signals: move cred_guard_mutex from task_struct to signal_struct
[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/swap.h>
32 #include <linux/string.h>
33 #include <linux/init.h>
34 #include <linux/pagemap.h>
35 #include <linux/perf_event.h>
36 #include <linux/highmem.h>
37 #include <linux/spinlock.h>
38 #include <linux/key.h>
39 #include <linux/personality.h>
40 #include <linux/binfmts.h>
41 #include <linux/utsname.h>
42 #include <linux/pid_namespace.h>
43 #include <linux/module.h>
44 #include <linux/namei.h>
45 #include <linux/proc_fs.h>
46 #include <linux/mount.h>
47 #include <linux/security.h>
48 #include <linux/syscalls.h>
49 #include <linux/tsacct_kern.h>
50 #include <linux/cn_proc.h>
51 #include <linux/audit.h>
52 #include <linux/tracehook.h>
53 #include <linux/kmod.h>
54 #include <linux/fsnotify.h>
55 #include <linux/fs_struct.h>
56 #include <linux/pipe_fs_i.h>
57 #include <linux/oom.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);
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 > ACCESS_ONCE(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         BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
246         vma->vm_end = STACK_TOP_MAX;
247         vma->vm_start = vma->vm_end - PAGE_SIZE;
248         vma->vm_flags = VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
249         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
250         INIT_LIST_HEAD(&vma->anon_vma_chain);
251         err = insert_vm_struct(mm, vma);
252         if (err)
253                 goto err;
254
255         mm->stack_vm = mm->total_vm = 1;
256         up_write(&mm->mmap_sem);
257         bprm->p = vma->vm_end - sizeof(void *);
258         return 0;
259 err:
260         up_write(&mm->mmap_sem);
261         bprm->vma = NULL;
262         kmem_cache_free(vm_area_cachep, vma);
263         return err;
264 }
265
266 static bool valid_arg_len(struct linux_binprm *bprm, long len)
267 {
268         return len <= MAX_ARG_STRLEN;
269 }
270
271 #else
272
273 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
274                 int write)
275 {
276         struct page *page;
277
278         page = bprm->page[pos / PAGE_SIZE];
279         if (!page && write) {
280                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
281                 if (!page)
282                         return NULL;
283                 bprm->page[pos / PAGE_SIZE] = page;
284         }
285
286         return page;
287 }
288
289 static void put_arg_page(struct page *page)
290 {
291 }
292
293 static void free_arg_page(struct linux_binprm *bprm, int i)
294 {
295         if (bprm->page[i]) {
296                 __free_page(bprm->page[i]);
297                 bprm->page[i] = NULL;
298         }
299 }
300
301 static void free_arg_pages(struct linux_binprm *bprm)
302 {
303         int i;
304
305         for (i = 0; i < MAX_ARG_PAGES; i++)
306                 free_arg_page(bprm, i);
307 }
308
309 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
310                 struct page *page)
311 {
312 }
313
314 static int __bprm_mm_init(struct linux_binprm *bprm)
315 {
316         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
317         return 0;
318 }
319
320 static bool valid_arg_len(struct linux_binprm *bprm, long len)
321 {
322         return len <= bprm->p;
323 }
324
325 #endif /* CONFIG_MMU */
326
327 /*
328  * Create a new mm_struct and populate it with a temporary stack
329  * vm_area_struct.  We don't have enough context at this point to set the stack
330  * flags, permissions, and offset, so we use temporary values.  We'll update
331  * them later in setup_arg_pages().
332  */
333 int bprm_mm_init(struct linux_binprm *bprm)
334 {
335         int err;
336         struct mm_struct *mm = NULL;
337
338         bprm->mm = mm = mm_alloc();
339         err = -ENOMEM;
340         if (!mm)
341                 goto err;
342
343         err = init_new_context(current, mm);
344         if (err)
345                 goto err;
346
347         err = __bprm_mm_init(bprm);
348         if (err)
349                 goto err;
350
351         return 0;
352
353 err:
354         if (mm) {
355                 bprm->mm = NULL;
356                 mmdrop(mm);
357         }
358
359         return err;
360 }
361
362 /*
363  * count() counts the number of strings in array ARGV.
364  */
365 static int count(const char __user * const __user * argv, int max)
366 {
367         int i = 0;
368
369         if (argv != NULL) {
370                 for (;;) {
371                         const char __user * p;
372
373                         if (get_user(p, argv))
374                                 return -EFAULT;
375                         if (!p)
376                                 break;
377                         argv++;
378                         if (i++ >= max)
379                                 return -E2BIG;
380
381                         if (fatal_signal_pending(current))
382                                 return -ERESTARTNOHAND;
383                         cond_resched();
384                 }
385         }
386         return i;
387 }
388
389 /*
390  * 'copy_strings()' copies argument/environment strings from the old
391  * processes's memory to the new process's stack.  The call to get_user_pages()
392  * ensures the destination page is created and not swapped out.
393  */
394 static int copy_strings(int argc, const char __user *const __user *argv,
395                         struct linux_binprm *bprm)
396 {
397         struct page *kmapped_page = NULL;
398         char *kaddr = NULL;
399         unsigned long kpos = 0;
400         int ret;
401
402         while (argc-- > 0) {
403                 const char __user *str;
404                 int len;
405                 unsigned long pos;
406
407                 if (get_user(str, argv+argc) ||
408                                 !(len = strnlen_user(str, MAX_ARG_STRLEN))) {
409                         ret = -EFAULT;
410                         goto out;
411                 }
412
413                 if (!valid_arg_len(bprm, len)) {
414                         ret = -E2BIG;
415                         goto out;
416                 }
417
418                 /* We're going to work our way backwords. */
419                 pos = bprm->p;
420                 str += len;
421                 bprm->p -= len;
422
423                 while (len > 0) {
424                         int offset, bytes_to_copy;
425
426                         if (fatal_signal_pending(current)) {
427                                 ret = -ERESTARTNOHAND;
428                                 goto out;
429                         }
430                         cond_resched();
431
432                         offset = pos % PAGE_SIZE;
433                         if (offset == 0)
434                                 offset = PAGE_SIZE;
435
436                         bytes_to_copy = offset;
437                         if (bytes_to_copy > len)
438                                 bytes_to_copy = len;
439
440                         offset -= bytes_to_copy;
441                         pos -= bytes_to_copy;
442                         str -= bytes_to_copy;
443                         len -= bytes_to_copy;
444
445                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
446                                 struct page *page;
447
448                                 page = get_arg_page(bprm, pos, 1);
449                                 if (!page) {
450                                         ret = -E2BIG;
451                                         goto out;
452                                 }
453
454                                 if (kmapped_page) {
455                                         flush_kernel_dcache_page(kmapped_page);
456                                         kunmap(kmapped_page);
457                                         put_arg_page(kmapped_page);
458                                 }
459                                 kmapped_page = page;
460                                 kaddr = kmap(kmapped_page);
461                                 kpos = pos & PAGE_MASK;
462                                 flush_arg_page(bprm, kpos, kmapped_page);
463                         }
464                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
465                                 ret = -EFAULT;
466                                 goto out;
467                         }
468                 }
469         }
470         ret = 0;
471 out:
472         if (kmapped_page) {
473                 flush_kernel_dcache_page(kmapped_page);
474                 kunmap(kmapped_page);
475                 put_arg_page(kmapped_page);
476         }
477         return ret;
478 }
479
480 /*
481  * Like copy_strings, but get argv and its values from kernel memory.
