arg_pages(struct linux_binprm *bprm)
218{
219}
220
221static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
222 struct page *page)
223{
224 flush_cache_page(bprm->vma, pos, page_to_pfn(page));
225}
226
227static int __bprm_mm_init(struct linux_binprm *bprm)
228{
229 int err;
230 struct vm_area_struct *vma = NULL;
231 struct mm_struct *mm = bprm->mm;
232
233 bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
234 if (!vma)
235 return -ENOMEM;
236
237 down_write(&mm->mmap_sem);
238 vma->vm_mm = mm;
239
240 /*
241 * Place the stack at the largest stack address the architecture
242 * supports. Later, we'll move this to an appropriate place. We don't
243 * use STACK_TOP because that can depend on attributes which aren't
244 * configured yet.
245 */
246 vma->vm_end = STACK_TOP_MAX;
247 vma->vm_start = vma->vm_end - PAGE_SIZE;
248 vma->vm_flags = VM_STACK_FLAGS;
249 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
250 err = insert_vm_struct(mm, vma);
251 if (err)
252 goto err;
253
254 mm->stack_vm = mm->total_vm = 1;
255 up_write(&mm->mmap_sem);
256 bprm->p = vma->vm_end - sizeof(void *);
257 return 0;
258err:
259 up_write(&mm->mmap_sem);
260 bprm->vma = NULL;
261 kmem_cache_free(vm_area_cachep, vma);
262 return err;
263}
264
265static bool valid_arg_len(struct linux_binprm *bprm, long len)
266{
267 return len <= MAX_ARG_STRLEN;
268}
269
270#else
271
272static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
273 int write)
274{
275 struct page *page;
276
277 page = bprm->page[pos / PAGE_SIZE];
278 if (!page && write) {
279 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
280 if (!page)
281 return NULL;
282 bprm->page[pos / PAGE_SIZE] = page;
283 }
284
285 return page;
286}
287
288static void put_arg_page(struct page *page)
289{
290}
291
292static void free_arg_page(struct linux_binprm *bprm, int i)
293{
294 if (bprm->page[i]) {
295 __free_page(bprm->page[i]);
296 bprm->page[i] = NULL;
297 }
298}
299
300static void free_arg_pages(struct linux_binprm *bprm)
301{
302 int i;
303
304 for (i = 0; i < MAX_ARG_PAGES; i++)
305 free_arg_page(bprm, i);
306}
307
308static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
309 struct page *page)
310{
311}
312
313static int __bprm_mm_init(struct linux_binprm *bprm)
314{
315 bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
316 return 0;
317}
318
319static bool valid_arg_len(struct linux_binprm *bprm, long len)
320{
321 return len <= bprm->p;
322}
323
324#endif /* CONFIG_MMU */
325
326/*
327 * Create a new mm_struct and populate it with a temporary stack
328 * vm_area_struct. We don't have enough context at this point to set the stack
329 * flags, permissions, and offset, so we use temporary values. We'll update
330 * them later in setup_arg_pages().
331 */
332int bprm_mm_init(struct linux_binprm *bprm)
333{
334 int err;
335 struct mm_struct *mm = NULL;
336
337 bprm->mm = mm = mm_alloc();
338 err = -ENOMEM;
339 if (!mm)
340 goto err;
341
342 err = init_new_context(current, mm);
343 if (err)
344 goto err;
345
346 err = __bprm_mm_init(bprm);
347 if (err)
348 goto err;
349
350 return 0;
351
352err:
353 if (mm) {
354 bprm->mm = NULL;
355 mmdrop(mm);
356 }
357
358 return err;
359}
360
361/*
362 * count() counts the number of strings in array ARGV.
363 */
364static int count(char __user * __user * argv, int max)
365{
366 int i = 0;
367
368 if (argv != NULL) {
369 for (;;) {
370 char __user * p;
371
372 if (get_user(p, argv))
373 return -EFAULT;
374 if (!p)
375 break;
376 argv++;
377 if (i++ >= max)
378 return -E2BIG;
379 cond_resched();
380 }
381 }
382 return i;
383}
384
385/*
386 * 'copy_strings()' copies argument/environment strings from the old
387 * processes's memory to the new process's stack. The call to get_user_pages()
388 * ensures the destination page is created and not swapped out.
389 */
390static int copy_strings(int argc, char __user * __user * argv,
391 struct linux_binprm *bprm)
392{
393 struct page *kmapped_page = NULL;
394 char *kaddr = NULL;
395 unsigned long kpos = 0;
396 int ret;
397
398 while (argc-- > 0) {
399 char __user *str;
400 int len;
401 unsigned long pos;
402
403 if (get_user(str, argv+argc) ||
404 !(len = strnlen_user(str, MAX_ARG_STRLEN))) {
405 ret = -EFAULT;
406 goto out;
407 }
408
409 if (!valid_arg_len(bprm, len)) {
410 ret = -E2BIG;
411 goto out;
412 }
413
414 /* We're going to work our way backwords. */
415 pos = bprm->p;
416 str += len;
417 bprm->p -= len;
418
419 while (len > 0) {
420 int offset, bytes_to_copy;
421
422 offset = pos % PAGE_SIZE;
423 if (offset == 0)
424 offset = PAGE_SIZE;
425
426 bytes_to_copy = offset;
427 if (bytes_to_copy > len)
428 bytes_to_copy = len;
429
430 offset -= bytes_to_copy;
431 pos -= bytes_to_copy;
432 str -= bytes_to_copy;
433 len -= bytes_to_copy;
434
435 if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
436 struct page *page;
437
438 page = get_arg_page(bprm, pos, 1);
439 if (!page) {
440 ret = -E2BIG;
441 goto out;
442 }
443
444 if (kmapped_page) {
445 flush_kernel_dcache_page(kmapped_page);
446 kunmap(kmapped_page);
447 put_arg_page(kmapped_page);
448 }
449 kmapped_page = page;
450 kaddr = kmap(kmapped_page);
451 kpos = pos & PAGE_MASK;
452 flush_arg_page(bprm, kpos, kmapped_page);
453 }
454 if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
455 ret = -EFAULT;
456 goto out;
457 }
458 }
459 }
460 ret = 0;
461out:
462 if (kmapped_page) {
463 flush_kernel_dcache_page(kmapped_page);
464 kunmap(kmapped_page);
465 put_arg_page(kmapped_page);
466 }
467 return ret;
468}
469
470/*
471 * Like copy_strings, but get argv and its values from kernel memory.
