fs/exec.c: fix initial stack reservation
[linux-2.6.git] / fs / exec.c
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/syscalls.h>
50 #include <linux/tsacct_kern.h>
51 #include <linux/cn_proc.h>
52 #include <linux/audit.h>
53 #include <linux/tracehook.h>
54 #include <linux/kmod.h>
55 #include <linux/fsnotify.h>
56 #include <linux/fs_struct.h>
57 #include <linux/pipe_fs_i.h>
58
59 #include <asm/uaccess.h>
60 #include <asm/mmu_context.h>
61 #include <asm/tlb.h>
62 #include "internal.h"
63
64 int core_uses_pid;
65 char core_pattern[CORENAME_MAX_SIZE] = "core";
66 unsigned int core_pipe_limit;
67 int suid_dumpable = 0;
68
69 /* The maximal length of core_pattern is also specified in sysctl.c */
70
71 static LIST_HEAD(formats);
72 static DEFINE_RWLOCK(binfmt_lock);
73
74 int __register_binfmt(struct linux_binfmt * fmt, int insert)
75 {
76         if (!fmt)
77                 return -EINVAL;
78         write_lock(&binfmt_lock);
79         insert ? list_add(&fmt->lh, &formats) :
80                  list_add_tail(&fmt->lh, &formats);
81         write_unlock(&binfmt_lock);
82         return 0;       
83 }
84
85 EXPORT_SYMBOL(__register_binfmt);
86
87 void unregister_binfmt(struct linux_binfmt * fmt)
88 {
89         write_lock(&binfmt_lock);
90         list_del(&fmt->lh);
91         write_unlock(&binfmt_lock);
92 }
93
94 EXPORT_SYMBOL(unregister_binfmt);
95
96 static inline void put_binfmt(struct linux_binfmt * fmt)
97 {
98         module_put(fmt->module);
99 }
100
101 /*
102  * Note that a shared library must be both readable and executable due to
103  * security reasons.
104  *
105  * Also note that we take the address to load from from the file itself.
106  */
107 SYSCALL_DEFINE1(uselib, const char __user *, library)
108 {
109         struct file *file;
110         char *tmp = getname(library);
111         int error = PTR_ERR(tmp);
112
113         if (IS_ERR(tmp))
114                 goto out;
115
116         file = do_filp_open(AT_FDCWD, tmp,
117                                 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0,
118                                 MAY_READ | MAY_EXEC | MAY_OPEN);
119         putname(tmp);
120         error = PTR_ERR(file);
121         if (IS_ERR(file))
122                 goto out;
123
124         error = -EINVAL;
125         if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
126                 goto exit;
127
128         error = -EACCES;
129         if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
130                 goto exit;
131
132         fsnotify_open(file->f_path.dentry);
133
134         error = -ENOEXEC;
135         if(file->f_op) {
136                 struct linux_binfmt * fmt;
137
138                 read_lock(&binfmt_lock);
139                 list_for_each_entry(fmt, &formats, lh) {
140                         if (!fmt->load_shlib)
141                                 continue;
142                         if (!try_module_get(fmt->module))
143                                 continue;
144                         read_unlock(&binfmt_lock);
145                         error = fmt->load_shlib(file);
146                         read_lock(&binfmt_lock);
147                         put_binfmt(fmt);
148                         if (error != -ENOEXEC)
149                                 break;
150                 }
151                 read_unlock(&binfmt_lock);
152         }
153 exit:
154         fput(file);
155 out:
156         return error;
157 }
158
159 #ifdef CONFIG_MMU
160
161 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
162                 int write)
163 {
164         struct page *page;
165         int ret;
166
167 #ifdef CONFIG_STACK_GROWSUP
168         if (write) {
169                 ret = expand_stack_downwards(bprm->vma, pos);
170                 if (ret < 0)
171                         return NULL;
172         }
173 #endif
174         ret = get_user_pages(current, bprm->mm, pos,
175                         1, write, 1, &page, NULL);
176         if (ret <= 0)
177                 return NULL;
178
179         if (write) {
180                 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
181                 struct rlimit *rlim;
182
183                 /*
184                  * We've historically supported up to 32 pages (ARG_MAX)
185                  * of argument strings even with small stacks
186                  */
187                 if (size <= ARG_MAX)
188                         return page;
189
190                 /*
191                  * Limit to 1/4-th the stack size for the argv+env strings.
192                  * This ensures that:
193                  *  - the remaining binfmt code will not run out of stack space,
194                  *  - the program will have a reasonable amount of stack left
195                  *    to work from.
196                  */
197                 rlim = current->signal->rlim;
198                 if (size > rlim[RLIMIT_STACK].rlim_cur / 4) {
199                         put_page(page);
200                         return NULL;
201                 }
202         }
203
204         return page;
205 }
206
207 static void put_arg_page(struct page *page)
208 {
209         put_page(page);
210 }
211
212 static void free_arg_page(struct linux_binprm *bprm, int i)
213 {
214 }
215
216 static void free_arg_pages(struct linux_binprm *bprm)
217 {
218 }
219
220 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
221                 struct page *page)
222 {
223         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
224 }
225
226 static int __bprm_mm_init(struct linux_binprm *bprm)
227 {
228         int err;
229         struct vm_area_struct *vma = NULL;
230         struct mm_struct *mm = bprm->mm;
231
232         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
233         if (!vma)
234                 return -ENOMEM;
235
236         down_write(&mm->mmap_sem);
237         vma->vm_mm = mm;
238
239         /*
240          * Place the stack at the largest stack address the architecture
241          * supports. Later, we'll move this to an appropriate place. We don't
242          * use STACK_TOP because that can depend on attributes which aren't
243          * configured yet.
244          */
245         vma->vm_end = STACK_TOP_MAX;
246         vma->vm_start = vma->vm_end - PAGE_SIZE;
247         vma->vm_flags = VM_STACK_FLAGS;
248         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
249         err = insert_vm_struct(mm, vma);
250         if (err)
251                 goto err;
252
253         mm->stack_vm = mm->total_vm = 1;
254         up_write(&mm->mmap_sem);
255         bprm->p = vma->vm_end - sizeof(void *);
256         return 0;
257 err:
258         up_write(&mm->mmap_sem);
259         bprm->vma = NULL;
260         kmem_cache_free(vm_area_cachep, vma);
261         return err;
262 }
263
264 static bool valid_arg_len(struct linux_binprm *bprm, long len)
265 {
266         return len <= MAX_ARG_STRLEN;
267 }
268
269 #else
270
271 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
272                 int write)
273 {
274         struct page *page;
275
276         page = bprm->page[pos / PAGE_SIZE];
277         if (!page && write) {
278                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
279                 if (!page)
280                         return NULL;
281                 bprm->page[pos / PAGE_SIZE] = page;
282         }
283
284         return page;
285 }
286
287 static void put_arg_page(struct page *page)
288 {
289 }
290
291 static void free_arg_page(struct linux_binprm *bprm, int i)
292 {
293         if (bprm->page[i]) {
294                 __free_page(bprm->page[i]);
295                 bprm->page[i] = NULL;
296         }
297 }
298
299 static void free_arg_pages(struct linux_binprm *bprm)
300 {
301         int i;
302
303         for (i = 0; i < MAX_ARG_PAGES; i++)
304                 free_arg_page(bprm, i);
305 }
306
307 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
308                 struct page *page)
309 {
310 }
311
312 static int __bprm_mm_init(struct linux_binprm *bprm)
313 {
314         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
315         return 0;
316 }
317
318 static bool valid_arg_len(struct linux_binprm *bprm, long len)
319 {
320         return len <= bprm->p;
321 }
322
323 #endif /* CONFIG_MMU */
324
325 /*
326  * Create a new mm_struct and populate it with a temporary stack
327  * vm_area_struct.  We don't have enough context at this point to set the stack
328  * flags, permissions, and offset, so we use temporary values.  We'll update
329  * them later in setup_arg_pages().
