jbd2: fix use after free in jbd2_journal_dirty_metadata()
[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/mount.h>
46 #include <linux/security.h>
47 #include <linux/syscalls.h>
48 #include <linux/tsacct_kern.h>
49 #include <linux/cn_proc.h>
50 #include <linux/audit.h>
51 #include <linux/tracehook.h>
52 #include <linux/kmod.h>
53 #include <linux/fsnotify.h>
54 #include <linux/fs_struct.h>
55 #include <linux/pipe_fs_i.h>
56 #include <linux/oom.h>
57 #include <linux/compat.h>
58
59 #include <asm/uaccess.h>
60 #include <asm/mmu_context.h>
61 #include <asm/tlb.h>
62 #include <asm/exec.h>
63
64 #include <trace/events/task.h>
65 #include "internal.h"
66
67 #include <trace/events/sched.h>
68
69 int core_uses_pid;
70 char core_pattern[CORENAME_MAX_SIZE] = "core";
71 unsigned int core_pipe_limit;
72 int suid_dumpable = 0;
73
74 struct core_name {
75         char *corename;
76         int used, size;
77 };
78 static atomic_t call_count = ATOMIC_INIT(1);
79
80 /* The maximal length of core_pattern is also specified in sysctl.c */
81
82 static LIST_HEAD(formats);
83 static DEFINE_RWLOCK(binfmt_lock);
84
85 void __register_binfmt(struct linux_binfmt * fmt, int insert)
86 {
87         BUG_ON(!fmt);
88         write_lock(&binfmt_lock);
89         insert ? list_add(&fmt->lh, &formats) :
90                  list_add_tail(&fmt->lh, &formats);
91         write_unlock(&binfmt_lock);
92 }
93
94 EXPORT_SYMBOL(__register_binfmt);
95
96 void unregister_binfmt(struct linux_binfmt * fmt)
97 {
98         write_lock(&binfmt_lock);
99         list_del(&fmt->lh);
100         write_unlock(&binfmt_lock);
101 }
102
103 EXPORT_SYMBOL(unregister_binfmt);
104
105 static inline void put_binfmt(struct linux_binfmt * fmt)
106 {
107         module_put(fmt->module);
108 }
109
110 /*
111  * Note that a shared library must be both readable and executable due to
112  * security reasons.
113  *
114  * Also note that we take the address to load from from the file itself.
115  */
116 SYSCALL_DEFINE1(uselib, const char __user *, library)
117 {
118         struct file *file;
119         char *tmp = getname(library);
120         int error = PTR_ERR(tmp);
121         static const struct open_flags uselib_flags = {
122                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
123                 .acc_mode = MAY_READ | MAY_EXEC | MAY_OPEN,
124                 .intent = LOOKUP_OPEN
125         };
126
127         if (IS_ERR(tmp))
128                 goto out;
129
130         file = do_filp_open(AT_FDCWD, tmp, &uselib_flags, LOOKUP_FOLLOW);
131         putname(tmp);
132         error = PTR_ERR(file);
133         if (IS_ERR(file))
134                 goto out;
135
136         error = -EINVAL;
137         if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
138                 goto exit;
139
140         error = -EACCES;
141         if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
142                 goto exit;
143
144         fsnotify_open(file);
145
146         error = -ENOEXEC;
147         if(file->f_op) {
148                 struct linux_binfmt * fmt;
149
150                 read_lock(&binfmt_lock);
151                 list_for_each_entry(fmt, &formats, lh) {
152                         if (!fmt->load_shlib)
153                                 continue;
154                         if (!try_module_get(fmt->module))
155                                 continue;
156                         read_unlock(&binfmt_lock);
157                         error = fmt->load_shlib(file);
158                         read_lock(&binfmt_lock);
159                         put_binfmt(fmt);
160                         if (error != -ENOEXEC)
161                                 break;
162                 }
163                 read_unlock(&binfmt_lock);
164         }
165 exit:
166         fput(file);
167 out:
168         return error;
169 }
170
171 #ifdef CONFIG_MMU
172 /*
173  * The nascent bprm->mm is not visible until exec_mmap() but it can
174  * use a lot of memory, account these pages in current->mm temporary
175  * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
176  * change the counter back via acct_arg_size(0).