472 */
473int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm)
474{
475 int r;
476 mm_segment_t oldfs = get_fs();
477 set_fs(KERNEL_DS);
478 r = copy_strings(argc, (char __user * __user *)argv, bprm);
479 set_fs(oldfs);
480 return r;
481}
482EXPORT_SYMBOL(copy_strings_kernel);
483
484#ifdef CONFIG_MMU
485
486/*
487 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once
488 * the binfmt code determines where the new stack should reside, we shift it to
489 * its final location. The process proceeds as follows:
490 *
491 * 1) Use shift to calculate the new vma endpoints.
492 * 2) Extend vma to cover both the old and new ranges. This ensures the
493 * arguments passed to subsequent functions are consistent.
494 * 3) Move vma's page tables to the new range.
495 * 4) Free up any cleared pgd range.
496 * 5) Shrink the vma to cover only the new range.
497 */
498static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
499{
500 struct mm_struct *mm = vma->vm_mm;
501 unsigned long old_start = vma->vm_start;
502 unsigned long old_end = vma->vm_end;
503 unsigned long length = old_end - old_start;
504 unsigned long new_start = old_start - shift;
505 unsigned long new_end = old_end - shift;
506 struct mmu_gather *tlb;
507
508 BUG_ON(new_start > new_end);
509
510 /*
511 * ensure there are no vmas between where we want to go
512 * and where we are
513 */
514 if (vma != find_vma(mm, new_start))
515 return -EFAULT;
516
517 /*
518 * cover the whole range: [new_start, old_end)
519 */
520 vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL);
521
522 /*
523 * move the page tables downwards, on failure we rely on
524 * process cleanup to remove whatever mess we made.
525 */
526 if (length != move_page_tables(vma, old_start,
527 vma, new_start, length))
528 return -ENOMEM;
529
530 lru_add_drain();
531 tlb = tlb_gather_mmu(mm, 0);
532 if (new_end > old_start) {
533 /*
534 * when the old and new regions overlap clear from new_end.
535 */
536 free_pgd_range(tlb, new_end, old_end, new_end,
537 vma->vm_next ? vma->vm_next->vm_start : 0);
538 } else {
539 /*
540 * otherwise, clean from old_start; this is done to not touch
541 * the address space in [new_end, old_start) some architectures
542 * have constraints on va-space that make this illegal (IA64) -
543 * for the others its just a little faster.
544 */
545 free_pgd_range(tlb, old_start, old_end, new_end,
546 vma->vm_next ? vma->vm_next->vm_start : 0);
547 }
548 tlb_finish_mmu(tlb, new_end, old_end);
549
550 /*
551 * shrink the vma to just the new range.
552 */
553 vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
554
555 return 0;
556}
557
558#define EXTRA_STACK_VM_PAGES 20 /* random */
559
560/*
561 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
562 * the stack is optionally relocated, and some extra space is added.
563 */
564int setup_arg_pages(struct linux_binprm *bprm,
565 unsigned long stack_top,
566 int executable_stack)
567{
568 unsigned long ret;
569 unsigned long stack_shift;
570 struct mm_struct *mm = current->mm;
571 struct vm_area_struct *vma = bprm->vma;
572 struct vm_area_struct *prev = NULL;
573 unsigned long vm_flags;
574 unsigned long stack_base;
575
576#ifdef CONFIG_STACK_GROWSUP
577 /* Limit stack size to 1GB */
578 stack_base = current->signal->rlim[RLIMIT_STACK].rlim_max;
579 if (stack_base > (1 << 30))
580 stack_base = 1 << 30;
581
582 /* Make sure we didn't let the argument array grow too large. */
583 if (vma->vm_end - vma->vm_start > stack_base)
584 return -ENOMEM;
585
586 stack_base = PAGE_ALIGN(stack_top - stack_base);
587
588 stack_shift = vma->vm_start - stack_base;
589 mm->arg_start = bprm->p - stack_shift;
590 bprm->p = vma->vm_end - stack_shift;
591#else
592 stack_top = arch_align_stack(stack_top);
593 stack_top = PAGE_ALIGN(stack_top);
594 stack_shift = vma->vm_end - stack_top;
595
596 bprm->p -= stack_shift;
597 mm->arg_start = bprm->p;
598#endif
599
600 if (bprm->loader)
601 bprm->loader -= stack_shift;
602 bprm->exec -= stack_shift;
603
604 down_write(&mm->mmap_sem);
605 vm_flags = VM_STACK_FLAGS;
606
607 /*
608 * Adjust stack execute permissions; explicitly enable for
609 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
610 * (arch default) otherwise.
611 */
612 if (unlikely(executable_stack == EXSTACK_ENABLE_X))
613 vm_flags |= VM_EXEC;
614 else if (executable_stack == EXSTACK_DISABLE_X)
615 vm_flags &= ~VM_EXEC;
616 vm_flags |= mm->def_flags;
617
618 ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
619 vm_flags);
620 if (ret)
621 goto out_unlock;
622 BUG_ON(prev != vma);
623
624 /* Move stack pages down in memory. */
625 if (stack_shift) {
626 ret = shift_arg_pages(vma, stack_shift);
627 if (ret)
628 goto out_unlock;
629 }
630
631#ifdef CONFIG_STACK_GROWSUP
632 stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE;
633#else
634 stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE;
635#endif
636 ret = expand_stack(vma, stack_base);
637 if (ret)
638 ret = -EFAULT;
639
640out_unlock:
641 up_write(&mm->mmap_sem);
642 return ret;
643}
644EXPORT_SYMBOL(setup_arg_pages);
645
646#endif /* CONFIG_MMU */
647
648struct file *open_exec(const char *name)
649{
650 struct file *file;
651 int err;
652
653 file = do_filp_open(AT_FDCWD, name,
654 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0,
655 MAY_EXEC | MAY_OPEN);
656 if (IS_ERR(file))
657 goto out;
658
659 err = -EACCES;
660 if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
661 goto exit;
662
663 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
664 goto exit;
665
666 fsnotify_open(file->f_path.dentry);
667
668 err = deny_write_access(file);
669 if (err)
670 goto exit;
671
672out:
673 return file;
674
675exit:
676 fput(file);
677 return ERR_PTR(err);
678}
679EXPORT_SYMBOL(open_exec);
680
681int kernel_read(struct file *file, loff_t offset,
682 char *addr, unsigned long count)
683{
684 mm_segment_t old_fs;
685 loff_t pos = offset;
686 int result;
687
688 old_fs = get_fs();
689 set_fs(get_ds());
690 /* The cast to a user pointer is valid due to the set_fs() */
691 result = vfs_read(file, (void __user *)addr, count, &pos);
692 set_fs(old_fs);
693 return result;
694}
695
696EXPORT_SYMBOL(kernel_read);
697
698static int exec_mmap(struct mm_struct *mm)
699{
700 struct task_struct *tsk;
701 struct mm_struct * old_mm, *active_mm;
702
703 /* Notify parent that we're no longer interested in the old VM */
704 tsk = current;
705 old_mm = current->mm;
706 mm_release(tsk, old_mm);
707
708 if (old_mm) {
709 /*
710 * Make sure that if there is a core dump in progress
711 * for the old mm, we get out and die instead of going
712 * through with the exec. We must hold mmap_sem around
713 * checking core_state and changing tsk->mm.