330  */
331 int bprm_mm_init(struct linux_binprm *bprm)
332 {
333         int err;
334         struct mm_struct *mm = NULL;
335
336         bprm->mm = mm = mm_alloc();
337         err = -ENOMEM;
338         if (!mm)
339                 goto err;
340
341         err = init_new_context(current, mm);
342         if (err)
343                 goto err;
344
345         err = __bprm_mm_init(bprm);
346         if (err)
347                 goto err;
348
349         return 0;
350
351 err:
352         if (mm) {
353                 bprm->mm = NULL;
354                 mmdrop(mm);
355         }
356
357         return err;
358 }
359
360 /*
361  * count() counts the number of strings in array ARGV.
362  */
363 static int count(char __user * __user * argv, int max)
364 {
365         int i = 0;
366
367         if (argv != NULL) {
368                 for (;;) {
369                         char __user * p;
370
371                         if (get_user(p, argv))
372                                 return -EFAULT;
373                         if (!p)
374                                 break;
375                         argv++;
376                         if (i++ >= max)
377                                 return -E2BIG;
378                         cond_resched();
379                 }
380         }
381         return i;
382 }
383
384 /*
385  * 'copy_strings()' copies argument/environment strings from the old
386  * processes's memory to the new process's stack.  The call to get_user_pages()
387  * ensures the destination page is created and not swapped out.
388  */
389 static int copy_strings(int argc, char __user * __user * argv,
390                         struct linux_binprm *bprm)
391 {
392         struct page *kmapped_page = NULL;
393         char *kaddr = NULL;
394         unsigned long kpos = 0;
395         int ret;
396
397         while (argc-- > 0) {
398                 char __user *str;
399                 int len;
400                 unsigned long pos;
401
402                 if (get_user(str, argv+argc) ||
403                                 !(len = strnlen_user(str, MAX_ARG_STRLEN))) {
404                         ret = -EFAULT;
405                         goto out;
406                 }
407
408                 if (!valid_arg_len(bprm, len)) {
409                         ret = -E2BIG;
410                         goto out;
411                 }
412
413                 /* We're going to work our way backwords. */
414                 pos = bprm->p;
415                 str += len;
416                 bprm->p -= len;
417
418                 while (len > 0) {
419                         int offset, bytes_to_copy;
420
421                         offset = pos % PAGE_SIZE;
422                         if (offset == 0)
423                                 offset = PAGE_SIZE;
424
425                         bytes_to_copy = offset;
426                         if (bytes_to_copy > len)
427                                 bytes_to_copy = len;
428
429                         offset -= bytes_to_copy;
430                         pos -= bytes_to_copy;
431                         str -= bytes_to_copy;
432                         len -= bytes_to_copy;
433
434                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
435                                 struct page *page;
436
437                                 page = get_arg_page(bprm, pos, 1);
438                                 if (!page) {
439                                         ret = -E2BIG;
440                                         goto out;
441                                 }
442
443                                 if (kmapped_page) {
444                                         flush_kernel_dcache_page(kmapped_page);
445                                         kunmap(kmapped_page);
446                                         put_arg_page(kmapped_page);
447                                 }
448                                 kmapped_page = page;
449                                 kaddr = kmap(kmapped_page);
450                                 kpos = pos & PAGE_MASK;
451                                 flush_arg_page(bprm, kpos, kmapped_page);
452                         }
453                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
454                                 ret = -EFAULT;
455                                 goto out;
456                         }
457                 }
458         }
459         ret = 0;
460 out:
461         if (kmapped_page) {
462                 flush_kernel_dcache_page(kmapped_page);
463                 kunmap(kmapped_page);
464                 put_arg_page(kmapped_page);
465         }
466         return ret;
467 }
468
469 /*
470  * Like copy_strings, but get argv and its values from kernel memory.
471  */
472 int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm)
473 {
474         int r;
475         mm_segment_t oldfs = get_fs();
476         set_fs(KERNEL_DS);
477         r = copy_strings(argc, (char __user * __user *)argv, bprm);
478         set_fs(oldfs);
479         return r;
480 }
481 EXPORT_SYMBOL(copy_strings_kernel);
482
483 #ifdef CONFIG_MMU
484
485 /*
486  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
487  * the binfmt code determines where the new stack should reside, we shift it to
488  * its final location.  The process proceeds as follows:
489  *
490  * 1) Use shift to calculate the new vma endpoints.
491  * 2) Extend vma to cover both the old and new ranges.  This ensures the
492  *    arguments passed to subsequent functions are consistent.
493  * 3) Move vma's page tables to the new range.
494  * 4) Free up any cleared pgd range.
495  * 5) Shrink the vma to cover only the new range.
496  */
497 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
498 {
499         struct mm_struct *mm = vma->vm_mm;
500         unsigned long old_start = vma->vm_start;
501         unsigned long old_end = vma->vm_end;
502         unsigned long length = old_end - old_start;
503         unsigned long new_start = old_start - shift;
504         unsigned long new_end = old_end - shift;
505         struct mmu_gather *tlb;
506
507         BUG_ON(new_start > new_end);
508
509         /*
510          * ensure there are no vmas between where we want to go
511          * and where we are
512          */
513         if (vma != find_vma(mm, new_start))
514                 return -EFAULT;
515
516         /*
517          * cover the whole range: [new_start, old_end)
518          */
519         vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL);
520
521         /*
522          * move the page tables downwards, on failure we rely on
523          * process cleanup to remove whatever mess we made.
524          */
525         if (length != move_page_tables(vma, old_start,
526                                        vma, new_start, length))
527                 return -ENOMEM;
528
529         lru_add_drain();
530         tlb = tlb_gather_mmu(mm, 0);
531         if (new_end > old_start) {
532                 /*
533                  * when the old and new regions overlap clear from new_end.
534                  */
535                 free_pgd_range(tlb, new_end, old_end, new_end,
536                         vma->vm_next ? vma->vm_next->vm_start : 0);
537         } else {
538                 /*
539                  * otherwise, clean from old_start; this is done to not touch
540                  * the address space in [new_end, old_start) some architectures
541                  * have constraints on va-space that make this illegal (IA64) -
542                  * for the others its just a little faster.
543                  */
544                 free_pgd_range(tlb, old_start, old_end, new_end,
545                         vma->vm_next ? vma->vm_next->vm_start : 0);
546         }
547         tlb_finish_mmu(tlb, new_end, old_end);
548
549         /*
550          * shrink the vma to just the new range.
551          */
552         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
553
554         return 0;
555 }
556
557 #define EXTRA_STACK_VM_PAGES    20      /* random */
558
559 /*
560  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
561  * the stack is optionally relocated, and some extra space is added.