482  */
483 int copy_strings_kernel(int argc, const char *const *argv,
484                         struct linux_binprm *bprm)
485 {
486         int r;
487         mm_segment_t oldfs = get_fs();
488         set_fs(KERNEL_DS);
489         r = copy_strings(argc, (const char __user *const  __user *)argv, bprm);
490         set_fs(oldfs);
491         return r;
492 }
493 EXPORT_SYMBOL(copy_strings_kernel);
494
495 #ifdef CONFIG_MMU
496
497 /*
498  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
499  * the binfmt code determines where the new stack should reside, we shift it to
500  * its final location.  The process proceeds as follows:
501  *
502  * 1) Use shift to calculate the new vma endpoints.
503  * 2) Extend vma to cover both the old and new ranges.  This ensures the
504  *    arguments passed to subsequent functions are consistent.
505  * 3) Move vma's page tables to the new range.
506  * 4) Free up any cleared pgd range.
507  * 5) Shrink the vma to cover only the new range.
508  */
509 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
510 {
511         struct mm_struct *mm = vma->vm_mm;
512         unsigned long old_start = vma->vm_start;
513         unsigned long old_end = vma->vm_end;
514         unsigned long length = old_end - old_start;
515         unsigned long new_start = old_start - shift;
516         unsigned long new_end = old_end - shift;
517         struct mmu_gather *tlb;
518
519         BUG_ON(new_start > new_end);
520
521         /*
522          * ensure there are no vmas between where we want to go
523          * and where we are
524          */
525         if (vma != find_vma(mm, new_start))
526                 return -EFAULT;
527
528         /*
529          * cover the whole range: [new_start, old_end)
530          */
531         if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
532                 return -ENOMEM;
533
534         /*
535          * move the page tables downwards, on failure we rely on
536          * process cleanup to remove whatever mess we made.
537          */
538         if (length != move_page_tables(vma, old_start,
539                                        vma, new_start, length))
540                 return -ENOMEM;
541
542         lru_add_drain();
543         tlb = tlb_gather_mmu(mm, 0);
544         if (new_end > old_start) {
545                 /*
546                  * when the old and new regions overlap clear from new_end.
547                  */
548                 free_pgd_range(tlb, new_end, old_end, new_end,
549                         vma->vm_next ? vma->vm_next->vm_start : 0);
550         } else {
551                 /*
552                  * otherwise, clean from old_start; this is done to not touch
553                  * the address space in [new_end, old_start) some architectures
554                  * have constraints on va-space that make this illegal (IA64) -
555                  * for the others its just a little faster.
556                  */
557                 free_pgd_range(tlb, old_start, old_end, new_end,
558                         vma->vm_next ? vma->vm_next->vm_start : 0);
559         }
560         tlb_finish_mmu(tlb, new_end, old_end);
561
562         /*
563          * Shrink the vma to just the new range.  Always succeeds.
564          */
565         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
566
567         return 0;
568 }
569
570 /*
571  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
572  * the stack is optionally relocated, and some extra space is added.
573  */
574 int setup_arg_pages(struct linux_binprm *bprm,
575                     unsigned long stack_top,
576                     int executable_stack)
577 {
578         unsigned long ret;
579         unsigned long stack_shift;
580         struct mm_struct *mm = current->mm;
581         struct vm_area_struct *vma = bprm->vma;
582         struct vm_area_struct *prev = NULL;
583         unsigned long vm_flags;
584         unsigned long stack_base;
585         unsigned long stack_size;
586         unsigned long stack_expand;
587         unsigned long rlim_stack;
588
589 #ifdef CONFIG_STACK_GROWSUP
590         /* Limit stack size to 1GB */
591         stack_base = rlimit_max(RLIMIT_STACK);
592         if (stack_base > (1 << 30))
593                 stack_base = 1 << 30;
594
595         /* Make sure we didn't let the argument array grow too large. */
596         if (vma->vm_end - vma->vm_start > stack_base)
597                 return -ENOMEM;
598
599         stack_base = PAGE_ALIGN(stack_top - stack_base);
600
601         stack_shift = vma->vm_start - stack_base;
602         mm->arg_start = bprm->p - stack_shift;
603         bprm->p = vma->vm_end - stack_shift;
604 #else
605         stack_top = arch_align_stack(stack_top);
606         stack_top = PAGE_ALIGN(stack_top);
607
608         if (unlikely(stack_top < mmap_min_addr) ||
609             unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
610                 return -ENOMEM;
611
612         stack_shift = vma->vm_end - stack_top;
613
614         bprm->p -= stack_shift;
615         mm->arg_start = bprm->p;
616 #endif
617
618         if (bprm->loader)
619                 bprm->loader -= stack_shift;
620         bprm->exec -= stack_shift;
621
622         down_write(&mm->mmap_sem);
623         vm_flags = VM_STACK_FLAGS;
624
625         /*
626          * Adjust stack execute permissions; explicitly enable for
627          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
628          * (arch default) otherwise.
629          */
630         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
631                 vm_flags |= VM_EXEC;
632         else if (executable_stack == EXSTACK_DISABLE_X)
633                 vm_flags &= ~VM_EXEC;
634         vm_flags |= mm->def_flags;
635         vm_flags |= VM_STACK_INCOMPLETE_SETUP;
636
637         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
638                         vm_flags);
639         if (ret)
640                 goto out_unlock;
641         BUG_ON(prev != vma);
642
643         /* Move stack pages down in memory. */
644         if (stack_shift) {
645                 ret = shift_arg_pages(vma, stack_shift);
646                 if (ret)
647                         goto out_unlock;
648         }
649
650         /* mprotect_fixup is overkill to remove the temporary stack flags */
651         vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
652
653         stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
654         stack_size = vma->vm_end - vma->vm_start;
655         /*
656          * Align this down to a page boundary as expand_stack
657          * will align it up.
658          */
659         rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
660 #ifdef CONFIG_STACK_GROWSUP
661         if (stack_size + stack_expand > rlim_stack)
662                 stack_base = vma->vm_start + rlim_stack;
663         else
664                 stack_base = vma->vm_end + stack_expand;
665 #else
666         if (stack_size + stack_expand > rlim_stack)
667                 stack_base = vma->vm_end - rlim_stack;
668         else
669                 stack_base = vma->vm_start - stack_expand;
670 #endif
671         current->mm->start_stack = bprm->p;
672         ret = expand_stack(vma, stack_base);
673         if (ret)
674                 ret = -EFAULT;
675
676 out_unlock:
677         up_write(&mm->mmap_sem);
678         return ret;
679 }
680 EXPORT_SYMBOL(setup_arg_pages);
681
682 #endif /* CONFIG_MMU */
683
684 struct file *open_exec(const char *name)
685 {
686         struct file *file;
687         int err;
688
689         file = do_filp_open(AT_FDCWD, name,
690                                 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0,
691                                 MAY_EXEC | MAY_OPEN);
692         if (IS_ERR(file))
693                 goto out;
694
695         err = -EACCES;
696         if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
697                 goto exit;
698
699         if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
700                 goto exit;
701
702         fsnotify_open(file);
703
704         err = deny_write_access(file);
705         if (err)
706                 goto exit;
707
708 out:
709         return file;
710
711 exit:
712         fput(file);
713         return ERR_PTR(err);
714 }
715 EXPORT_SYMBOL(open_exec);
716
717 int kernel_read(struct file *file, loff_t offset,
718                 char *addr, unsigned long count)
719 {
720         mm_segment_t old_fs;
721         loff_t pos = offset;
722         int result;
723
724         old_fs = get_fs();
725         set_fs(get_ds());
726         /* The cast to a user pointer is valid due to the set_fs() */
727         result = vfs_read(file, (void __user *)addr, count, &pos);
728         set_fs(old_fs);
729         return result;
730 }
731
732 EXPORT_SYMBOL(kernel_read);
733
734 static int exec_mmap(struct mm_struct *mm)
735 {
736         struct task_struct *tsk;
737         struct mm_struct * old_mm, *active_mm;
738
739         /* Notify parent that we're no longer interested in the old VM */
740         tsk = current;
741         old_mm = current->mm;
742         sync_mm_rss(tsk, old_mm);
743         mm_release(tsk, old_mm);
744
745         if (old_mm) {
746                 /*
747                  * Make sure that if there is a core dump in progress
748                  * for the old mm, we get out and die instead of going
749                  * through with the exec.  We must hold mmap_sem around
750                  * checking core_state and changing tsk->mm.