714 */
715 down_read(&old_mm->mmap_sem);
716 if (unlikely(old_mm->core_state)) {
717 up_read(&old_mm->mmap_sem);
718 return -EINTR;
719 }
720 }
721 task_lock(tsk);
722 active_mm = tsk->active_mm;
723 tsk->mm = mm;
724 tsk->active_mm = mm;
725 activate_mm(active_mm, mm);
726 task_unlock(tsk);
727 arch_pick_mmap_layout(mm);
728 if (old_mm) {
729 up_read(&old_mm->mmap_sem);
730 BUG_ON(active_mm != old_mm);
731 mm_update_next_owner(old_mm);
732 mmput(old_mm);
733 return 0;
734 }
735 mmdrop(active_mm);
736 return 0;
737}
738
739/*
740 * This function makes sure the current process has its own signal table,
741 * so that flush_signal_handlers can later reset the handlers without
742 * disturbing other processes. (Other processes might share the signal
743 * table via the CLONE_SIGHAND option to clone().)
744 */
745static int de_thread(struct task_struct *tsk)
746{
747 struct signal_struct *sig = tsk->signal;
748 struct sighand_struct *oldsighand = tsk->sighand;
749 spinlock_t *lock = &oldsighand->siglock;
750 int count;
751
752 if (thread_group_empty(tsk))
753 goto no_thread_group;
754
755 /*
756 * Kill all other threads in the thread group.
757 */
758 spin_lock_irq(lock);
759 if (signal_group_exit(sig)) {
760 /*
761 * Another group action in progress, just
762 * return so that the signal is processed.
763 */
764 spin_unlock_irq(lock);
765 return -EAGAIN;
766 }
767 sig->group_exit_task = tsk;
768 zap_other_threads(tsk);
769
770 /* Account for the thread group leader hanging around: */
771 count = thread_group_leader(tsk) ? 1 : 2;
772 sig->notify_count = count;
773 while (atomic_read(&sig->count) > count) {
774 __set_current_state(TASK_UNINTERRUPTIBLE);
775 spin_unlock_irq(lock);
776 schedule();
777 spin_lock_irq(lock);
778 }
779 spin_unlock_irq(lock);
780
781 /*
782 * At this point all other threads have exited, all we have to
783 * do is to wait for the thread group leader to become inactive,
784 * and to assume its PID:
785 */
786 if (!thread_group_leader(tsk)) {
787 struct task_struct *leader = tsk->group_leader;
788
789 sig->notify_count = -1; /* for exit_notify() */
790 for (;;) {
791 write_lock_irq(&tasklist_lock);
792 if (likely(leader->exit_state))
793 break;
794 __set_current_state(TASK_UNINTERRUPTIBLE);
795 write_unlock_irq(&tasklist_lock);
796 schedule();
797 }
798
799 /*
800 * The only record we have of the real-time age of a
801 * process, regardless of execs it's done, is start_time.
802 * All the past CPU time is accumulated in signal_struct
803 * from sister threads now dead. But in this non-leader
804 * exec, nothing survives from the original leader thread,
805 * whose birth marks the true age of this process now.
806 * When we take on its identity by switching to its PID, we
807 * also take its birthdate (always earlier than our own).
808 */
809 tsk->start_time = leader->start_time;
810
811 BUG_ON(!same_thread_group(leader, tsk));
812 BUG_ON(has_group_leader_pid(tsk));
813 /*
814 * An exec() starts a new thread group with the
815 * TGID of the previous thread group. Rehash the
816 * two threads with a switched PID, and release
817 * the former thread group leader:
818 */
819
820 /* Become a process group leader with the old leader's pid.
821 * The old leader becomes a thread of the this thread group.
822 * Note: The old leader also uses this pid until release_task
823 * is called. Odd but simple and correct.
824 */
825 detach_pid(tsk, PIDTYPE_PID);
826 tsk->pid = leader->pid;
827 attach_pid(tsk, PIDTYPE_PID, task_pid(leader));
828 transfer_pid(leader, tsk, PIDTYPE_PGID);
829 transfer_pid(leader, tsk, PIDTYPE_SID);
830 list_replace_rcu(&leader->tasks, &tsk->tasks);
831
832 tsk->group_leader = tsk;
833 leader->group_leader = tsk;
834
835 tsk->exit_signal = SIGCHLD;
836
837 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
838 leader->exit_state = EXIT_DEAD;
839 write_unlock_irq(&tasklist_lock);
840
841 release_task(leader);
842 }
843
844 sig->group_exit_task = NULL;
845 sig->notify_count = 0;
846
847no_thread_group:
848 if (current->mm)
849 setmax_mm_hiwater_rss(&sig->maxrss, current->mm);
850
851 exit_itimers(sig);
852 flush_itimer_signals();
853
854 if (atomic_read(&oldsighand->count) != 1) {
855 struct sighand_struct *newsighand;
856 /*
857 * This ->sighand is shared with the CLONE_SIGHAND
858 * but not CLONE_THREAD task, switch to the new one.