562  */
563 int setup_arg_pages(struct linux_binprm *bprm,
564                     unsigned long stack_top,
565                     int executable_stack)
566 {
567         unsigned long ret;
568         unsigned long stack_shift;
569         struct mm_struct *mm = current->mm;
570         struct vm_area_struct *vma = bprm->vma;
571         struct vm_area_struct *prev = NULL;
572         unsigned long vm_flags;
573         unsigned long stack_base;
574         unsigned long stack_size;
575         unsigned long stack_expand;
576         unsigned long rlim_stack;
577
578 #ifdef CONFIG_STACK_GROWSUP
579         /* Limit stack size to 1GB */
580         stack_base = current->signal->rlim[RLIMIT_STACK].rlim_max;
581         if (stack_base > (1 << 30))
582                 stack_base = 1 << 30;
583
584         /* Make sure we didn't let the argument array grow too large. */
585         if (vma->vm_end - vma->vm_start > stack_base)
586                 return -ENOMEM;
587
588         stack_base = PAGE_ALIGN(stack_top - stack_base);
589
590         stack_shift = vma->vm_start - stack_base;
591         mm->arg_start = bprm->p - stack_shift;
592         bprm->p = vma->vm_end - stack_shift;
593 #else
594         stack_top = arch_align_stack(stack_top);
595         stack_top = PAGE_ALIGN(stack_top);
596         stack_shift = vma->vm_end - stack_top;
597
598         bprm->p -= stack_shift;
599         mm->arg_start = bprm->p;
600 #endif
601
602         if (bprm->loader)
603                 bprm->loader -= stack_shift;
604         bprm->exec -= stack_shift;
605
606         down_write(&mm->mmap_sem);
607         vm_flags = VM_STACK_FLAGS;
608
609         /*
610          * Adjust stack execute permissions; explicitly enable for
611          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
612          * (arch default) otherwise.
613          */
614         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
615                 vm_flags |= VM_EXEC;
616         else if (executable_stack == EXSTACK_DISABLE_X)
617                 vm_flags &= ~VM_EXEC;
618         vm_flags |= mm->def_flags;
619
620         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
621                         vm_flags);
622         if (ret)
623                 goto out_unlock;
624         BUG_ON(prev != vma);
625
626         /* Move stack pages down in memory. */
627         if (stack_shift) {
628                 ret = shift_arg_pages(vma, stack_shift);
629                 if (ret)
630                         goto out_unlock;
631         }
632
633         stack_expand = EXTRA_STACK_VM_PAGES * PAGE_SIZE;
634         stack_size = vma->vm_end - vma->vm_start;
635         /*
636          * Align this down to a page boundary as expand_stack
637          * will align it up.
638          */
639         rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
640 #ifdef CONFIG_STACK_GROWSUP
641         if (stack_size + stack_expand > rlim_stack)
642                 stack_base = vma->vm_start + rlim_stack;
643         else
644                 stack_base = vma->vm_end + stack_expand;
645 #else
646         if (stack_size + stack_expand > rlim_stack)
647                 stack_base = vma->vm_end - rlim_stack;
648         else
649                 stack_base = vma->vm_start - stack_expand;
650 #endif
651         ret = expand_stack(vma, stack_base);
652         if (ret)
653                 ret = -EFAULT;
654
655 out_unlock:
656         up_write(&mm->mmap_sem);
657         return ret;
658 }
659 EXPORT_SYMBOL(setup_arg_pages);
660
661 #endif /* CONFIG_MMU */
662
663 struct file *open_exec(const char *name)
664 {
665         struct file *file;
666         int err;
667
668         file = do_filp_open(AT_FDCWD, name,
669                                 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0,
670                                 MAY_EXEC | MAY_OPEN);
671         if (IS_ERR(file))
672                 goto out;
673
674         err = -EACCES;
675         if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
676                 goto exit;
677
678         if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
679                 goto exit;
680
681         fsnotify_open(file->f_path.dentry);
682
683         err = deny_write_access(file);
684         if (err)
685                 goto exit;
686
687 out:
688         return file;
689
690 exit:
691         fput(file);
692         return ERR_PTR(err);
693 }
694 EXPORT_SYMBOL(open_exec);
695
696 int kernel_read(struct file *file, loff_t offset,
697                 char *addr, unsigned long count)
698 {
699         mm_segment_t old_fs;
700         loff_t pos = offset;
701         int result;
702
703         old_fs = get_fs();
704         set_fs(get_ds());
705         /* The cast to a user pointer is valid due to the set_fs() */
706         result = vfs_read(file, (void __user *)addr, count, &pos);
707         set_fs(old_fs);
708         return result;
709 }
710
711 EXPORT_SYMBOL(kernel_read);
712
713 static int exec_mmap(struct mm_struct *mm)
714 {
715         struct task_struct *tsk;
716         struct mm_struct * old_mm, *active_mm;
717
718         /* Notify parent that we're no longer interested in the old VM */
719         tsk = current;
720         old_mm = current->mm;
721         mm_release(tsk, old_mm);
722
723         if (old_mm) {
724                 /*
725                  * Make sure that if there is a core dump in progress
726                  * for the old mm, we get out and die instead of going
727                  * through with the exec.  We must hold mmap_sem around
728                  * checking core_state and changing tsk->mm.
729                  */
730                 down_read(&old_mm->mmap_sem);
731                 if (unlikely(old_mm->core_state)) {
732                         up_read(&old_mm->mmap_sem);
733                         return -EINTR;
734                 }
735         }
736         task_lock(tsk);
737         active_mm = tsk->active_mm;
738         tsk->mm = mm;
739         tsk->active_mm = mm;
740         activate_mm(active_mm, mm);
741         task_unlock(tsk);
742         arch_pick_mmap_layout(mm);
743         if (old_mm) {
744                 up_read(&old_mm->mmap_sem);
745                 BUG_ON(active_mm != old_mm);
746                 mm_update_next_owner(old_mm);
747                 mmput(old_mm);
748                 return 0;
749         }
750         mmdrop(active_mm);
751         return 0;
752 }
753
754 /*
755  * This function makes sure the current process has its own signal table,
756  * so that flush_signal_handlers can later reset the handlers without
757  * disturbing other processes.  (Other processes might share the signal
758  * table via the CLONE_SIGHAND option to clone().)
759  */
760 static int de_thread(struct task_struct *tsk)
761 {
762         struct signal_struct *sig = tsk->signal;
763         struct sighand_struct *oldsighand = tsk->sighand;
764         spinlock_t *lock = &oldsighand->siglock;
765         int count;
766
767         if (thread_group_empty(tsk))
768                 goto no_thread_group;
769
770         /*
771          * Kill all other threads in the thread group.
772          */
773         spin_lock_irq(lock);
774         if (signal_group_exit(sig)) {
775                 /*
776                  * Another group action in progress, just
777                  * return so that the signal is processed.
778                  */
779                 spin_unlock_irq(lock);
780                 return -EAGAIN;
781         }
782         sig->group_exit_task = tsk;
783         zap_other_threads(tsk);
784
785         /* Account for the thread group leader hanging around: */
786         count = thread_group_leader(tsk) ? 1 : 2;
787         sig->notify_count = count;
788         while (atomic_read(&sig->count) > count) {
789                 __set_current_state(TASK_UNINTERRUPTIBLE);
790                 spin_unlock_irq(lock);
791                 schedule();
792                 spin_lock_irq(lock);
793         }
794         spin_unlock_irq(lock);
795
796         /*
797          * At this point all other threads have exited, all we have to
798          * do is to wait for the thread group leader to become inactive,
799          * and to assume its PID:
800          */
801         if (!thread_group_leader(tsk)) {
802                 struct task_struct *leader = tsk->group_leader;
803
804                 sig->notify_count = -1; /* for exit_notify() */
805                 for (;;) {
806                         write_lock_irq(&tasklist_lock);
807                         if (likely(leader->exit_state))
808                                 break;
809                         __set_current_state(TASK_UNINTERRUPTIBLE);
810                         write_unlock_irq(&tasklist_lock);
811                         schedule();
812                 }
813
814                 /*
815                  * The only record we have of the real-time age of a
816                  * process, regardless of execs it's done, is start_time.