751                  */
752                 down_read(&old_mm->mmap_sem);
753                 if (unlikely(old_mm->core_state)) {
754                         up_read(&old_mm->mmap_sem);
755                         return -EINTR;
756                 }
757         }
758         task_lock(tsk);
759         active_mm = tsk->active_mm;
760         tsk->mm = mm;
761         tsk->active_mm = mm;
762         activate_mm(active_mm, mm);
763         if (old_mm && tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
764                 atomic_dec(&old_mm->oom_disable_count);
765                 atomic_inc(&tsk->mm->oom_disable_count);
766         }
767         task_unlock(tsk);
768         arch_pick_mmap_layout(mm);
769         if (old_mm) {
770                 up_read(&old_mm->mmap_sem);
771                 BUG_ON(active_mm != old_mm);
772                 mm_update_next_owner(old_mm);
773                 mmput(old_mm);
774                 return 0;
775         }
776         mmdrop(active_mm);
777         return 0;
778 }
779
780 /*
781  * This function makes sure the current process has its own signal table,
782  * so that flush_signal_handlers can later reset the handlers without
783  * disturbing other processes.  (Other processes might share the signal
784  * table via the CLONE_SIGHAND option to clone().)
785  */
786 static int de_thread(struct task_struct *tsk)
787 {
788         struct signal_struct *sig = tsk->signal;
789         struct sighand_struct *oldsighand = tsk->sighand;
790         spinlock_t *lock = &oldsighand->siglock;
791
792         if (thread_group_empty(tsk))
793                 goto no_thread_group;
794
795         /*
796          * Kill all other threads in the thread group.
797          */
798         spin_lock_irq(lock);
799         if (signal_group_exit(sig)) {
800                 /*
801                  * Another group action in progress, just
802                  * return so that the signal is processed.
803                  */
804                 spin_unlock_irq(lock);
805                 return -EAGAIN;
806         }
807
808         sig->group_exit_task = tsk;
809         sig->notify_count = zap_other_threads(tsk);
810         if (!thread_group_leader(tsk))
811                 sig->notify_count--;
812
813         while (sig->notify_count) {
814                 __set_current_state(TASK_UNINTERRUPTIBLE);
815                 spin_unlock_irq(lock);
816                 schedule();
817                 spin_lock_irq(lock);
818         }
819         spin_unlock_irq(lock);
820
821         /*
822          * At this point all other threads have exited, all we have to
823          * do is to wait for the thread group leader to become inactive,
824          * and to assume its PID:
825          */
826         if (!thread_group_leader(tsk)) {
827                 struct task_struct *leader = tsk->group_leader;
828
829                 sig->notify_count = -1; /* for exit_notify() */
830                 for (;;) {
831                         write_lock_irq(&tasklist_lock);
832                         if (likely(leader->exit_state))
833                                 break;
834                         __set_current_state(TASK_UNINTERRUPTIBLE);
835                         write_unlock_irq(&tasklist_lock);
836                         schedule();
837                 }
838
839                 /*
840                  * The only record we have of the real-time age of a
841                  * process, regardless of execs it's done, is start_time.
842                  * All the past CPU time is accumulated in signal_struct
843                  * from sister threads now dead.  But in this non-leader
844                  * exec, nothing survives from the original leader thread,
845                  * whose birth marks the true age of this process now.
846                  * When we take on its identity by switching to its PID, we
847                  * also take its birthdate (always earlier than our own).
848                  */
849                 tsk->start_time = leader->start_time;
850
851                 BUG_ON(!same_thread_group(leader, tsk));
852                 BUG_ON(has_group_leader_pid(tsk));
853                 /*
854                  * An exec() starts a new thread group with the
855                  * TGID of the previous thread group. Rehash the
856                  * two threads with a switched PID, and release
857                  * the former thread group leader:
858                  */
859
860                 /* Become a process group leader with the old leader's pid.
861                  * The old leader becomes a thread of the this thread group.
862                  * Note: The old leader also uses this pid until release_task
863                  *       is called.  Odd but simple and correct.
864                  */
865                 detach_pid(tsk, PIDTYPE_PID);
866                 tsk->pid = leader->pid;
867                 attach_pid(tsk, PIDTYPE_PID,  task_pid(leader));
868                 transfer_pid(leader, tsk, PIDTYPE_PGID);
869                 transfer_pid(leader, tsk, PIDTYPE_SID);
870
871                 list_replace_rcu(&leader->tasks, &tsk->tasks);
872                 list_replace_init(&leader->sibling, &tsk->sibling);
873
874                 tsk->group_leader = tsk;
875                 leader->group_leader = tsk;
876
877                 tsk->exit_signal = SIGCHLD;
878
879                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
880                 leader->exit_state = EXIT_DEAD;
881                 write_unlock_irq(&tasklist_lock);
882
883                 release_task(leader);
884         }
885
886         sig->group_exit_task = NULL;
887         sig->notify_count = 0;
888
889 no_thread_group:
890         if (current->mm)
891                 setmax_mm_hiwater_rss(&sig->maxrss, current->mm);
892
893         exit_itimers(sig);
894         flush_itimer_signals();
895
896         if (atomic_read(&oldsighand->count) != 1) {
897                 struct sighand_struct *newsighand;
898                 /*
899                  * This ->sighand is shared with the CLONE_SIGHAND
900                  * but not CLONE_THREAD task, switch to the new one.