859 */
860 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
861 if (!newsighand)
862 return -ENOMEM;
863
864 atomic_set(&newsighand->count, 1);
865 memcpy(newsighand->action, oldsighand->action,
866 sizeof(newsighand->action));
867
868 write_lock_irq(&tasklist_lock);
869 spin_lock(&oldsighand->siglock);
870 rcu_assign_pointer(tsk->sighand, newsighand);
871 spin_unlock(&oldsighand->siglock);
872 write_unlock_irq(&tasklist_lock);
873
874 __cleanup_sighand(oldsighand);
875 }
876
877 BUG_ON(!thread_group_leader(tsk));
878 return 0;
879}
880
881/*
882 * These functions flushes out all traces of the currently running executable
883 * so that a new one can be started
884 */
885static void flush_old_files(struct files_struct * files)
886{
887 long j = -1;
888 struct fdtable *fdt;
889
890 spin_lock(&files->file_lock);
891 for (;;) {
892 unsigned long set, i;
893
894 j++;
895 i = j * __NFDBITS;
896 fdt = files_fdtable(files);
897 if (i >= fdt->max_fds)
898 break;
899 set = fdt->close_on_exec->fds_bits[j];
900 if (!set)
901 continue;
902 fdt->close_on_exec->fds_bits[j] = 0;
903 spin_unlock(&files->file_lock);
904 for ( ; set ; i++,set >>= 1) {
905 if (set & 1) {
906 sys_close(i);
907 }
908 }
909 spin_lock(&files->file_lock);
910
911 }
912 spin_unlock(&files->file_lock);
913}
914
915char *get_task_comm(char *buf, struct task_struct *tsk)
916{
917 /* buf must be at least sizeof(tsk->comm) in size */
918 task_lock(tsk);
919 strncpy(buf, tsk->comm, sizeof(tsk->comm));
920 task_unlock(tsk);
921 return buf;
922}
923
924void set_task_comm(struct task_struct *tsk, char *buf)
925{
926 task_lock(tsk);
927 strlcpy(tsk->comm, buf, sizeof(tsk->comm));
928 task_unlock(tsk);
929 perf_event_comm(tsk);
930}
931
932int flush_old_exec(struct linux_binprm * bprm)
933{
934 char * name;
935 int i, ch, retval;
936 char tcomm[sizeof(current->comm)];
937
938 /*
939 * Make sure we have a private signal table and that
940 * we are unassociated from the previous thread group.
941 */
942 retval = de_thread(current);
943 if (retval)
944 goto out;
945
946 set_mm_exe_file(bprm->mm, bprm->file);
947
948 /*
949 * Release all of the old mmap stuff
950 */
951 retval = exec_mmap(bprm->mm);
952 if (retval)
953 goto out;
954
955 bprm->mm = NULL; /* We're using it now */
956
957 /* This is the point of no return */
958 current->sas_ss_sp = current->sas_ss_size = 0;
959
960 if (current_euid() == current_uid() && current_egid() == current_gid())
961 set_dumpable(current->mm, 1);
962 else
963 set_dumpable(current->mm, suid_dumpable);
964
965 name = bprm->filename;
966
967 /* Copies the binary name from after last slash */
968 for (i=0; (ch = *(name++)) != '\0';) {
969 if (ch == '/')
970 i = 0; /* overwrite what we wrote */
971 else
972 if (i < (sizeof(tcomm) - 1))
973 tcomm[i++] = ch;
974 }
975 tcomm[i] = '\0';
976 set_task_comm(current, tcomm);
977
978 current->flags &= ~PF_RANDOMIZE;
979 flush_thread();
980
981 /* Set the new mm task size. We have to do that late because it may
982 * depend on TIF_32BIT which is only updated in flush_thread() on
983 * some architectures like powerpc
984 */
985 current->mm->task_size = TASK_SIZE;
986
987 /* install the new credentials */
988 if (bprm->cred->uid != current_euid() ||
989 bprm->cred->gid != current_egid()) {
990 current->pdeath_signal = 0;
991 } else if (file_permission(bprm->file, MAY_READ) ||
992 bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) {
993 set_dumpable(current->mm, suid_dumpable);
994 }
995
996 current->personality &= ~bprm->per_clear;
997
998 /*
999 * Flush performance counters when crossing a
1000 * security domain:
1001 */
1002 if (!get_dumpable(current->mm))
1003 perf_event_exit_task(current);
1004
1005 /* An exec changes our domain. We are no longer part of the thread
1006 group */
1007
1008 current->self_exec_id++;
1009
1010 flush_signal_handlers(current, 0);
1011 flush_old_files(current->files);
1012
1013 return 0;
1014
1015out:
1016 return retval;
1017}
1018
1019EXPORT_SYMBOL(flush_old_exec);
1020
1021/*
1022 * Prepare credentials and lock ->cred_guard_mutex.
1023 * install_exec_creds() commits the new creds and drops the lock.
1024 * Or, if exec fails before, free_bprm() should release ->cred and
1025 * and unlock.
1026 */
1027int prepare_bprm_creds(struct linux_binprm *bprm)
1028{
1029 if (mutex_lock_interruptible(&current->cred_guard_mutex))
1030 return -ERESTARTNOINTR;
1031
1032 bprm->cred = prepare_exec_creds();
1033 if (likely(bprm->cred))
1034 return 0;
1035
1036 mutex_unlock(&current->cred_guard_mutex);
1037 return -ENOMEM;
1038}
1039
1040void free_bprm(struct linux_binprm *bprm)
1041{
1042 free_arg_pages(bprm);
1043 if (bprm->cred) {
1044 mutex_unlock(&current->cred_guard_mutex);
1045 abort_creds(bprm->cred);
1046 }
1047 kfree(bprm);
1048}
1049
1050/*
1051 * install the new credentials for this executable
1052 */
1053void install_exec_creds(struct linux_binprm *bprm)
1054{
1055 security_bprm_committing_creds(bprm);
1056
1057 commit_creds(bprm->cred);
1058 bprm->cred = NULL;
1059 /*
1060 * cred_guard_mutex must be held at least to this point to prevent
1061 * ptrace_attach() from altering our determination of the task's
1062 * credentials; any time after this it may be unlocked.
1063 */
1064 security_bprm_committed_creds(bprm);
1065 mutex_unlock(&current->cred_guard_mutex);
1066}
1067EXPORT_SYMBOL(install_exec_creds);
1068
1069/*
1070 * determine how safe it is to execute the proposed program
1071 * - the caller must hold current->cred_guard_mutex to protect against
1072 * PTRACE_ATTACH
1073 */
1074int check_unsafe_exec(struct linux_binprm *bprm)
1075{
1076 struct task_struct *p = current, *t;
1077 unsigned n_fs;
1078 int res = 0;
1079
1080 bprm->unsafe = tracehook_unsafe_exec(p);
1081
1082 n_fs = 1;
1083 write_lock(&p->fs->lock);
1084 rcu_read_lock();
1085 for (t = next_thread(p); t != p; t = next_thread(t)) {
1086 if (t->fs == p->fs)
1087 n_fs++;
1088 }
1089 rcu_read_unlock();
1090
1091 if (p->fs->users > n_fs) {
1092 bprm->unsafe |= LSM_UNSAFE_SHARE;
1093 } else {
1094 res = -EAGAIN;
1095 if (!p->fs->in_exec) {
1096 p->fs->in_exec = 1;
1097 res = 1;
1098 }
1099 }
1100 write_unlock(&p->fs->lock);
1101
1102 return res;
1103}
1104
1105/*
1106 * Fill the binprm structure from the inode.
1107 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1108 *
1109 * This may be called multiple times for binary chains (scripts for example).