817                  * All the past CPU time is accumulated in signal_struct
818                  * from sister threads now dead.  But in this non-leader
819                  * exec, nothing survives from the original leader thread,
820                  * whose birth marks the true age of this process now.
821                  * When we take on its identity by switching to its PID, we
822                  * also take its birthdate (always earlier than our own).
823                  */
824                 tsk->start_time = leader->start_time;
825
826                 BUG_ON(!same_thread_group(leader, tsk));
827                 BUG_ON(has_group_leader_pid(tsk));
828                 /*
829                  * An exec() starts a new thread group with the
830                  * TGID of the previous thread group. Rehash the
831                  * two threads with a switched PID, and release
832                  * the former thread group leader:
833                  */
834
835                 /* Become a process group leader with the old leader's pid.
836                  * The old leader becomes a thread of the this thread group.
837                  * Note: The old leader also uses this pid until release_task
838                  *       is called.  Odd but simple and correct.
839                  */
840                 detach_pid(tsk, PIDTYPE_PID);
841                 tsk->pid = leader->pid;
842                 attach_pid(tsk, PIDTYPE_PID,  task_pid(leader));
843                 transfer_pid(leader, tsk, PIDTYPE_PGID);
844                 transfer_pid(leader, tsk, PIDTYPE_SID);
845
846                 list_replace_rcu(&leader->tasks, &tsk->tasks);
847                 list_replace_init(&leader->sibling, &tsk->sibling);
848
849                 tsk->group_leader = tsk;
850                 leader->group_leader = tsk;
851
852                 tsk->exit_signal = SIGCHLD;
853
854                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
855                 leader->exit_state = EXIT_DEAD;
856                 write_unlock_irq(&tasklist_lock);
857
858                 release_task(leader);
859         }
860
861         sig->group_exit_task = NULL;
862         sig->notify_count = 0;
863
864 no_thread_group:
865         if (current->mm)
866                 setmax_mm_hiwater_rss(&sig->maxrss, current->mm);
867
868         exit_itimers(sig);
869         flush_itimer_signals();
870
871         if (atomic_read(&oldsighand->count) != 1) {
872                 struct sighand_struct *newsighand;
873                 /*
874                  * This ->sighand is shared with the CLONE_SIGHAND
875                  * but not CLONE_THREAD task, switch to the new one.
876                  */
877                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
878                 if (!newsighand)
879                         return -ENOMEM;
880
881                 atomic_set(&newsighand->count, 1);
882                 memcpy(newsighand->action, oldsighand->action,
883                        sizeof(newsighand->action));
884
885                 write_lock_irq(&tasklist_lock);
886                 spin_lock(&oldsighand->siglock);
887                 rcu_assign_pointer(tsk->sighand, newsighand);
888                 spin_unlock(&oldsighand->siglock);
889                 write_unlock_irq(&tasklist_lock);
890
891                 __cleanup_sighand(oldsighand);
892         }
893
894         BUG_ON(!thread_group_leader(tsk));
895         return 0;
896 }
897
898 /*
899  * These functions flushes out all traces of the currently running executable
900  * so that a new one can be started
901  */
902 static void flush_old_files(struct files_struct * files)
903 {
904         long j = -1;
905         struct fdtable *fdt;
906
907         spin_lock(&files->file_lock);
908         for (;;) {
909                 unsigned long set, i;
910
911                 j++;
912                 i = j * __NFDBITS;
913                 fdt = files_fdtable(files);
914                 if (i >= fdt->max_fds)
915                         break;
916                 set = fdt->close_on_exec->fds_bits[j];
917                 if (!set)
918                         continue;
919                 fdt->close_on_exec->fds_bits[j] = 0;
920                 spin_unlock(&files->file_lock);
921                 for ( ; set ; i++,set >>= 1) {
922                         if (set & 1) {
923                                 sys_close(i);
924                         }
925                 }
926                 spin_lock(&files->file_lock);
927
928         }
929         spin_unlock(&files->file_lock);
930 }
931
932 char *get_task_comm(char *buf, struct task_struct *tsk)
933 {
934         /* buf must be at least sizeof(tsk->comm) in size */
935         task_lock(tsk);
936         strncpy(buf, tsk->comm, sizeof(tsk->comm));
937         task_unlock(tsk);
938         return buf;
939 }
940
941 void set_task_comm(struct task_struct *tsk, char *buf)
942 {
943         task_lock(tsk);
944
945         /*
946          * Threads may access current->comm without holding
947          * the task lock, so write the string carefully.
948          * Readers without a lock may see incomplete new
949          * names but are safe from non-terminating string reads.
950          */
951         memset(tsk->comm, 0, TASK_COMM_LEN);
952         wmb();
953         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
954         task_unlock(tsk);
955         perf_event_comm(tsk);
956 }
957
958 int flush_old_exec(struct linux_binprm * bprm)
959 {
960         int retval;
961
962         /*
963          * Make sure we have a private signal table and that
964          * we are unassociated from the previous thread group.
965          */
966         retval = de_thread(current);
967         if (retval)
968                 goto out;
969
970         set_mm_exe_file(bprm->mm, bprm->file);
971
972         /*
973          * Release all of the old mmap stuff
974          */
975         retval = exec_mmap(bprm->mm);
976         if (retval)
977                 goto out;
978
979         bprm->mm = NULL;                /* We're using it now */
980
981         current->flags &= ~PF_RANDOMIZE;
982         flush_thread();
983         current->personality &= ~bprm->per_clear;
984
985         return 0;
986
987 out:
988         return retval;
989 }
990 EXPORT_SYMBOL(flush_old_exec);
991
992 void setup_new_exec(struct linux_binprm * bprm)
993 {
994         int i, ch;
995         char * name;
996         char tcomm[sizeof(current->comm)];
997
998         arch_pick_mmap_layout(current->mm);
999
1000         /* This is the point of no return */
1001         current->sas_ss_sp = current->sas_ss_size = 0;
1002
1003         if (current_euid() == current_uid() && current_egid() == current_gid())
1004                 set_dumpable(current->mm, 1);
1005         else
1006                 set_dumpable(current->mm, suid_dumpable);
1007
1008         name = bprm->filename;
1009
1010         /* Copies the binary name from after last slash */
1011         for (i=0; (ch = *(name++)) != '\0';) {
1012                 if (ch == '/')
1013                         i = 0; /* overwrite what we wrote */
1014                 else
1015                         if (i < (sizeof(tcomm) - 1))
1016                                 tcomm[i++] = ch;
1017         }
1018         tcomm[i] = '\0';
1019         set_task_comm(current, tcomm);
1020
1021         /* Set the new mm task size. We have to do that late because it may
1022          * depend on TIF_32BIT which is only updated in flush_thread() on
1023          * some architectures like powerpc
1024          */
1025         current->mm->task_size = TASK_SIZE;
1026
1027         /* install the new credentials */
1028         if (bprm->cred->uid != current_euid() ||
1029             bprm->cred->gid != current_egid()) {
1030                 current->pdeath_signal = 0;
1031         } else if (file_permission(bprm->file, MAY_READ) ||
1032                    bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) {
1033                 set_dumpable(current->mm, suid_dumpable);
1034         }
1035
1036         /*
1037          * Flush performance counters when crossing a
1038          * security domain:
1039          */
1040         if (!get_dumpable(current->mm))
1041                 perf_event_exit_task(current);
1042
1043         /* An exec changes our domain. We are no longer part of the thread
1044            group */
1045
1046         current->self_exec_id++;
1047                         
1048         flush_signal_handlers(current, 0);
1049         flush_old_files(current->files);
1050 }
1051 EXPORT_SYMBOL(setup_new_exec);
1052
1053 /*
1054  * Prepare credentials and lock ->cred_guard_mutex.