901                  */
902                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
903                 if (!newsighand)
904                         return -ENOMEM;
905
906                 atomic_set(&newsighand->count, 1);
907                 memcpy(newsighand->action, oldsighand->action,
908                        sizeof(newsighand->action));
909
910                 write_lock_irq(&tasklist_lock);
911                 spin_lock(&oldsighand->siglock);
912                 rcu_assign_pointer(tsk->sighand, newsighand);
913                 spin_unlock(&oldsighand->siglock);
914                 write_unlock_irq(&tasklist_lock);
915
916                 __cleanup_sighand(oldsighand);
917         }
918
919         BUG_ON(!thread_group_leader(tsk));
920         return 0;
921 }
922
923 /*
924  * These functions flushes out all traces of the currently running executable
925  * so that a new one can be started
926  */
927 static void flush_old_files(struct files_struct * files)
928 {
929         long j = -1;
930         struct fdtable *fdt;
931
932         spin_lock(&files->file_lock);
933         for (;;) {
934                 unsigned long set, i;
935
936                 j++;
937                 i = j * __NFDBITS;
938                 fdt = files_fdtable(files);
939                 if (i >= fdt->max_fds)
940                         break;
941                 set = fdt->close_on_exec->fds_bits[j];
942                 if (!set)
943                         continue;
944                 fdt->close_on_exec->fds_bits[j] = 0;
945                 spin_unlock(&files->file_lock);
946                 for ( ; set ; i++,set >>= 1) {
947                         if (set & 1) {
948                                 sys_close(i);
949                         }
950                 }
951                 spin_lock(&files->file_lock);
952
953         }
954         spin_unlock(&files->file_lock);
955 }
956
957 char *get_task_comm(char *buf, struct task_struct *tsk)
958 {
959         /* buf must be at least sizeof(tsk->comm) in size */
960         task_lock(tsk);
961         strncpy(buf, tsk->comm, sizeof(tsk->comm));
962         task_unlock(tsk);
963         return buf;
964 }
965
966 void set_task_comm(struct task_struct *tsk, char *buf)
967 {
968         task_lock(tsk);
969
970         /*
971          * Threads may access current->comm without holding
972          * the task lock, so write the string carefully.
973          * Readers without a lock may see incomplete new
974          * names but are safe from non-terminating string reads.
975          */
976         memset(tsk->comm, 0, TASK_COMM_LEN);
977         wmb();
978         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
979         task_unlock(tsk);
980         perf_event_comm(tsk);
981 }
982
983 int flush_old_exec(struct linux_binprm * bprm)
984 {
985         int retval;
986
987         /*
988          * Make sure we have a private signal table and that
989          * we are unassociated from the previous thread group.
990          */
991         retval = de_thread(current);
992         if (retval)
993                 goto out;
994
995         set_mm_exe_file(bprm->mm, bprm->file);
996
997         /*
998          * Release all of the old mmap stuff
999          */
1000         retval = exec_mmap(bprm->mm);
1001         if (retval)
1002                 goto out;
1003
1004         bprm->mm = NULL;                /* We're using it now */
1005
1006         current->flags &= ~PF_RANDOMIZE;
1007         flush_thread();
1008         current->personality &= ~bprm->per_clear;
1009
1010         return 0;
1011
1012 out:
1013         return retval;
1014 }
1015 EXPORT_SYMBOL(flush_old_exec);
1016
1017 void setup_new_exec(struct linux_binprm * bprm)
1018 {
1019         int i, ch;
1020         const char *name;
1021         char tcomm[sizeof(current->comm)];
1022
1023         arch_pick_mmap_layout(current->mm);
1024
1025         /* This is the point of no return */
1026         current->sas_ss_sp = current->sas_ss_size = 0;
1027
1028         if (current_euid() == current_uid() && current_egid() == current_gid())
1029                 set_dumpable(current->mm, 1);
1030         else
1031                 set_dumpable(current->mm, suid_dumpable);
1032
1033         name = bprm->filename;
1034
1035         /* Copies the binary name from after last slash */
1036         for (i=0; (ch = *(name++)) != '\0';) {
1037                 if (ch == '/')
1038                         i = 0; /* overwrite what we wrote */
1039                 else
1040                         if (i < (sizeof(tcomm) - 1))
1041                                 tcomm[i++] = ch;
1042         }
1043         tcomm[i] = '\0';
1044         set_task_comm(current, tcomm);
1045
1046         /* Set the new mm task size. We have to do that late because it may
1047          * depend on TIF_32BIT which is only updated in flush_thread() on
1048          * some architectures like powerpc
1049          */
1050         current->mm->task_size = TASK_SIZE;
1051
1052         /* install the new credentials */
1053         if (bprm->cred->uid != current_euid() ||
1054             bprm->cred->gid != current_egid()) {
1055                 current->pdeath_signal = 0;
1056         } else if (file_permission(bprm->file, MAY_READ) ||
1057                    bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) {
1058                 set_dumpable(current->mm, suid_dumpable);
1059         }
1060
1061         /*
1062          * Flush performance counters when crossing a
1063          * security domain:
1064          */
1065         if (!get_dumpable(current->mm))
1066                 perf_event_exit_task(current);
1067
1068         /* An exec changes our domain. We are no longer part of the thread
1069            group */
1070
1071         current->self_exec_id++;
1072                         
1073         flush_signal_handlers(current, 0);
1074         flush_old_files(current->files);
1075 }
1076 EXPORT_SYMBOL(setup_new_exec);
1077
1078 /*
1079  * Prepare credentials and lock ->cred_guard_mutex.
1080  * install_exec_creds() commits the new creds and drops the lock.
1081  * Or, if exec fails before, free_bprm() should release ->cred and
1082  * and unlock.
1083  */
1084 int prepare_bprm_creds(struct linux_binprm *bprm)
1085 {
1086         if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1087                 return -ERESTARTNOINTR;
1088
1089         bprm->cred = prepare_exec_creds();
1090         if (likely(bprm->cred))
1091                 return 0;
1092
1093         mutex_unlock(&current->signal->cred_guard_mutex);
1094         return -ENOMEM;
1095 }
1096
1097 void free_bprm(struct linux_binprm *bprm)
1098 {
1099         free_arg_pages(bprm);
1100         if (bprm->cred) {
1101                 mutex_unlock(&current->signal->cred_guard_mutex);
1102                 abort_creds(bprm->cred);
1103         }
1104         kfree(bprm);
1105 }
1106
1107 /*
1108  * install the new credentials for this executable
1109  */
1110 void install_exec_creds(struct linux_binprm *bprm)
1111 {
1112         security_bprm_committing_creds(bprm);
1113
1114         commit_creds(bprm->cred);
1115         bprm->cred = NULL;
1116         /*
1117          * cred_guard_mutex must be held at least to this point to prevent
1118          * ptrace_attach() from altering our determination of the task's
1119          * credentials; any time after this it may be unlocked.
1120          */
1121         security_bprm_committed_creds(bprm);
1122         mutex_unlock(&current->signal->cred_guard_mutex);
1123 }
1124 EXPORT_SYMBOL(install_exec_creds);
1125
1126 /*
1127  * determine how safe it is to execute the proposed program
1128  * - the caller must hold ->cred_guard_mutex to protect against
1129  *   PTRACE_ATTACH
1130  */
1131 int check_unsafe_exec(struct linux_binprm *bprm)
1132 {
1133         struct task_struct *p = current, *t;
1134         unsigned n_fs;
1135         int res = 0;
1136
1137         bprm->unsafe = tracehook_unsafe_exec(p);
1138
1139         n_fs = 1;
1140         spin_lock(&p->fs->lock);
1141         rcu_read_lock();
1142         for (t = next_thread(p); t != p; t = next_thread(t)) {
1143                 if (t->fs == p->fs)
1144                         n_fs++;
1145         }
1146         rcu_read_unlock();
1147
1148         if (p->fs->users > n_fs) {
1149                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1150         } else {
1151                 res = -EAGAIN;
1152                 if (!p->fs->in_exec) {
1153                         p->fs->in_exec = 1;
1154                         res = 1;
1155                 }
1156         }
1157         spin_unlock(&p->fs->lock);
1158
1159         return res;
1160 }
1161
1162 /* 
1163  * Fill the binprm structure from the inode. 
1164  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1165  *
1166  * This may be called multiple times for binary chains (scripts for example).