1110 */
1111int prepare_binprm(struct linux_binprm *bprm)
1112{
1113 umode_t mode;
1114 struct inode * inode = bprm->file->f_path.dentry->d_inode;
1115 int retval;
1116
1117 mode = inode->i_mode;
1118 if (bprm->file->f_op == NULL)
1119 return -EACCES;
1120
1121 /* clear any previous set[ug]id data from a previous binary */
1122 bprm->cred->euid = current_euid();
1123 bprm->cred->egid = current_egid();
1124
1125 if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
1126 /* Set-uid? */
1127 if (mode & S_ISUID) {
1128 bprm->per_clear |= PER_CLEAR_ON_SETID;
1129 bprm->cred->euid = inode->i_uid;
1130 }
1131
1132 /* Set-gid? */
1133 /*
1134 * If setgid is set but no group execute bit then this
1135 * is a candidate for mandatory locking, not a setgid
1136 * executable.
1137 */
1138 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1139 bprm->per_clear |= PER_CLEAR_ON_SETID;
1140 bprm->cred->egid = inode->i_gid;
1141 }
1142 }
1143
1144 /* fill in binprm security blob */
1145 retval = security_bprm_set_creds(bprm);
1146 if (retval)
1147 return retval;
1148 bprm->cred_prepared = 1;
1149
1150 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1151 return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1152}
1153
1154EXPORT_SYMBOL(prepare_binprm);
1155
1156/*
1157 * Arguments are '\0' separated strings found at the location bprm->p
1158 * points to; chop off the first by relocating brpm->p to right after
1159 * the first '\0' encountered.
1160 */
1161int remove_arg_zero(struct linux_binprm *bprm)
1162{
1163 int ret = 0;
1164 unsigned long offset;
1165 char *kaddr;
1166 struct page *page;
1167
1168 if (!bprm->argc)
1169 return 0;
1170
1171 do {
1172 offset = bprm->p & ~PAGE_MASK;
1173 page = get_arg_page(bprm, bprm->p, 0);
1174 if (!page) {
1175 ret = -EFAULT;
1176 goto out;
1177 }
1178 kaddr = kmap_atomic(page, KM_USER0);
1179
1180 for (; offset < PAGE_SIZE && kaddr[offset];
1181 offset++, bprm->p++)
1182 ;
1183
1184 kunmap_atomic(kaddr, KM_USER0);
1185 put_arg_page(page);
1186
1187 if (offset == PAGE_SIZE)
1188 free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1189 } while (offset == PAGE_SIZE);
1190
1191 bprm->p++;
1192 bprm->argc--;
1193 ret = 0;
1194
1195out:
1196 return ret;
1197}
1198EXPORT_SYMBOL(remove_arg_zero);
1199
1200/*
1201 * cycle the list of binary formats handler, until one recognizes the image
1202 */
1203int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1204{
1205 unsigned int depth = bprm->recursion_depth;
1206 int try,retval;
1207 struct linux_binfmt *fmt;
1208
1209 retval = security_bprm_check(bprm);
1210 if (retval)
1211 return retval;
1212 retval = ima_bprm_check(bprm);
1213 if (retval)
1214 return retval;
1215
1216 /* kernel module loader fixup */
1217 /* so we don't try to load run modprobe in kernel space. */
1218 set_fs(USER_DS);
1219
1220 retval = audit_bprm(bprm);
1221 if (retval)
1222 return retval;
1223
1224 retval = -ENOENT;
1225 for (try=0; try<2; try++) {
1226 read_lock(&binfmt_lock);
1227 list_for_each_entry(fmt, &formats, lh) {
1228 int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1229 if (!fn)
1230 continue;
1231 if (!try_module_get(fmt->module))
1232 continue;
1233 read_unlock(&binfmt_lock);
1234 retval = fn(bprm, regs);
1235 /*
1236 * Restore the depth counter to its starting value
1237 * in this call, so we don't have to rely on every
1238 * load_binary function to restore it on return.
1239 */
1240 bprm->recursion_depth = depth;
1241 if (retval >= 0) {
1242 if (depth == 0)
1243 tracehook_report_exec(fmt, bprm, regs);
1244 put_binfmt(fmt);
1245 allow_write_access(bprm->file);
1246 if (bprm->file)
1247 fput(bprm->file);
1248 bprm->file = NULL;
1249 current->did_exec = 1;
1250 proc_exec_connector(current);
1251 return retval;
1252 }
1253 read_lock(&binfmt_lock);
1254 put_binfmt(fmt);
1255 if (retval != -ENOEXEC || bprm->mm == NULL)
1256 break;
1257 if (!bprm->file) {
1258 read_unlock(&binfmt_lock);
1259 return retval;
1260 }
1261 }
1262 read_unlock(&binfmt_lock);
1263 if (retval != -ENOEXEC || bprm->mm == NULL) {
1264 break;
1265#ifdef CONFIG_MODULES
1266 } else {
1267#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1268 if (printable(bprm->buf[0]) &&
1269 printable(bprm->buf[1]) &&
1270 printable(bprm->buf[2]) &&
1271 printable(bprm->buf[3]))
1272 break; /* -ENOEXEC */
1273 request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1274#endif
1275 }
1276 }
1277 return retval;
1278}
1279
1280EXPORT_SYMBOL(search_binary_handler);
1281
1282/*
1283 * sys_execve() executes a new program.