177  */
178 static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
179 {
180         struct mm_struct *mm = current->mm;
181         long diff = (long)(pages - bprm->vma_pages);
182
183         if (!mm || !diff)
184                 return;
185
186         bprm->vma_pages = pages;
187         add_mm_counter(mm, MM_ANONPAGES, diff);
188 }
189
190 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
191                 int write)
192 {
193         struct page *page;
194         int ret;
195
196 #ifdef CONFIG_STACK_GROWSUP
197         if (write) {
198                 ret = expand_downwards(bprm->vma, pos);
199                 if (ret < 0)
200                         return NULL;
201         }
202 #endif
203         ret = get_user_pages(current, bprm->mm, pos,
204                         1, write, 1, &page, NULL);
205         if (ret <= 0)
206                 return NULL;
207
208         if (write) {
209                 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
210                 struct rlimit *rlim;
211
212                 acct_arg_size(bprm, size / PAGE_SIZE);
213
214                 /*
215                  * We've historically supported up to 32 pages (ARG_MAX)
216                  * of argument strings even with small stacks
217                  */
218                 if (size <= ARG_MAX)
219                         return page;
220
221                 /*
222                  * Limit to 1/4-th the stack size for the argv+env strings.
223                  * This ensures that:
224                  *  - the remaining binfmt code will not run out of stack space,
225                  *  - the program will have a reasonable amount of stack left
226                  *    to work from.
227                  */
228                 rlim = current->signal->rlim;
229                 if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) {
230                         put_page(page);
231                         return NULL;
232                 }
233         }
234
235         return page;
236 }
237
238 static void put_arg_page(struct page *page)
239 {
240         put_page(page);
241 }
242
243 static void free_arg_page(struct linux_binprm *bprm, int i)
244 {
245 }
246
247 static void free_arg_pages(struct linux_binprm *bprm)
248 {
249 }
250
251 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
252                 struct page *page)
253 {
254         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
255 }
256
257 static int __bprm_mm_init(struct linux_binprm *bprm)
258 {
259         int err;
260         struct vm_area_struct *vma = NULL;
261         struct mm_struct *mm = bprm->mm;
262
263         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
264         if (!vma)
265                 return -ENOMEM;
266
267         down_write(&mm->mmap_sem);
268         vma->vm_mm = mm;
269
270         /*
271          * Place the stack at the largest stack address the architecture
272          * supports. Later, we'll move this to an appropriate place. We don't
273          * use STACK_TOP because that can depend on attributes which aren't
274          * configured yet.
275          */
276         BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
277         vma->vm_end = STACK_TOP_MAX;
278         vma->vm_start = vma->vm_end - PAGE_SIZE;
279         vma->vm_flags = VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
280         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
281         INIT_LIST_HEAD(&vma->anon_vma_chain);
282
283         err = security_file_mmap(NULL, 0, 0, 0, vma->vm_start, 1);
284         if (err)
285                 goto err;
286
287         err = insert_vm_struct(mm, vma);
288         if (err)
289                 goto err;
290
291         mm->stack_vm = mm->total_vm = 1;
292         up_write(&mm->mmap_sem);
293         bprm->p = vma->vm_end - sizeof(void *);
294         return 0;
295 err:
296         up_write(&mm->mmap_sem);
297         bprm->vma = NULL;
298         kmem_cache_free(vm_area_cachep, vma);
299         return err;
300 }
301
302 static bool valid_arg_len(struct linux_binprm *bprm, long len)
303 {
304         return len <= MAX_ARG_STRLEN;
305 }
306
307 #else
308
309 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
310 {
311 }
312
313 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
314                 int write)
315 {
316         struct page *page;
317
318         page = bprm->page[pos / PAGE_SIZE];
319         if (!page && write) {
320                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
321                 if (!page)
322                         return NULL;
323                 bprm->page[pos / PAGE_SIZE] = page;
324         }
325
326         return page;
327 }
328
329 static void put_arg_page(struct page *page)
330 {
331 }
332
333 static void free_arg_page(struct linux_binprm *bprm, int i)
334 {
335         if (bprm->page[i]) {
336                 __free_page(bprm->page[i]);
337                 bprm->page[i] = NULL;
338         }
339 }
340
341 static void free_arg_pages(struct linux_binprm *bprm)
342 {
343         int i;
344
345         for (i = 0; i < MAX_ARG_PAGES; i++)
346                 free_arg_page(bprm, i);
347 }
348
349 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
350                 struct page *page)
351 {
352 }
353
354 static int __bprm_mm_init(struct linux_binprm *bprm)
355 {
356         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
357         return 0;
358 }
359
360 static bool valid_arg_len(struct linux_binprm *bprm, long len)
361 {
362         return len <= bprm->p;
363 }
364
365 #endif /* CONFIG_MMU */
366
367 /*
368  * Create a new mm_struct and populate it with a temporary stack
369  * vm_area_struct.  We don't have enough context at this point to set the stack
370  * flags, permissions, and offset, so we use temporary values.  We'll update
371  * them later in setup_arg_pages().