1167  */
1168 int prepare_binprm(struct linux_binprm *bprm)
1169 {
1170         umode_t mode;
1171         struct inode * inode = bprm->file->f_path.dentry->d_inode;
1172         int retval;
1173
1174         mode = inode->i_mode;
1175         if (bprm->file->f_op == NULL)
1176                 return -EACCES;
1177
1178         /* clear any previous set[ug]id data from a previous binary */
1179         bprm->cred->euid = current_euid();
1180         bprm->cred->egid = current_egid();
1181
1182         if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
1183                 /* Set-uid? */
1184                 if (mode & S_ISUID) {
1185                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1186                         bprm->cred->euid = inode->i_uid;
1187                 }
1188
1189                 /* Set-gid? */
1190                 /*
1191                  * If setgid is set but no group execute bit then this
1192                  * is a candidate for mandatory locking, not a setgid
1193                  * executable.
1194                  */
1195                 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1196                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1197                         bprm->cred->egid = inode->i_gid;
1198                 }
1199         }
1200
1201         /* fill in binprm security blob */
1202         retval = security_bprm_set_creds(bprm);
1203         if (retval)
1204                 return retval;
1205         bprm->cred_prepared = 1;
1206
1207         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1208         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1209 }
1210
1211 EXPORT_SYMBOL(prepare_binprm);
1212
1213 /*
1214  * Arguments are '\0' separated strings found at the location bprm->p
1215  * points to; chop off the first by relocating brpm->p to right after
1216  * the first '\0' encountered.
1217  */
1218 int remove_arg_zero(struct linux_binprm *bprm)
1219 {
1220         int ret = 0;
1221         unsigned long offset;
1222         char *kaddr;
1223         struct page *page;
1224
1225         if (!bprm->argc)
1226                 return 0;
1227
1228         do {
1229                 offset = bprm->p & ~PAGE_MASK;
1230                 page = get_arg_page(bprm, bprm->p, 0);
1231                 if (!page) {
1232                         ret = -EFAULT;
1233                         goto out;
1234                 }
1235                 kaddr = kmap_atomic(page, KM_USER0);
1236
1237                 for (; offset < PAGE_SIZE && kaddr[offset];
1238                                 offset++, bprm->p++)
1239                         ;
1240
1241                 kunmap_atomic(kaddr, KM_USER0);
1242                 put_arg_page(page);
1243
1244                 if (offset == PAGE_SIZE)
1245                         free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1246         } while (offset == PAGE_SIZE);
1247
1248         bprm->p++;
1249         bprm->argc--;
1250         ret = 0;
1251
1252 out:
1253         return ret;
1254 }
1255 EXPORT_SYMBOL(remove_arg_zero);
1256
1257 /*
1258  * cycle the list of binary formats handler, until one recognizes the image
1259  */
1260 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1261 {
1262         unsigned int depth = bprm->recursion_depth;
1263         int try,retval;
1264         struct linux_binfmt *fmt;
1265
1266         retval = security_bprm_check(bprm);
1267         if (retval)
1268                 return retval;
1269
1270         /* kernel module loader fixup */
1271         /* so we don't try to load run modprobe in kernel space. */
1272         set_fs(USER_DS);
1273
1274         retval = audit_bprm(bprm);
1275         if (retval)
1276                 return retval;
1277
1278         retval = -ENOENT;
1279         for (try=0; try<2; try++) {
1280                 read_lock(&binfmt_lock);
1281                 list_for_each_entry(fmt, &formats, lh) {
1282                         int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1283                         if (!fn)
1284                                 continue;
1285                         if (!try_module_get(fmt->module))
1286                                 continue;
1287                         read_unlock(&binfmt_lock);
1288                         retval = fn(bprm, regs);
1289                         /*
1290                          * Restore the depth counter to its starting value
1291                          * in this call, so we don't have to rely on every
1292                          * load_binary function to restore it on return.
1293                          */
1294                         bprm->recursion_depth = depth;
1295                         if (retval >= 0) {
1296                                 if (depth == 0)
1297                                         tracehook_report_exec(fmt, bprm, regs);
1298                                 put_binfmt(fmt);
1299                                 allow_write_access(bprm->file);
1300                                 if (bprm->file)
1301                                         fput(bprm->file);
1302                                 bprm->file = NULL;
1303                                 current->did_exec = 1;
1304                                 proc_exec_connector(current);
1305                                 return retval;
1306                         }
1307                         read_lock(&binfmt_lock);
1308                         put_binfmt(fmt);
1309                         if (retval != -ENOEXEC || bprm->mm == NULL)
1310                                 break;
1311                         if (!bprm->file) {
1312                                 read_unlock(&binfmt_lock);
1313                                 return retval;
1314                         }
1315                 }
1316                 read_unlock(&binfmt_lock);
1317                 if (retval != -ENOEXEC || bprm->mm == NULL) {
1318                         break;
1319 #ifdef CONFIG_MODULES
1320                 } else {
1321 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1322                         if (printable(bprm->buf[0]) &&
1323                             printable(bprm->buf[1]) &&
1324                             printable(bprm->buf[2]) &&
1325                             printable(bprm->buf[3]))
1326                                 break; /* -ENOEXEC */
1327                         request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1328 #endif
1329                 }
1330         }
1331         return retval;
1332 }
1333
1334 EXPORT_SYMBOL(search_binary_handler);
1335
1336 /*
1337  * sys_execve() executes a new program.
1338  */
1339 int do_execve(const char * filename,
1340         const char __user *const __user *argv,
1341         const char __user *const __user *envp,
1342         struct pt_regs * regs)
1343 {
1344         struct linux_binprm *bprm;
1345         struct file *file;
1346         struct files_struct *displaced;
1347         bool clear_in_exec;
1348         int retval;
1349
1350         retval = unshare_files(&displaced);
1351         if (retval)
1352                 goto out_ret;
1353
1354         retval = -ENOMEM;
1355         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1356         if (!bprm)
1357                 goto out_files;
1358
1359         retval = prepare_bprm_creds(bprm);
1360         if (retval)
1361                 goto out_free;
1362
1363         retval = check_unsafe_exec(bprm);
1364         if (retval < 0)
1365                 goto out_free;
1366         clear_in_exec = retval;
1367         current->in_execve = 1;
1368
1369         file = open_exec(filename);
1370         retval = PTR_ERR(file);
1371         if (IS_ERR(file))
1372                 goto out_unmark;
1373
1374         sched_exec();
1375
1376         bprm->file = file;
1377         bprm->filename = filename;
1378         bprm->interp = filename;
1379
1380         retval = bprm_mm_init(bprm);
1381         if (retval)
1382                 goto out_file;
1383
1384         bprm->argc = count(argv, MAX_ARG_STRINGS);
1385         if ((retval = bprm->argc) < 0)
1386                 goto out;
1387
1388         bprm->envc = count(envp, MAX_ARG_STRINGS);
1389         if ((retval = bprm->envc) < 0)
1390                 goto out;
1391
1392         retval = prepare_binprm(bprm);
1393         if (retval < 0)
1394                 goto out;
1395
1396         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1397         if (retval < 0)
1398                 goto out;
1399
1400         bprm->exec = bprm->p;
1401         retval = copy_strings(bprm->envc, envp, bprm);
1402         if (retval < 0)
1403                 goto out;
1404
1405         retval = copy_strings(bprm->argc, argv, bprm);
1406         if (retval < 0)
1407                 goto out;
1408
1409         current->flags &= ~PF_KTHREAD;
1410         retval = search_binary_handler(bprm,regs);
1411         if (retval < 0)
1412                 goto out;
1413
1414         /* execve succeeded */
1415         current->fs->in_exec = 0;
1416         current->in_execve = 0;
1417         acct_update_integrals(current);
1418         free_bprm(bprm);
1419         if (displaced)
1420                 put_files_struct(displaced);