1284 */
1285int do_execve(char * filename,
1286 char __user *__user *argv,
1287 char __user *__user *envp,
1288 struct pt_regs * regs)
1289{
1290 struct linux_binprm *bprm;
1291 struct file *file;
1292 struct files_struct *displaced;
1293 bool clear_in_exec;
1294 int retval;
1295
1296 retval = unshare_files(&displaced);
1297 if (retval)
1298 goto out_ret;
1299
1300 retval = -ENOMEM;
1301 bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1302 if (!bprm)
1303 goto out_files;
1304
1305 retval = prepare_bprm_creds(bprm);
1306 if (retval)
1307 goto out_free;
1308
1309 retval = check_unsafe_exec(bprm);
1310 if (retval < 0)
1311 goto out_free;
1312 clear_in_exec = retval;
1313 current->in_execve = 1;
1314
1315 file = open_exec(filename);
1316 retval = PTR_ERR(file);
1317 if (IS_ERR(file))
1318 goto out_unmark;
1319
1320 sched_exec();
1321
1322 bprm->file = file;
1323 bprm->filename = filename;
1324 bprm->interp = filename;
1325
1326 retval = bprm_mm_init(bprm);
1327 if (retval)
1328 goto out_file;
1329
1330 bprm->argc = count(argv, MAX_ARG_STRINGS);
1331 if ((retval = bprm->argc) < 0)
1332 goto out;
1333
1334 bprm->envc = count(envp, MAX_ARG_STRINGS);
1335 if ((retval = bprm->envc) < 0)
1336 goto out;
1337
1338 retval = prepare_binprm(bprm);
1339 if (retval < 0)
1340 goto out;
1341
1342 retval = copy_strings_kernel(1, &bprm->filename, bprm);
1343 if (retval < 0)
1344 goto out;
1345
1346 bprm->exec = bprm->p;
1347 retval = copy_strings(bprm->envc, envp, bprm);
1348 if (retval < 0)
1349 goto out;
1350
1351 retval = copy_strings(bprm->argc, argv, bprm);
1352 if (retval < 0)
1353 goto out;
1354
1355 current->flags &= ~PF_KTHREAD;
1356 retval = search_binary_handler(bprm,regs);
1357 if (retval < 0)
1358 goto out;
1359
1360 current->stack_start = current->mm->start_stack;
1361
1362 /* execve succeeded */
1363 current->fs->in_exec = 0;
1364 current->in_execve = 0;
1365 acct_update_integrals(current);
1366 free_bprm(bprm);
1367 if (displaced)
1368 put_files_struct(displaced);
1369 return retval;
1370
1371out:
1372 if (bprm->mm)
1373 mmput (bprm->mm);
1374
1375out_file:
1376 if (bprm->file) {
1377 allow_write_access(bprm->file);
1378 fput(bprm->file);
1379 }
1380
1381out_unmark:
1382 if (clear_in_exec)
1383 current->fs->in_exec = 0;
1384 current->in_execve = 0;
1385
1386out_free:
1387 free_bprm(bprm);
1388
1389out_files:
1390 if (displaced)
1391 reset_files_struct(displaced);
1392out_ret:
1393 return retval;
1394}
1395
1396void set_binfmt(struct linux_binfmt *new)
1397{
1398 struct mm_struct *mm = current->mm;
1399
1400 if (mm->binfmt)
1401 module_put(mm->binfmt->module);
1402
1403 mm->binfmt = new;
1404 if (new)
1405 __module_get(new->module);
1406}
1407
1408EXPORT_SYMBOL(set_binfmt);
1409
1410/* format_corename will inspect the pattern parameter, and output a
1411 * name into corename, which must have space for at least
1412 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
1413 */
1414static int format_corename(char *corename, long signr)
1415{
1416 const struct cred *cred = current_cred();
1417 const char *pat_ptr = core_pattern;
1418 int ispipe = (*pat_ptr == '|');
1419 char *out_ptr = corename;
1420 char *const out_end = corename + CORENAME_MAX_SIZE;
1421 int rc;
1422 int pid_in_pattern = 0;
1423
1424 /* Repeat as long as we have more pattern to process and more output
1425 space */
1426 while (*pat_ptr) {
1427 if (*pat_ptr != '%') {
1428 if (out_ptr == out_end)
1429 goto out;
1430 *out_ptr++ = *pat_ptr++;
1431 } else {
1432 switch (*++pat_ptr) {
1433 case 0:
1434 goto out;
1435 /* Double percent, output one percent */
1436 case '%':
1437 if (out_ptr == out_end)
1438 goto out;
1439 *out_ptr++ = '%';
1440 break;
1441 /* pid */
1442 case 'p':
1443 pid_in_pattern = 1;
1444 rc = snprintf(out_ptr, out_end - out_ptr,
1445 "%d", task_tgid_vnr(current));
1446 if (rc > out_end - out_ptr)
1447 goto out;
1448 out_ptr += rc;
1449 break;
1450 /* uid */
1451 case 'u':
1452 rc = snprintf(out_ptr, out_end - out_ptr,
1453 "%d", cred->uid);
1454 if (rc > out_end - out_ptr)
1455 goto out;
1456 out_ptr += rc;
1457 break;
1458 /* gid */
1459 case 'g':
1460 rc = snprintf(out_ptr, out_end - out_ptr,
1461 "%d", cred->gid);
1462 if (rc > out_end - out_ptr)
1463 goto out;
1464 out_ptr += rc;
1465 break;
1466 /* signal that caused the coredump */
1467 case 's':
1468 rc = snprintf(out_ptr, out_end - out_ptr,
1469 "%ld", signr);
1470 if (rc > out_end - out_ptr)
1471 goto out;
1472 out_ptr += rc;
1473 break;
1474 /* UNIX time of coredump */
1475 case 't': {
1476 struct timeval tv;
1477 do_gettimeofday(&tv);
1478 rc = snprintf(out_ptr, out_end - out_ptr,
1479 "%lu", tv.tv_sec);
1480 if (rc > out_end - out_ptr)
1481 goto out;
1482 out_ptr += rc;
1483 break;
1484 }
1485 /* hostname */
1486 case 'h':
1487 down_read(&uts_sem);
1488 rc = snprintf(out_ptr, out_end - out_ptr,
1489 "%s", utsname()->nodename);
1490 up_read(&uts_sem);
1491 if (rc > out_end - out_ptr)
1492 goto out;
1493 out_ptr += rc;
1494 break;
1495 /* executable */
1496 case 'e':
1497 rc = snprintf(out_ptr, out_end - out_ptr,
1498 "%s", current->comm);
1499 if (rc > out_end - out_ptr)
1500 goto out;
1501 out_ptr += rc;
1502 break;
1503 /* core limit size */
1504 case 'c':
1505 rc = snprintf(out_ptr, out_end - out_ptr,
1506 "%lu", current->signal->rlim[RLIMIT_CORE].rlim_cur);
1507 if (rc > out_end - out_ptr)
1508 goto out;
1509 out_ptr += rc;
1510 break;
1511 default:
1512 break;
1513 }
1514 ++pat_ptr;
1515 }
1516 }
1517 /* Backward compatibility with core_uses_pid:
1518 *
1519 * If core_pattern does not include a %p (as is the default)
1520 * and core_uses_pid is set, then .%pid will be appended to
1521 * the filename. Do not do this for piped commands. */
1522 if (!ispipe && !pid_in_pattern && core_uses_pid) {
1523 rc = snprintf(out_ptr, out_end - out_ptr,
1524 ".%d", task_tgid_vnr(current));
1525 if (rc > out_end - out_ptr)
1526 goto out;
1527 out_ptr += rc;
1528 }
1529out:
1530 *out_ptr = 0;
1531 return ispipe;
1532}
1533
1534static int zap_process(struct task_struct *start)
1535{
1536 struct task_struct *t;
1537 int nr = 0;
1538
1539 start->signal->flags = SIGNAL_GROUP_EXIT;
1540 start->signal->group_stop_count = 0;
1541
1542 t = start;
1543 do {
1544 if (t != current && t->mm) {
1545 sigaddset(&t->pending.signal, SIGKILL);
1546 signal_wake_up(t, 1);
1547 nr++;
1548 }
1549 } while_each_thread(start, t);
1550
1551 return nr;
1552}
1553
1554static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
1555 struct core_state *core_state, int exit_code)
1556{
1557 struct task_struct *g, *p;
1558 unsigned long flags;
1559 int nr = -EAGAIN;
1560
1561 spin_lock_irq(&tsk->sighand->siglock);
1562 if (!signal_group_exit(tsk->signal)) {
1563 mm->core_state = core_state;
1564 tsk->signal->group_exit_code = exit_code;
1565 nr = zap_process(tsk);
1566 }
1567 spin_unlock_irq(&tsk->sighand->siglock);
1568 if (unlikely(nr < 0))
1569 return nr;
1570
1571 if (atomic_read(&mm->mm_users) == nr + 1)
1572 goto done;
1573 /*
1574 * We should find and kill all tasks which use this mm, and we should
1575 * count them correctly into ->nr_threads. We don't take tasklist
1576 * lock, but this is safe wrt:
1577 *
1578 * fork:
1579 * None of sub-threads can fork after zap_process(leader). All
1580 * processes which were created before this point should be
1581 * visible to zap_threads() because copy_process() adds the new
1582 * process to the tail of init_task.tasks list, and lock/unlock
1583 * of ->siglock provides a memory barrier.