1055  * install_exec_creds() commits the new creds and drops the lock.
1056  * Or, if exec fails before, free_bprm() should release ->cred and
1057  * and unlock.
1058  */
1059 int prepare_bprm_creds(struct linux_binprm *bprm)
1060 {
1061         if (mutex_lock_interruptible(&current->cred_guard_mutex))
1062                 return -ERESTARTNOINTR;
1063
1064         bprm->cred = prepare_exec_creds();
1065         if (likely(bprm->cred))
1066                 return 0;
1067
1068         mutex_unlock(&current->cred_guard_mutex);
1069         return -ENOMEM;
1070 }
1071
1072 void free_bprm(struct linux_binprm *bprm)
1073 {
1074         free_arg_pages(bprm);
1075         if (bprm->cred) {
1076                 mutex_unlock(&current->cred_guard_mutex);
1077                 abort_creds(bprm->cred);
1078         }
1079         kfree(bprm);
1080 }
1081
1082 /*
1083  * install the new credentials for this executable
1084  */
1085 void install_exec_creds(struct linux_binprm *bprm)
1086 {
1087         security_bprm_committing_creds(bprm);
1088
1089         commit_creds(bprm->cred);
1090         bprm->cred = NULL;
1091         /*
1092          * cred_guard_mutex must be held at least to this point to prevent
1093          * ptrace_attach() from altering our determination of the task's
1094          * credentials; any time after this it may be unlocked.
1095          */
1096         security_bprm_committed_creds(bprm);
1097         mutex_unlock(&current->cred_guard_mutex);
1098 }
1099 EXPORT_SYMBOL(install_exec_creds);
1100
1101 /*
1102  * determine how safe it is to execute the proposed program
1103  * - the caller must hold current->cred_guard_mutex to protect against
1104  *   PTRACE_ATTACH
1105  */
1106 int check_unsafe_exec(struct linux_binprm *bprm)
1107 {
1108         struct task_struct *p = current, *t;
1109         unsigned n_fs;
1110         int res = 0;
1111
1112         bprm->unsafe = tracehook_unsafe_exec(p);
1113
1114         n_fs = 1;
1115         write_lock(&p->fs->lock);
1116         rcu_read_lock();
1117         for (t = next_thread(p); t != p; t = next_thread(t)) {
1118                 if (t->fs == p->fs)
1119                         n_fs++;
1120         }
1121         rcu_read_unlock();
1122
1123         if (p->fs->users > n_fs) {
1124                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1125         } else {
1126                 res = -EAGAIN;
1127                 if (!p->fs->in_exec) {
1128                         p->fs->in_exec = 1;
1129                         res = 1;
1130                 }
1131         }
1132         write_unlock(&p->fs->lock);
1133
1134         return res;
1135 }
1136
1137 /* 
1138  * Fill the binprm structure from the inode. 
1139  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1140  *
1141  * This may be called multiple times for binary chains (scripts for example).
1142  */
1143 int prepare_binprm(struct linux_binprm *bprm)
1144 {
1145         umode_t mode;
1146         struct inode * inode = bprm->file->f_path.dentry->d_inode;
1147         int retval;
1148
1149         mode = inode->i_mode;
1150         if (bprm->file->f_op == NULL)
1151                 return -EACCES;
1152
1153         /* clear any previous set[ug]id data from a previous binary */
1154         bprm->cred->euid = current_euid();
1155         bprm->cred->egid = current_egid();
1156
1157         if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
1158                 /* Set-uid? */
1159                 if (mode & S_ISUID) {
1160                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1161                         bprm->cred->euid = inode->i_uid;
1162                 }
1163
1164                 /* Set-gid? */
1165                 /*
1166                  * If setgid is set but no group execute bit then this
1167                  * is a candidate for mandatory locking, not a setgid
1168                  * executable.
1169                  */
1170                 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1171                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1172                         bprm->cred->egid = inode->i_gid;
1173                 }
1174         }
1175
1176         /* fill in binprm security blob */
1177         retval = security_bprm_set_creds(bprm);
1178         if (retval)
1179                 return retval;
1180         bprm->cred_prepared = 1;
1181
1182         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1183         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1184 }
1185
1186 EXPORT_SYMBOL(prepare_binprm);
1187
1188 /*
1189  * Arguments are '\0' separated strings found at the location bprm->p
1190  * points to; chop off the first by relocating brpm->p to right after
1191  * the first '\0' encountered.
1192  */
1193 int remove_arg_zero(struct linux_binprm *bprm)
1194 {
1195         int ret = 0;
1196         unsigned long offset;
1197         char *kaddr;
1198         struct page *page;
1199
1200         if (!bprm->argc)
1201                 return 0;
1202
1203         do {
1204                 offset = bprm->p & ~PAGE_MASK;
1205                 page = get_arg_page(bprm, bprm->p, 0);
1206                 if (!page) {
1207                         ret = -EFAULT;
1208                         goto out;
1209                 }
1210                 kaddr = kmap_atomic(page, KM_USER0);
1211
1212                 for (; offset < PAGE_SIZE && kaddr[offset];
1213                                 offset++, bprm->p++)
1214                         ;
1215
1216                 kunmap_atomic(kaddr, KM_USER0);
1217                 put_arg_page(page);
1218
1219                 if (offset == PAGE_SIZE)
1220                         free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1221         } while (offset == PAGE_SIZE);
1222
1223         bprm->p++;
1224         bprm->argc--;
1225         ret = 0;
1226
1227 out:
1228         return ret;
1229 }
1230 EXPORT_SYMBOL(remove_arg_zero);
1231
1232 /*
1233  * cycle the list of binary formats handler, until one recognizes the image
1234  */
1235 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1236 {
1237         unsigned int depth = bprm->recursion_depth;
1238         int try,retval;
1239         struct linux_binfmt *fmt;
1240
1241         retval = security_bprm_check(bprm);
1242         if (retval)
1243                 return retval;
1244
1245         /* kernel module loader fixup */
1246         /* so we don't try to load run modprobe in kernel space. */
1247         set_fs(USER_DS);
1248
1249         retval = audit_bprm(bprm);
1250         if (retval)
1251                 return retval;
1252
1253         retval = -ENOENT;
1254         for (try=0; try<2; try++) {
1255                 read_lock(&binfmt_lock);
1256                 list_for_each_entry(fmt, &formats, lh) {
1257                         int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1258                         if (!fn)
1259                                 continue;
1260                         if (!try_module_get(fmt->module))
1261                                 continue;
1262                         read_unlock(&binfmt_lock);
1263                         retval = fn(bprm, regs);
1264                         /*
1265                          * Restore the depth counter to its starting value
1266                          * in this call, so we don't have to rely on every
1267                          * load_binary function to restore it on return.