1421         return retval;
1422
1423 out:
1424         if (bprm->mm)
1425                 mmput (bprm->mm);
1426
1427 out_file:
1428         if (bprm->file) {
1429                 allow_write_access(bprm->file);
1430                 fput(bprm->file);
1431         }
1432
1433 out_unmark:
1434         if (clear_in_exec)
1435                 current->fs->in_exec = 0;
1436         current->in_execve = 0;
1437
1438 out_free:
1439         free_bprm(bprm);
1440
1441 out_files:
1442         if (displaced)
1443                 reset_files_struct(displaced);
1444 out_ret:
1445         return retval;
1446 }
1447
1448 void set_binfmt(struct linux_binfmt *new)
1449 {
1450         struct mm_struct *mm = current->mm;
1451
1452         if (mm->binfmt)
1453                 module_put(mm->binfmt->module);
1454
1455         mm->binfmt = new;
1456         if (new)
1457                 __module_get(new->module);
1458 }
1459
1460 EXPORT_SYMBOL(set_binfmt);
1461
1462 /* format_corename will inspect the pattern parameter, and output a
1463  * name into corename, which must have space for at least
1464  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
1465  */
1466 static int format_corename(char *corename, long signr)
1467 {
1468         const struct cred *cred = current_cred();
1469         const char *pat_ptr = core_pattern;
1470         int ispipe = (*pat_ptr == '|');
1471         char *out_ptr = corename;
1472         char *const out_end = corename + CORENAME_MAX_SIZE;
1473         int rc;
1474         int pid_in_pattern = 0;
1475
1476         /* Repeat as long as we have more pattern to process and more output
1477            space */
1478         while (*pat_ptr) {
1479                 if (*pat_ptr != '%') {
1480                         if (out_ptr == out_end)
1481                                 goto out;
1482                         *out_ptr++ = *pat_ptr++;
1483                 } else {
1484                         switch (*++pat_ptr) {
1485                         case 0:
1486                                 goto out;
1487                         /* Double percent, output one percent */
1488                         case '%':
1489                                 if (out_ptr == out_end)
1490                                         goto out;
1491                                 *out_ptr++ = '%';
1492                                 break;
1493                         /* pid */
1494                         case 'p':
1495                                 pid_in_pattern = 1;
1496                                 rc = snprintf(out_ptr, out_end - out_ptr,
1497                                               "%d", task_tgid_vnr(current));
1498                                 if (rc > out_end - out_ptr)
1499                                         goto out;
1500                                 out_ptr += rc;
1501                                 break;
1502                         /* uid */
1503                         case 'u':
1504                                 rc = snprintf(out_ptr, out_end - out_ptr,
1505                                               "%d", cred->uid);
1506                                 if (rc > out_end - out_ptr)
1507                                         goto out;
1508                                 out_ptr += rc;
1509                                 break;
1510                         /* gid */
1511                         case 'g':
1512                                 rc = snprintf(out_ptr, out_end - out_ptr,
1513                                               "%d", cred->gid);
1514                                 if (rc > out_end - out_ptr)
1515                                         goto out;
1516                                 out_ptr += rc;
1517                                 break;
1518                         /* signal that caused the coredump */
1519                         case 's':
1520                                 rc = snprintf(out_ptr, out_end - out_ptr,
1521                                               "%ld", signr);
1522                                 if (rc > out_end - out_ptr)
1523                                         goto out;
1524                                 out_ptr += rc;
1525                                 break;
1526                         /* UNIX time of coredump */
1527                         case 't': {
1528                                 struct timeval tv;
1529                                 do_gettimeofday(&tv);
1530                                 rc = snprintf(out_ptr, out_end - out_ptr,
1531                                               "%lu", tv.tv_sec);
1532                                 if (rc > out_end - out_ptr)
1533                                         goto out;
1534                                 out_ptr += rc;
1535                                 break;
1536                         }
1537                         /* hostname */
1538                         case 'h':
1539                                 down_read(&uts_sem);
1540                                 rc = snprintf(out_ptr, out_end - out_ptr,
1541                                               "%s", utsname()->nodename);
1542                                 up_read(&uts_sem);
1543                                 if (rc > out_end - out_ptr)
1544                                         goto out;
1545                                 out_ptr += rc;
1546                                 break;
1547                         /* executable */
1548                         case 'e':
1549                                 rc = snprintf(out_ptr, out_end - out_ptr,
1550                                               "%s", current->comm);
1551                                 if (rc > out_end - out_ptr)
1552                                         goto out;
1553                                 out_ptr += rc;
1554                                 break;
1555                         /* core limit size */
1556                         case 'c':
1557                                 rc = snprintf(out_ptr, out_end - out_ptr,
1558                                               "%lu", rlimit(RLIMIT_CORE));
1559                                 if (rc > out_end - out_ptr)
1560                                         goto out;
1561                                 out_ptr += rc;
1562                                 break;
1563                         default:
1564                                 break;
1565                         }
1566                         ++pat_ptr;
1567                 }
1568         }
1569         /* Backward compatibility with core_uses_pid:
1570          *
1571          * If core_pattern does not include a %p (as is the default)
1572          * and core_uses_pid is set, then .%pid will be appended to
1573          * the filename. Do not do this for piped commands. */
1574         if (!ispipe && !pid_in_pattern && core_uses_pid) {
1575                 rc = snprintf(out_ptr, out_end - out_ptr,
1576                               ".%d", task_tgid_vnr(current));
1577                 if (rc > out_end - out_ptr)
1578                         goto out;
1579                 out_ptr += rc;
1580         }
1581 out:
1582         *out_ptr = 0;
1583         return ispipe;
1584 }
1585
1586 static int zap_process(struct task_struct *start, int exit_code)
1587 {
1588         struct task_struct *t;
1589         int nr = 0;
1590
1591         start->signal->flags = SIGNAL_GROUP_EXIT;
1592         start->signal->group_exit_code = exit_code;
1593         start->signal->group_stop_count = 0;
1594
1595         t = start;
1596         do {
1597                 if (t != current && t->mm) {
1598                         sigaddset(&t->pending.signal, SIGKILL);
1599                         signal_wake_up(t, 1);
1600                         nr++;
1601                 }
1602         } while_each_thread(start, t);
1603
1604         return nr;
1605 }
1606
1607 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
1608                                 struct core_state *core_state, int exit_code)
1609 {
1610         struct task_struct *g, *p;
1611         unsigned long flags;
1612         int nr = -EAGAIN;
1613
1614         spin_lock_irq(&tsk->sighand->siglock);
1615         if (!signal_group_exit(tsk->signal)) {
1616                 mm->core_state = core_state;
1617                 nr = zap_process(tsk, exit_code);
1618         }
1619         spin_unlock_irq(&tsk->sighand->siglock);
1620         if (unlikely(nr < 0))
1621                 return nr;
1622
1623         if (atomic_read(&mm->mm_users) == nr + 1)
1624                 goto done;
1625         /*
1626          * We should find and kill all tasks which use this mm, and we should
1627          * count them correctly into ->nr_threads. We don't take tasklist
1628          * lock, but this is safe wrt:
1629          *
1630          * fork:
1631          *      None of sub-threads can fork after zap_process(leader). All
1632          *      processes which were created before this point should be
1633          *      visible to zap_threads() because copy_process() adds the new
1634          *      process to the tail of init_task.tasks list, and lock/unlock
1635          *      of ->siglock provides a memory barrier.