1584 *
1585 * do_exit:
1586 * The caller holds mm->mmap_sem. This means that the task which
1587 * uses this mm can't pass exit_mm(), so it can't exit or clear
1588 * its ->mm.
1589 *
1590 * de_thread:
1591 * It does list_replace_rcu(&leader->tasks, &current->tasks),
1592 * we must see either old or new leader, this does not matter.
1593 * However, it can change p->sighand, so lock_task_sighand(p)
1594 * must be used. Since p->mm != NULL and we hold ->mmap_sem
1595 * it can't fail.
1596 *
1597 * Note also that "g" can be the old leader with ->mm == NULL
1598 * and already unhashed and thus removed from ->thread_group.
1599 * This is OK, __unhash_process()->list_del_rcu() does not
1600 * clear the ->next pointer, we will find the new leader via
1601 * next_thread().
1602 */
1603 rcu_read_lock();
1604 for_each_process(g) {
1605 if (g == tsk->group_leader)
1606 continue;
1607 if (g->flags & PF_KTHREAD)
1608 continue;
1609 p = g;
1610 do {
1611 if (p->mm) {
1612 if (unlikely(p->mm == mm)) {
1613 lock_task_sighand(p, &flags);
1614 nr += zap_process(p);
1615 unlock_task_sighand(p, &flags);
1616 }
1617 break;
1618 }
1619 } while_each_thread(g, p);
1620 }
1621 rcu_read_unlock();
1622done:
1623 atomic_set(&core_state->nr_threads, nr);
1624 return nr;
1625}
1626
1627static int coredump_wait(int exit_code, struct core_state *core_state)
1628{
1629 struct task_struct *tsk = current;
1630 struct mm_struct *mm = tsk->mm;
1631 struct completion *vfork_done;
1632 int core_waiters;
1633
1634 init_completion(&core_state->startup);
1635 core_state->dumper.task = tsk;
1636 core_state->dumper.next = NULL;
1637 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
1638 up_write(&mm->mmap_sem);
1639
1640 if (unlikely(core_waiters < 0))
1641 goto fail;
1642
1643 /*
1644 * Make sure nobody is waiting for us to release the VM,
1645 * otherwise we can deadlock when we wait on each other
1646 */
1647 vfork_done = tsk->vfork_done;
1648 if (vfork_done) {
1649 tsk->vfork_done = NULL;
1650 complete(vfork_done);
1651 }
1652
1653 if (core_waiters)
1654 wait_for_completion(&core_state->startup);
1655fail:
1656 return core_waiters;
1657}
1658
1659static void coredump_finish(struct mm_struct *mm)
1660{
1661 struct core_thread *curr, *next;
1662 struct task_struct *task;
1663
1664 next = mm->core_state->dumper.next;
1665 while ((curr = next) != NULL) {
1666 next = curr->next;
1667 task = curr->task;
1668 /*
1669 * see exit_mm(), curr->task must not see
1670 * ->task == NULL before we read ->next.
1671 */
1672 smp_mb();
1673 curr->task = NULL;
1674 wake_up_process(task);
1675 }
1676
1677 mm->core_state = NULL;
1678}
1679
1680/*
1681 * set_dumpable converts traditional three-value dumpable to two flags and
1682 * stores them into mm->flags. It modifies lower two bits of mm->flags, but
1683 * these bits are not changed atomically. So get_dumpable can observe the
1684 * intermediate state. To avoid doing unexpected behavior, get get_dumpable
1685 * return either old dumpable or new one by paying attention to the order of
1686 * modifying the bits.
1687 *
1688 * dumpable | mm->flags (binary)
1689 * old new | initial interim final
1690 * ---------+-----------------------
1691 * 0 1 | 00 01 01
1692 * 0 2 | 00 10(*) 11
1693 * 1 0 | 01 00 00
1694 * 1 2 | 01 11 11
1695 * 2 0 | 11 10(*) 00
1696 * 2 1 | 11 11 01
1697 *
1698 * (*) get_dumpable regards interim value of 10 as 11.