1268                          */
1269                         bprm->recursion_depth = depth;
1270                         if (retval >= 0) {
1271                                 if (depth == 0)
1272                                         tracehook_report_exec(fmt, bprm, regs);
1273                                 put_binfmt(fmt);
1274                                 allow_write_access(bprm->file);
1275                                 if (bprm->file)
1276                                         fput(bprm->file);
1277                                 bprm->file = NULL;
1278                                 current->did_exec = 1;
1279                                 proc_exec_connector(current);
1280                                 return retval;
1281                         }
1282                         read_lock(&binfmt_lock);
1283                         put_binfmt(fmt);
1284                         if (retval != -ENOEXEC || bprm->mm == NULL)
1285                                 break;
1286                         if (!bprm->file) {
1287                                 read_unlock(&binfmt_lock);
1288                                 return retval;
1289                         }
1290                 }
1291                 read_unlock(&binfmt_lock);
1292                 if (retval != -ENOEXEC || bprm->mm == NULL) {
1293                         break;
1294 #ifdef CONFIG_MODULES
1295                 } else {
1296 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1297                         if (printable(bprm->buf[0]) &&
1298                             printable(bprm->buf[1]) &&
1299                             printable(bprm->buf[2]) &&
1300                             printable(bprm->buf[3]))
1301                                 break; /* -ENOEXEC */
1302                         request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1303 #endif
1304                 }
1305         }
1306         return retval;
1307 }
1308
1309 EXPORT_SYMBOL(search_binary_handler);
1310
1311 /*
1312  * sys_execve() executes a new program.
1313  */
1314 int do_execve(char * filename,
1315         char __user *__user *argv,
1316         char __user *__user *envp,
1317         struct pt_regs * regs)
1318 {
1319         struct linux_binprm *bprm;
1320         struct file *file;
1321         struct files_struct *displaced;
1322         bool clear_in_exec;
1323         int retval;
1324
1325         retval = unshare_files(&displaced);
1326         if (retval)
1327                 goto out_ret;
1328
1329         retval = -ENOMEM;
1330         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1331         if (!bprm)
1332                 goto out_files;
1333
1334         retval = prepare_bprm_creds(bprm);
1335         if (retval)
1336                 goto out_free;
1337
1338         retval = check_unsafe_exec(bprm);
1339         if (retval < 0)
1340                 goto out_free;
1341         clear_in_exec = retval;
1342         current->in_execve = 1;
1343
1344         file = open_exec(filename);
1345         retval = PTR_ERR(file);
1346         if (IS_ERR(file))
1347                 goto out_unmark;
1348
1349         sched_exec();
1350
1351         bprm->file = file;
1352         bprm->filename = filename;
1353         bprm->interp = filename;
1354
1355         retval = bprm_mm_init(bprm);
1356         if (retval)
1357                 goto out_file;
1358
1359         bprm->argc = count(argv, MAX_ARG_STRINGS);
1360         if ((retval = bprm->argc) < 0)
1361                 goto out;
1362
1363         bprm->envc = count(envp, MAX_ARG_STRINGS);
1364         if ((retval = bprm->envc) < 0)
1365                 goto out;
1366
1367         retval = prepare_binprm(bprm);
1368         if (retval < 0)
1369                 goto out;
1370
1371         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1372         if (retval < 0)
1373                 goto out;
1374
1375         bprm->exec = bprm->p;
1376         retval = copy_strings(bprm->envc, envp, bprm);
1377         if (retval < 0)
1378                 goto out;
1379
1380         retval = copy_strings(bprm->argc, argv, bprm);
1381         if (retval < 0)
1382                 goto out;
1383
1384         current->flags &= ~PF_KTHREAD;
1385         retval = search_binary_handler(bprm,regs);
1386         if (retval < 0)
1387                 goto out;
1388
1389         current->stack_start = current->mm->start_stack;
1390
1391         /* execve succeeded */
1392         current->fs->in_exec = 0;
1393         current->in_execve = 0;
1394         acct_update_integrals(current);
1395         free_bprm(bprm);
1396         if (displaced)
1397                 put_files_struct(displaced);
1398         return retval;
1399
1400 out:
1401         if (bprm->mm)
1402                 mmput (bprm->mm);
1403
1404 out_file:
1405         if (bprm->file) {
1406                 allow_write_access(bprm->file);
1407                 fput(bprm->file);
1408         }
1409
1410 out_unmark:
1411         if (clear_in_exec)
1412                 current->fs->in_exec = 0;
1413         current->in_execve = 0;
1414
1415 out_free:
1416         free_bprm(bprm);
1417
1418 out_files:
1419         if (displaced)
1420                 reset_files_struct(displaced);
1421 out_ret:
1422         return retval;
1423 }
1424
1425 void set_binfmt(struct linux_binfmt *new)
1426 {
1427         struct mm_struct *mm = current->mm;
1428
1429         if (mm->binfmt)
1430                 module_put(mm->binfmt->module);
1431
1432         mm->binfmt = new;
1433         if (new)
1434                 __module_get(new->module);
1435 }
1436
1437 EXPORT_SYMBOL(set_binfmt);
1438
1439 /* format_corename will inspect the pattern parameter, and output a
1440  * name into corename, which must have space for at least
1441  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
1442  */
1443 static int format_corename(char *corename, long signr)
1444 {
1445         const struct cred *cred = current_cred();
1446         const char *pat_ptr = core_pattern;
1447         int ispipe = (*pat_ptr == '|');
1448         char *out_ptr = corename;
1449         char *const out_end = corename + CORENAME_MAX_SIZE;
1450         int rc;
1451         int pid_in_pattern = 0;
1452
1453         /* Repeat as long as we have more pattern to process and more output
1454            space */
1455         while (*pat_ptr) {
1456                 if (*pat_ptr != '%') {
1457                         if (out_ptr == out_end)
1458                                 goto out;
1459                         *out_ptr++ = *pat_ptr++;
1460                 } else {
1461                         switch (*++pat_ptr) {
1462                         case 0:
1463                                 goto out;
1464                         /* Double percent, output one percent */
1465                         case '%':
1466                                 if (out_ptr == out_end)
1467                                         goto out;
1468                                 *out_ptr++ = '%';
1469                                 break;
1470                         /* pid */
1471                         case 'p':
1472                                 pid_in_pattern = 1;
1473                                 rc = snprintf(out_ptr, out_end - out_ptr,
1474                                               "%d", task_tgid_vnr(current));
1475                                 if (rc > out_end - out_ptr)
1476                                         goto out;
1477                                 out_ptr += rc;
1478                                 break;
1479                         /* uid */
1480                         case 'u':
1481                                 rc = snprintf(out_ptr, out_end - out_ptr,
1482                                               "%d", cred->uid);
1483                                 if (rc > out_end - out_ptr)
1484                                         goto out;
1485                                 out_ptr += rc;
1486                                 break;
1487                         /* gid */
1488                         case 'g':
1489                                 rc = snprintf(out_ptr, out_end - out_ptr,
1490                                               "%d", cred->gid);
1491                                 if (rc > out_end - out_ptr)
1492                                         goto out;
1493                                 out_ptr += rc;
1494                                 break;
1495                         /* signal that caused the coredump */
1496                         case 's':
1497                                 rc = snprintf(out_ptr, out_end - out_ptr,
1498                                               "%ld", signr);
1499                                 if (rc > out_end - out_ptr)
1500                                         goto out;
1501                                 out_ptr += rc;
1502                                 break;
1503                         /* UNIX time of coredump */
1504                         case 't': {
1505                                 struct timeval tv;
1506                                 do_gettimeofday(&tv);
1507                                 rc = snprintf(out_ptr, out_end - out_ptr,