1636          *
1637          * do_exit:
1638          *      The caller holds mm->mmap_sem. This means that the task which
1639          *      uses this mm can't pass exit_mm(), so it can't exit or clear
1640          *      its ->mm.
1641          *
1642          * de_thread:
1643          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
1644          *      we must see either old or new leader, this does not matter.
1645          *      However, it can change p->sighand, so lock_task_sighand(p)
1646          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
1647          *      it can't fail.
1648          *
1649          *      Note also that "g" can be the old leader with ->mm == NULL
1650          *      and already unhashed and thus removed from ->thread_group.
1651          *      This is OK, __unhash_process()->list_del_rcu() does not
1652          *      clear the ->next pointer, we will find the new leader via
1653          *      next_thread().
1654          */
1655         rcu_read_lock();
1656         for_each_process(g) {
1657                 if (g == tsk->group_leader)
1658                         continue;
1659                 if (g->flags & PF_KTHREAD)
1660                         continue;
1661                 p = g;
1662                 do {
1663                         if (p->mm) {
1664                                 if (unlikely(p->mm == mm)) {
1665                                         lock_task_sighand(p, &flags);
1666                                         nr += zap_process(p, exit_code);
1667                                         unlock_task_sighand(p, &flags);
1668                                 }
1669                                 break;
1670                         }
1671                 } while_each_thread(g, p);
1672         }
1673         rcu_read_unlock();
1674 done:
1675         atomic_set(&core_state->nr_threads, nr);
1676         return nr;
1677 }
1678
1679 static int coredump_wait(int exit_code, struct core_state *core_state)
1680 {
1681         struct task_struct *tsk = current;
1682         struct mm_struct *mm = tsk->mm;
1683         struct completion *vfork_done;
1684         int core_waiters = -EBUSY;
1685
1686         init_completion(&core_state->startup);
1687         core_state->dumper.task = tsk;
1688         core_state->dumper.next = NULL;
1689
1690         down_write(&mm->mmap_sem);
1691         if (!mm->core_state)
1692                 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
1693         up_write(&mm->mmap_sem);
1694
1695         if (unlikely(core_waiters < 0))
1696                 goto fail;
1697
1698         /*
1699          * Make sure nobody is waiting for us to release the VM,
1700          * otherwise we can deadlock when we wait on each other
1701          */
1702         vfork_done = tsk->vfork_done;
1703         if (vfork_done) {
1704                 tsk->vfork_done = NULL;
1705                 complete(vfork_done);
1706         }
1707
1708         if (core_waiters)
1709                 wait_for_completion(&core_state->startup);
1710 fail:
1711         return core_waiters;
1712 }
1713
1714 static void coredump_finish(struct mm_struct *mm)
1715 {
1716         struct core_thread *curr, *next;
1717         struct task_struct *task;
1718
1719         next = mm->core_state->dumper.next;
1720         while ((curr = next) != NULL) {
1721                 next = curr->next;
1722                 task = curr->task;
1723                 /*
1724                  * see exit_mm(), curr->task must not see
1725                  * ->task == NULL before we read ->next.
1726                  */
1727                 smp_mb();
1728                 curr->task = NULL;
1729                 wake_up_process(task);
1730         }
1731
1732         mm->core_state = NULL;
1733 }
1734
1735 /*
1736  * set_dumpable converts traditional three-value dumpable to two flags and
1737  * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
1738  * these bits are not changed atomically.  So get_dumpable can observe the
1739  * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
1740  * return either old dumpable or new one by paying attention to the order of
1741  * modifying the bits.
1742  *
1743  * dumpable |   mm->flags (binary)
1744  * old  new | initial interim  final
1745  * ---------+-----------------------
1746  *  0    1  |   00      01      01
1747  *  0    2  |   00      10(*)   11
1748  *  1    0  |   01      00      00
1749  *  1    2  |   01      11      11
1750  *  2    0  |   11      10(*)   00
1751  *  2    1  |   11      11      01
1752  *
1753  * (*) get_dumpable regards interim value of 10 as 11.
1754  */
1755 void set_dumpable(struct mm_struct *mm, int value)
1756 {
1757         switch (value) {
1758         case 0:
1759                 clear_bit(MMF_DUMPABLE, &mm->flags);
1760                 smp_wmb();
1761                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1762                 break;
1763         case 1:
1764                 set_bit(MMF_DUMPABLE, &mm->flags);
1765                 smp_wmb();
1766                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1767                 break;
1768         case 2:
1769                 set_bit(MMF_DUMP_SECURELY, &mm->flags);
1770                 smp_wmb();
1771                 set_bit(MMF_DUMPABLE, &mm->flags);
1772                 break;
1773         }
1774 }
1775
1776 static int __get_dumpable(unsigned long mm_flags)
1777 {
1778         int ret;
1779
1780         ret = mm_flags & MMF_DUMPABLE_MASK;
1781         return (ret >= 2) ? 2 : ret;
1782 }
1783
1784 int get_dumpable(struct mm_struct *mm)
1785 {
1786         return __get_dumpable(mm->flags);
1787 }
1788
1789 static void wait_for_dump_helpers(struct file *file)
1790 {
1791         struct pipe_inode_info *pipe;
1792
1793         pipe = file->f_path.dentry->d_inode->i_pipe;
1794
1795         pipe_lock(pipe);
1796         pipe->readers++;
1797         pipe->writers--;
1798
1799         while ((pipe->readers > 1) && (!signal_pending(current))) {
1800                 wake_up_interruptible_sync(&pipe->wait);
1801                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
1802                 pipe_wait(pipe);
1803         }
1804
1805         pipe->readers--;
1806         pipe->writers++;
1807         pipe_unlock(pipe);
1808
1809 }
1810
1811
1812 /*
1813  * uhm_pipe_setup
1814  * helper function to customize the process used
1815  * to collect the core in userspace.  Specifically
1816  * it sets up a pipe and installs it as fd 0 (stdin)
1817  * for the process.  Returns 0 on success, or
1818  * PTR_ERR on failure.
1819  * Note that it also sets the core limit to 1.  This
1820  * is a special value that we use to trap recursive
1821  * core dumps
1822  */
1823 static int umh_pipe_setup(struct subprocess_info *info)
1824 {
1825         struct file *rp, *wp;
1826         struct fdtable *fdt;
1827         struct coredump_params *cp = (struct coredump_params *)info->data;
1828         struct files_struct *cf = current->files;
1829
1830         wp = create_write_pipe(0);
1831         if (IS_ERR(wp))
1832                 return PTR_ERR(wp);
1833
1834         rp = create_read_pipe(wp, 0);
1835         if (IS_ERR(rp)) {
1836                 free_write_pipe(wp);
1837                 return PTR_ERR(rp);
1838         }
1839
1840         cp->file = wp;
1841
1842         sys_close(0);
1843         fd_install(0, rp);
1844         spin_lock(&cf->file_lock);
1845         fdt = files_fdtable(cf);
1846         FD_SET(0, fdt->open_fds);
1847         FD_CLR(0, fdt->close_on_exec);
1848         spin_unlock(&cf->file_lock);
1849
1850         /* and disallow core files too */
1851         current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
1852
1853         return 0;
1854 }
1855
1856 void do_coredump(long signr, int exit_code, struct pt_regs *regs)
1857 {
1858         struct core_state core_state;
1859         char corename[CORENAME_MAX_SIZE + 1];
1860         struct mm_struct *mm = current->mm;
1861         struct linux_binfmt * binfmt;
1862         const struct cred *old_cred;
1863         struct cred *cred;
1864         int retval = 0;
1865         int flag = 0;
1866         int ispipe;
1867         static atomic_t core_dump_count = ATOMIC_INIT(0);
1868         struct coredump_params cprm = {
1869                 .signr = signr,
1870                 .regs = regs,
1871                 .limit = rlimit(RLIMIT_CORE),
1872                 /*
1873                  * We must use the same mm->flags while dumping core to avoid
1874                  * inconsistency of bit flags, since this flag is not protected
1875                  * by any locks.