1699 */
1700void set_dumpable(struct mm_struct *mm, int value)
1701{
1702 switch (value) {
1703 case 0:
1704 clear_bit(MMF_DUMPABLE, &mm->flags);
1705 smp_wmb();
1706 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1707 break;
1708 case 1:
1709 set_bit(MMF_DUMPABLE, &mm->flags);
1710 smp_wmb();
1711 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1712 break;
1713 case 2:
1714 set_bit(MMF_DUMP_SECURELY, &mm->flags);
1715 smp_wmb();
1716 set_bit(MMF_DUMPABLE, &mm->flags);
1717 break;
1718 }
1719}
1720
1721int get_dumpable(struct mm_struct *mm)
1722{
1723 int ret;
1724
1725 ret = mm->flags & 0x3;
1726 return (ret >= 2) ? 2 : ret;
1727}
1728
1729static void wait_for_dump_helpers(struct file *file)
1730{
1731 struct pipe_inode_info *pipe;
1732
1733 pipe = file->f_path.dentry->d_inode->i_pipe;
1734
1735 pipe_lock(pipe);
1736 pipe->readers++;
1737 pipe->writers--;
1738
1739 while ((pipe->readers > 1) && (!signal_pending(current))) {
1740 wake_up_interruptible_sync(&pipe->wait);
1741 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
1742 pipe_wait(pipe);
1743 }
1744
1745 pipe->readers--;
1746 pipe->writers++;
1747 pipe_unlock(pipe);
1748
1749}
1750
1751
1752void do_coredump(long signr, int exit_code, struct pt_regs *regs)
1753{
1754 struct core_state core_state;
1755 char corename[CORENAME_MAX_SIZE + 1];
1756 struct mm_struct *mm = current->mm;
1757 struct linux_binfmt * binfmt;
1758 struct inode * inode;
1759 struct file * file;
1760 const struct cred *old_cred;
1761 struct cred *cred;
1762 int retval = 0;
1763 int flag = 0;
1764 int ispipe = 0;
1765 unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
1766 char **helper_argv = NULL;
1767 int helper_argc = 0;
1768 int dump_count = 0;
1769 static atomic_t core_dump_count = ATOMIC_INIT(0);
1770
1771 audit_core_dumps(signr);
1772
1773 binfmt = mm->binfmt;
1774 if (!binfmt || !binfmt->core_dump)
1775 goto fail;
1776
1777 cred = prepare_creds();
1778 if (!cred) {
1779 retval = -ENOMEM;
1780 goto fail;
1781 }
1782
1783 down_write(&mm->mmap_sem);
1784 /*
1785 * If another thread got here first, or we are not dumpable, bail out.
1786 */
1787 if (mm->core_state || !get_dumpable(mm)) {
1788 up_write(&mm->mmap_sem);
1789 put_cred(cred);
1790 goto fail;
1791 }
1792
1793 /*
1794 * We cannot trust fsuid as being the "true" uid of the
1795 * process nor do we know its entire history. We only know it
1796 * was tainted so we dump it as root in mode 2.
1797 */
1798 if (get_dumpable(mm) == 2) { /* Setuid core dump mode */
1799 flag = O_EXCL; /* Stop rewrite attacks */
1800 cred->fsuid = 0; /* Dump root private */
1801 }
1802
1803 retval = coredump_wait(exit_code, &core_state);
1804 if (retval < 0) {
1805 put_cred(cred);
1806 goto fail;
1807 }
1808
1809 old_cred = override_creds(cred);
1810
1811 /*
1812 * Clear any false indication of pending signals that might
1813 * be seen by the filesystem code called to write the core file.
1814 */
1815 clear_thread_flag(TIF_SIGPENDING);
1816
1817 /*
1818 * lock_kernel() because format_corename() is controlled by sysctl, which
1819 * uses lock_kernel()
1820 */
1821 lock_kernel();
1822 ispipe = format_corename(corename, signr);
1823 unlock_kernel();
1824
1825 if ((!ispipe) && (core_limit < binfmt->min_coredump))
1826 goto fail_unlock;
1827
1828 if (ispipe) {
1829 if (core_limit == 0) {
1830 /*
1831 * Normally core limits are irrelevant to pipes, since
1832 * we're not writing to the file system, but we use
1833 * core_limit of 0 here as a speacial value. Any
1834 * non-zero limit gets set to RLIM_INFINITY below, but
1835 * a limit of 0 skips the dump. This is a consistent
1836 * way to catch recursive crashes. We can still crash
1837 * if the core_pattern binary sets RLIM_CORE = !0
1838 * but it runs as root, and can do lots of stupid things
1839 * Note that we use task_tgid_vnr here to grab the pid
1840 * of the process group leader. That way we get the
1841 * right pid if a thread in a multi-threaded
1842 * core_pattern process dies.
1843 */
1844 printk(KERN_WARNING
1845 "Process %d(%s) has RLIMIT_CORE set to 0\n",
1846 task_tgid_vnr(current), current->comm);
1847 printk(KERN_WARNING "Aborting core\n");
1848 goto fail_unlock;
1849 }
1850
1851 dump_count = atomic_inc_return(&core_dump_count);
1852 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
1853 printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
1854 task_tgid_vnr(current), current->comm);
1855 printk(KERN_WARNING "Skipping core dump\n");
1856 goto fail_dropcount;
1857 }
1858
1859 helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc);
1860 if (!helper_argv) {
1861 printk(KERN_WARNING "%s failed to allocate memory\n",
1862 __func__);
1863 goto fail_dropcount;
1864 }
1865
1866 core_limit = RLIM_INFINITY;
1867
1868 /* SIGPIPE can happen, but it's just never processed */
1869 if (call_usermodehelper_pipe(helper_argv[0], helper_argv, NULL,
1870 &file)) {
1871 printk(KERN_INFO "Core dump to %s pipe failed\n",
1872 corename);
1873 goto fail_dropcount;
1874 }
1875 } else
1876 file = filp_open(corename,
1877 O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
1878 0600);
1879 if (IS_ERR(file))
1880 goto fail_dropcount;
1881 inode = file->f_path.dentry->d_inode;
1882 if (inode->i_nlink > 1)
1883 goto close_fail; /* multiple links - don't dump */
1884 if (!ispipe && d_unhashed(file->f_path.dentry))
1885 goto close_fail;
1886
1887 /* AK: actually i see no reason to not allow this for named pipes etc.,
1888 but keep the previous behaviour for now. */
1889 if (!ispipe && !S_ISREG(inode->i_mode))
1890 goto close_fail;
1891 /*
1892 * Dont allow local users get cute and trick others to coredump
1893 * into their pre-created files:
1894 */
1895 if (inode->i_uid != current_fsuid())
1896 goto close_fail;
1897 if (!file->f_op)
1898 goto close_fail;
1899 if (!file->f_op->write)
1900 goto close_fail;
1901 if (!ispipe && do_truncate(file->f_path.dentry, 0, 0, file) != 0)
1902 goto close_fail;
1903
1904 retval = binfmt->core_dump(signr, regs, file, core_limit);
1905
1906 if (retval)
1907 current->signal->group_exit_code |= 0x80;
1908close_fail:
1909 if (ispipe && core_pipe_limit)
1910 wait_for_dump_helpers(file);
1911 filp_close(file, NULL);
1912fail_dropcount:
1913 if (dump_count)
1914 atomic_dec(&core_dump_count);
1915fail_unlock:
1916 if (helper_argv)
1917 argv_free(helper_argv);
1918
1919 revert_creds(old_cred);
1920 put_cred(cred);
1921 coredump_finish(mm);
1922fail:
1923 return;
1924}