1508                                               "%lu", tv.tv_sec);
1509                                 if (rc > out_end - out_ptr)
1510                                         goto out;
1511                                 out_ptr += rc;
1512                                 break;
1513                         }
1514                         /* hostname */
1515                         case 'h':
1516                                 down_read(&uts_sem);
1517                                 rc = snprintf(out_ptr, out_end - out_ptr,
1518                                               "%s", utsname()->nodename);
1519                                 up_read(&uts_sem);
1520                                 if (rc > out_end - out_ptr)
1521                                         goto out;
1522                                 out_ptr += rc;
1523                                 break;
1524                         /* executable */
1525                         case 'e':
1526                                 rc = snprintf(out_ptr, out_end - out_ptr,
1527                                               "%s", current->comm);
1528                                 if (rc > out_end - out_ptr)
1529                                         goto out;
1530                                 out_ptr += rc;
1531                                 break;
1532                         /* core limit size */
1533                         case 'c':
1534                                 rc = snprintf(out_ptr, out_end - out_ptr,
1535                                               "%lu", current->signal->rlim[RLIMIT_CORE].rlim_cur);
1536                                 if (rc > out_end - out_ptr)
1537                                         goto out;
1538                                 out_ptr += rc;
1539                                 break;
1540                         default:
1541                                 break;
1542                         }
1543                         ++pat_ptr;
1544                 }
1545         }
1546         /* Backward compatibility with core_uses_pid:
1547          *
1548          * If core_pattern does not include a %p (as is the default)
1549          * and core_uses_pid is set, then .%pid will be appended to
1550          * the filename. Do not do this for piped commands. */
1551         if (!ispipe && !pid_in_pattern && core_uses_pid) {
1552                 rc = snprintf(out_ptr, out_end - out_ptr,
1553                               ".%d", task_tgid_vnr(current));
1554                 if (rc > out_end - out_ptr)
1555                         goto out;
1556                 out_ptr += rc;
1557         }
1558 out:
1559         *out_ptr = 0;
1560         return ispipe;
1561 }
1562
1563 static int zap_process(struct task_struct *start)
1564 {
1565         struct task_struct *t;
1566         int nr = 0;
1567
1568         start->signal->flags = SIGNAL_GROUP_EXIT;
1569         start->signal->group_stop_count = 0;
1570
1571         t = start;
1572         do {
1573                 if (t != current && t->mm) {
1574                         sigaddset(&t->pending.signal, SIGKILL);
1575                         signal_wake_up(t, 1);
1576                         nr++;
1577                 }
1578         } while_each_thread(start, t);
1579
1580         return nr;
1581 }
1582
1583 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
1584                                 struct core_state *core_state, int exit_code)
1585 {
1586         struct task_struct *g, *p;
1587         unsigned long flags;
1588         int nr = -EAGAIN;
1589
1590         spin_lock_irq(&tsk->sighand->siglock);
1591         if (!signal_group_exit(tsk->signal)) {
1592                 mm->core_state = core_state;
1593                 tsk->signal->group_exit_code = exit_code;
1594                 nr = zap_process(tsk);
1595         }
1596         spin_unlock_irq(&tsk->sighand->siglock);
1597         if (unlikely(nr < 0))
1598                 return nr;
1599
1600         if (atomic_read(&mm->mm_users) == nr + 1)
1601                 goto done;
1602         /*
1603          * We should find and kill all tasks which use this mm, and we should
1604          * count them correctly into ->nr_threads. We don't take tasklist
1605          * lock, but this is safe wrt:
1606          *
1607          * fork:
1608          *      None of sub-threads can fork after zap_process(leader). All
1609          *      processes which were created before this point should be
1610          *      visible to zap_threads() because copy_process() adds the new
1611          *      process to the tail of init_task.tasks list, and lock/unlock
1612          *      of ->siglock provides a memory barrier.
1613          *
1614          * do_exit:
1615          *      The caller holds mm->mmap_sem. This means that the task which
1616          *      uses this mm can't pass exit_mm(), so it can't exit or clear
1617          *      its ->mm.
1618          *
1619          * de_thread:
1620          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
1621          *      we must see either old or new leader, this does not matter.
1622          *      However, it can change p->sighand, so lock_task_sighand(p)
1623          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
1624          *      it can't fail.
1625          *
1626          *      Note also that "g" can be the old leader with ->mm == NULL
1627          *      and already unhashed and thus removed from ->thread_group.
1628          *      This is OK, __unhash_process()->list_del_rcu() does not
1629          *      clear the ->next pointer, we will find the new leader via
1630          *      next_thread().
1631          */
1632         rcu_read_lock();
1633         for_each_process(g) {
1634                 if (g == tsk->group_leader)
1635                         continue;
1636                 if (g->flags & PF_KTHREAD)
1637                         continue;
1638                 p = g;
1639                 do {
1640                         if (p->mm) {
1641                                 if (unlikely(p->mm == mm)) {
1642                                         lock_task_sighand(p, &flags);
1643                                         nr += zap_process(p);
1644                                         unlock_task_sighand(p, &flags);
1645                                 }
1646                                 break;
1647                         }
1648                 } while_each_thread(g, p);
1649         }
1650         rcu_read_unlock();
1651 done:
1652         atomic_set(&core_state->nr_threads, nr);
1653         return nr;
1654 }
1655
1656 static int coredump_wait(int exit_code, struct core_state *core_state)
1657 {
1658         struct task_struct *tsk = current;
1659         struct mm_struct *mm = tsk->mm;
1660         struct completion *vfork_done;
1661         int core_waiters;
1662
1663         init_completion(&core_state->startup);
1664         core_state->dumper.task = tsk;
1665         core_state->dumper.next = NULL;
1666         core_waiters = zap_threads(tsk, mm, core_state, exit_code);
1667         up_write(&mm->mmap_sem);
1668
1669         if (unlikely(core_waiters < 0))
1670                 goto fail;
1671
1672         /*
1673          * Make sure nobody is waiting for us to release the VM,
1674          * otherwise we can deadlock when we wait on each other
1675          */
1676         vfork_done = tsk->vfork_done;
1677         if (vfork_done) {
1678                 tsk->vfork_done = NULL;
1679                 complete(vfork_done);
1680         }
1681
1682         if (core_waiters)
1683                 wait_for_completion(&core_state->startup);
1684 fail:
1685         return core_waiters;
1686 }
1687
1688 static void coredump_finish(struct mm_struct *mm)
1689 {
1690         struct core_thread *curr, *next;
1691         struct task_struct *task;
1692
1693         next = mm->core_state->dumper.next;
1694         while ((curr = next) != NULL) {
1695                 next = curr->next;
1696                 task = curr->task;
1697                 /*
1698                  * see exit_mm(), curr->task must not see
1699                  * ->task == NULL before we read ->next.
1700                  */
1701                 smp_mb();
1702                 curr->task = NULL;
1703                 wake_up_process(task);
1704         }
1705
1706         mm->core_state = NULL;
1707 }
1708
1709 /*
1710  * set_dumpable converts traditional three-value dumpable to two flags and
1711  * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
1712  * these bits are not changed atomically.  So get_dumpable can observe the
1713  * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
1714  * return either old dumpable or new one by paying attention to the order of
1715  * modifying the bits.
1716  *
1717  * dumpable |   mm->flags (binary)
1718  * old  new | initial interim  final
1719  * ---------+-----------------------
1720  *  0    1  |   00      01      01
1721  *  0    2  |   00      10(*)   11
1722  *  1    0  |   01      00      00
1723  *  1    2  |   01      11      11
1724  *  2    0  |   11      10(*)   00
1725  *  2    1  |   11      11      01
1726  *
1727  * (*) get_dumpable regards interim value of 10 as 11.