1876                  */
1877                 .mm_flags = mm->flags,
1878         };
1879
1880         audit_core_dumps(signr);
1881
1882         binfmt = mm->binfmt;
1883         if (!binfmt || !binfmt->core_dump)
1884                 goto fail;
1885         if (!__get_dumpable(cprm.mm_flags))
1886                 goto fail;
1887
1888         cred = prepare_creds();
1889         if (!cred)
1890                 goto fail;
1891         /*
1892          *      We cannot trust fsuid as being the "true" uid of the
1893          *      process nor do we know its entire history. We only know it
1894          *      was tainted so we dump it as root in mode 2.
1895          */
1896         if (__get_dumpable(cprm.mm_flags) == 2) {
1897                 /* Setuid core dump mode */
1898                 flag = O_EXCL;          /* Stop rewrite attacks */
1899                 cred->fsuid = 0;        /* Dump root private */
1900         }
1901
1902         retval = coredump_wait(exit_code, &core_state);
1903         if (retval < 0)
1904                 goto fail_creds;
1905
1906         old_cred = override_creds(cred);
1907
1908         /*
1909          * Clear any false indication of pending signals that might
1910          * be seen by the filesystem code called to write the core file.
1911          */
1912         clear_thread_flag(TIF_SIGPENDING);
1913
1914         ispipe = format_corename(corename, signr);
1915
1916         if (ispipe) {
1917                 int dump_count;
1918                 char **helper_argv;
1919
1920                 if (cprm.limit == 1) {
1921                         /*
1922                          * Normally core limits are irrelevant to pipes, since
1923                          * we're not writing to the file system, but we use
1924                          * cprm.limit of 1 here as a speacial value. Any
1925                          * non-1 limit gets set to RLIM_INFINITY below, but
1926                          * a limit of 0 skips the dump.  This is a consistent
1927                          * way to catch recursive crashes.  We can still crash
1928                          * if the core_pattern binary sets RLIM_CORE =  !1
1929                          * but it runs as root, and can do lots of stupid things
1930                          * Note that we use task_tgid_vnr here to grab the pid
1931                          * of the process group leader.  That way we get the
1932                          * right pid if a thread in a multi-threaded
1933                          * core_pattern process dies.
1934                          */
1935                         printk(KERN_WARNING
1936                                 "Process %d(%s) has RLIMIT_CORE set to 1\n",
1937                                 task_tgid_vnr(current), current->comm);
1938                         printk(KERN_WARNING "Aborting core\n");
1939                         goto fail_unlock;
1940                 }
1941                 cprm.limit = RLIM_INFINITY;
1942
1943                 dump_count = atomic_inc_return(&core_dump_count);
1944                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
1945                         printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
1946                                task_tgid_vnr(current), current->comm);
1947                         printk(KERN_WARNING "Skipping core dump\n");
1948                         goto fail_dropcount;
1949                 }
1950
1951                 helper_argv = argv_split(GFP_KERNEL, corename+1, NULL);
1952                 if (!helper_argv) {
1953                         printk(KERN_WARNING "%s failed to allocate memory\n",
1954                                __func__);
1955                         goto fail_dropcount;
1956                 }
1957
1958                 retval = call_usermodehelper_fns(helper_argv[0], helper_argv,
1959                                         NULL, UMH_WAIT_EXEC, umh_pipe_setup,
1960                                         NULL, &cprm);
1961                 argv_free(helper_argv);
1962                 if (retval) {
1963                         printk(KERN_INFO "Core dump to %s pipe failed\n",
1964                                corename);
1965                         goto close_fail;
1966                 }
1967         } else {
1968                 struct inode *inode;
1969
1970                 if (cprm.limit < binfmt->min_coredump)
1971                         goto fail_unlock;
1972
1973                 cprm.file = filp_open(corename,
1974                                  O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
1975                                  0600);
1976                 if (IS_ERR(cprm.file))
1977                         goto fail_unlock;
1978
1979                 inode = cprm.file->f_path.dentry->d_inode;
1980                 if (inode->i_nlink > 1)
1981                         goto close_fail;
1982                 if (d_unhashed(cprm.file->f_path.dentry))
1983                         goto close_fail;
1984                 /*
1985                  * AK: actually i see no reason to not allow this for named
1986                  * pipes etc, but keep the previous behaviour for now.
1987                  */
1988                 if (!S_ISREG(inode->i_mode))
1989                         goto close_fail;
1990                 /*
1991                  * Dont allow local users get cute and trick others to coredump
1992                  * into their pre-created files.
1993                  */
1994                 if (inode->i_uid != current_fsuid())
1995                         goto close_fail;
1996                 if (!cprm.file->f_op || !cprm.file->f_op->write)
1997                         goto close_fail;
1998                 if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
1999                         goto close_fail;
2000         }
2001
2002         retval = binfmt->core_dump(&cprm);
2003         if (retval)
2004                 current->signal->group_exit_code |= 0x80;
2005
2006         if (ispipe && core_pipe_limit)
2007                 wait_for_dump_helpers(cprm.file);
2008 close_fail:
2009         if (cprm.file)
2010                 filp_close(cprm.file, NULL);
2011 fail_dropcount:
2012         if (ispipe)
2013                 atomic_dec(&core_dump_count);
2014 fail_unlock:
2015         coredump_finish(mm);
2016         revert_creds(old_cred);
2017 fail_creds:
2018         put_cred(cred);
2019 fail:
2020         return;
2021 }
2022
2023 /*
2024  * Core dumping helper functions.  These are the only things you should
2025  * do on a core-file: use only these functions to write out all the
2026  * necessary info.
2027  */
2028 int dump_write(struct file *file, const void *addr, int nr)
2029 {
2030         return access_ok(VERIFY_READ, addr, nr) && file->f_op->write(file, addr, nr, &file->f_pos) == nr;
2031 }
2032 EXPORT_SYMBOL(dump_write);
2033
2034 int dump_seek(struct file *file, loff_t off)
2035 {
2036         int ret = 1;
2037
2038         if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
2039                 if (file->f_op->llseek(file, off, SEEK_CUR) < 0)
2040                         return 0;
2041         } else {
2042                 char *buf = (char *)get_zeroed_page(GFP_KERNEL);
2043
2044                 if (!buf)
2045                         return 0;
2046                 while (off > 0) {
2047                         unsigned long n = off;
2048
2049                         if (n > PAGE_SIZE)
2050                                 n = PAGE_SIZE;
2051                         if (!dump_write(file, buf, n)) {
2052                                 ret = 0;
2053                                 break;
2054                         }
2055                         off -= n;
2056                 }
2057                 free_page((unsigned long)buf);
2058         }
2059         return ret;
2060 }
2061 EXPORT_SYMBOL(dump_seek);