1728  */
1729 void set_dumpable(struct mm_struct *mm, int value)
1730 {
1731         switch (value) {
1732         case 0:
1733                 clear_bit(MMF_DUMPABLE, &mm->flags);
1734                 smp_wmb();
1735                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1736                 break;
1737         case 1:
1738                 set_bit(MMF_DUMPABLE, &mm->flags);
1739                 smp_wmb();
1740                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1741                 break;
1742         case 2:
1743                 set_bit(MMF_DUMP_SECURELY, &mm->flags);
1744                 smp_wmb();
1745                 set_bit(MMF_DUMPABLE, &mm->flags);
1746                 break;
1747         }
1748 }
1749
1750 int get_dumpable(struct mm_struct *mm)
1751 {
1752         int ret;
1753
1754         ret = mm->flags & 0x3;
1755         return (ret >= 2) ? 2 : ret;
1756 }
1757
1758 static void wait_for_dump_helpers(struct file *file)
1759 {
1760         struct pipe_inode_info *pipe;
1761
1762         pipe = file->f_path.dentry->d_inode->i_pipe;
1763
1764         pipe_lock(pipe);
1765         pipe->readers++;
1766         pipe->writers--;
1767
1768         while ((pipe->readers > 1) && (!signal_pending(current))) {
1769                 wake_up_interruptible_sync(&pipe->wait);
1770                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
1771                 pipe_wait(pipe);
1772         }
1773
1774         pipe->readers--;
1775         pipe->writers++;
1776         pipe_unlock(pipe);
1777
1778 }
1779
1780
1781 void do_coredump(long signr, int exit_code, struct pt_regs *regs)
1782 {
1783         struct core_state core_state;
1784         char corename[CORENAME_MAX_SIZE + 1];
1785         struct mm_struct *mm = current->mm;
1786         struct linux_binfmt * binfmt;
1787         struct inode * inode;
1788         const struct cred *old_cred;
1789         struct cred *cred;
1790         int retval = 0;
1791         int flag = 0;
1792         int ispipe = 0;
1793         char **helper_argv = NULL;
1794         int helper_argc = 0;
1795         int dump_count = 0;
1796         static atomic_t core_dump_count = ATOMIC_INIT(0);
1797         struct coredump_params cprm = {
1798                 .signr = signr,
1799                 .regs = regs,
1800                 .limit = current->signal->rlim[RLIMIT_CORE].rlim_cur,
1801         };
1802
1803         audit_core_dumps(signr);
1804
1805         binfmt = mm->binfmt;
1806         if (!binfmt || !binfmt->core_dump)
1807                 goto fail;
1808
1809         cred = prepare_creds();
1810         if (!cred) {
1811                 retval = -ENOMEM;
1812                 goto fail;
1813         }
1814
1815         down_write(&mm->mmap_sem);
1816         /*
1817          * If another thread got here first, or we are not dumpable, bail out.
1818          */
1819         if (mm->core_state || !get_dumpable(mm)) {
1820                 up_write(&mm->mmap_sem);
1821                 put_cred(cred);
1822                 goto fail;
1823         }
1824
1825         /*
1826          *      We cannot trust fsuid as being the "true" uid of the
1827          *      process nor do we know its entire history. We only know it
1828          *      was tainted so we dump it as root in mode 2.
1829          */
1830         if (get_dumpable(mm) == 2) {    /* Setuid core dump mode */
1831                 flag = O_EXCL;          /* Stop rewrite attacks */
1832                 cred->fsuid = 0;        /* Dump root private */
1833         }
1834
1835         retval = coredump_wait(exit_code, &core_state);
1836         if (retval < 0) {
1837                 put_cred(cred);
1838                 goto fail;
1839         }
1840
1841         old_cred = override_creds(cred);
1842
1843         /*
1844          * Clear any false indication of pending signals that might
1845          * be seen by the filesystem code called to write the core file.
1846          */
1847         clear_thread_flag(TIF_SIGPENDING);
1848
1849         /*
1850          * lock_kernel() because format_corename() is controlled by sysctl, which
1851          * uses lock_kernel()
1852          */
1853         lock_kernel();
1854         ispipe = format_corename(corename, signr);
1855         unlock_kernel();
1856
1857         if ((!ispipe) && (cprm.limit < binfmt->min_coredump))
1858                 goto fail_unlock;
1859
1860         if (ispipe) {
1861                 if (cprm.limit == 0) {
1862                         /*
1863                          * Normally core limits are irrelevant to pipes, since
1864                          * we're not writing to the file system, but we use
1865                          * cprm.limit of 0 here as a speacial value. Any
1866                          * non-zero limit gets set to RLIM_INFINITY below, but
1867                          * a limit of 0 skips the dump.  This is a consistent
1868                          * way to catch recursive crashes.  We can still crash
1869                          * if the core_pattern binary sets RLIM_CORE =  !0
1870                          * but it runs as root, and can do lots of stupid things
1871                          * Note that we use task_tgid_vnr here to grab the pid
1872                          * of the process group leader.  That way we get the
1873                          * right pid if a thread in a multi-threaded
1874                          * core_pattern process dies.
1875                          */
1876                         printk(KERN_WARNING
1877                                 "Process %d(%s) has RLIMIT_CORE set to 0\n",
1878                                 task_tgid_vnr(current), current->comm);
1879                         printk(KERN_WARNING "Aborting core\n");
1880                         goto fail_unlock;
1881                 }
1882
1883                 dump_count = atomic_inc_return(&core_dump_count);
1884                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
1885                         printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
1886                                task_tgid_vnr(current), current->comm);
1887                         printk(KERN_WARNING "Skipping core dump\n");
1888                         goto fail_dropcount;
1889                 }
1890
1891                 helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc);
1892                 if (!helper_argv) {
1893                         printk(KERN_WARNING "%s failed to allocate memory\n",
1894                                __func__);
1895                         goto fail_dropcount;
1896                 }
1897
1898                 cprm.limit = RLIM_INFINITY;
1899
1900                 /* SIGPIPE can happen, but it's just never processed */
1901                 if (call_usermodehelper_pipe(helper_argv[0], helper_argv, NULL,
1902                                 &cprm.file)) {
1903                         printk(KERN_INFO "Core dump to %s pipe failed\n",
1904                                corename);
1905                         goto fail_dropcount;
1906                 }
1907         } else
1908                 cprm.file = filp_open(corename,
1909                                  O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
1910                                  0600);
1911         if (IS_ERR(cprm.file))
1912                 goto fail_dropcount;
1913         inode = cprm.file->f_path.dentry->d_inode;
1914         if (inode->i_nlink > 1)
1915                 goto close_fail;        /* multiple links - don't dump */
1916         if (!ispipe && d_unhashed(cprm.file->f_path.dentry))
1917                 goto close_fail;
1918
1919         /* AK: actually i see no reason to not allow this for named pipes etc.,
1920            but keep the previous behaviour for now. */
1921         if (!ispipe && !S_ISREG(inode->i_mode))
1922                 goto close_fail;
1923         /*
1924          * Dont allow local users get cute and trick others to coredump
1925          * into their pre-created files:
1926          */
1927         if (inode->i_uid != current_fsuid())
1928                 goto close_fail;
1929         if (!cprm.file->f_op)
1930                 goto close_fail;
1931         if (!cprm.file->f_op->write)
1932                 goto close_fail;
1933         if (!ispipe &&
1934             do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file) != 0)
1935                 goto close_fail;
1936
1937         retval = binfmt->core_dump(&cprm);
1938
1939         if (retval)
1940                 current->signal->group_exit_code |= 0x80;
1941 close_fail:
1942         if (ispipe && core_pipe_limit)
1943                 wait_for_dump_helpers(cprm.file);
1944         filp_close(cprm.file, NULL);
1945 fail_dropcount:
1946         if (dump_count)
1947                 atomic_dec(&core_dump_count);
1948 fail_unlock:
1949         if (helper_argv)
1950                 argv_free(helper_argv);
1951
1952         revert_creds(old_cred);
1953         put_cred(cred);
1954         coredump_finish(mm);
1955 fail:
1956         return;
1957 }