372  */
373 int bprm_mm_init(struct linux_binprm *bprm)
374 {
375         int err;
376         struct mm_struct *mm = NULL;
377
378         bprm->mm = mm = mm_alloc();
379         err = -ENOMEM;
380         if (!mm)
381                 goto err;
382
383         err = init_new_context(current, mm);
384         if (err)
385                 goto err;
386
387         err = __bprm_mm_init(bprm);
388         if (err)
389                 goto err;
390
391         return 0;
392
393 err:
394         if (mm) {
395                 bprm->mm = NULL;
396                 mmdrop(mm);
397         }
398
399         return err;
400 }
401
402 struct user_arg_ptr {
403 #ifdef CONFIG_COMPAT
404         bool is_compat;
405 #endif
406         union {
407                 const char __user *const __user *native;
408 #ifdef CONFIG_COMPAT
409                 compat_uptr_t __user *compat;
410 #endif
411         } ptr;
412 };
413
414 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
415 {
416         const char __user *native;
417
418 #ifdef CONFIG_COMPAT
419         if (unlikely(argv.is_compat)) {
420                 compat_uptr_t compat;
421
422                 if (get_user(compat, argv.ptr.compat + nr))
423                         return ERR_PTR(-EFAULT);
424
425                 return compat_ptr(compat);
426         }
427 #endif
428
429         if (get_user(native, argv.ptr.native + nr))
430                 return ERR_PTR(-EFAULT);
431
432         return native;
433 }
434
435 /*
436  * count() counts the number of strings in array ARGV.
437  */
438 static int count(struct user_arg_ptr argv, int max)
439 {
440         int i = 0;
441
442         if (argv.ptr.native != NULL) {
443                 for (;;) {
444                         const char __user *p = get_user_arg_ptr(argv, i);
445
446                         if (!p)
447                                 break;
448
449                         if (IS_ERR(p))
450                                 return -EFAULT;
451
452                         if (i++ >= max)
453                                 return -E2BIG;
454
455                         if (fatal_signal_pending(current))
456                                 return -ERESTARTNOHAND;
457                         cond_resched();
458                 }
459         }
460         return i;
461 }
462
463 /*
464  * 'copy_strings()' copies argument/environment strings from the old
465  * processes's memory to the new process's stack.  The call to get_user_pages()
466  * ensures the destination page is created and not swapped out.
467  */
468 static int copy_strings(int argc, struct user_arg_ptr argv,
469                         struct linux_binprm *bprm)
470 {
471         struct page *kmapped_page = NULL;
472         char *kaddr = NULL;
473         unsigned long kpos = 0;
474         int ret;
475
476         while (argc-- > 0) {
477                 const char __user *str;
478                 int len;
479                 unsigned long pos;
480
481                 ret = -EFAULT;
482                 str = get_user_arg_ptr(argv, argc);
483                 if (IS_ERR(str))
484                         goto out;
485
486                 len = strnlen_user(str, MAX_ARG_STRLEN);
487                 if (!len)
488                         goto out;
489
490                 ret = -E2BIG;
491                 if (!valid_arg_len(bprm, len))
492                         goto out;
493
494                 /* We're going to work our way backwords. */
495                 pos = bprm->p;
496                 str += len;
497                 bprm->p -= len;
498
499                 while (len > 0) {
500                         int offset, bytes_to_copy;
501
502                         if (fatal_signal_pending(current)) {
503                                 ret = -ERESTARTNOHAND;
504                                 goto out;
505                         }
506                         cond_resched();
507
508                         offset = pos % PAGE_SIZE;
509                         if (offset == 0)
510                                 offset = PAGE_SIZE;
511
512                         bytes_to_copy = offset;
513                         if (bytes_to_copy > len)
514                                 bytes_to_copy = len;
515
516                         offset -= bytes_to_copy;
517                         pos -= bytes_to_copy;
518                         str -= bytes_to_copy;
519                         len -= bytes_to_copy;
520
521                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
522                                 struct page *page;
523
524                                 page = get_arg_page(bprm, pos, 1);
525                                 if (!page) {
526                                         ret = -E2BIG;
527                                         goto out;
528                                 }
529
530                                 if (kmapped_page) {
531                                         flush_kernel_dcache_page(kmapped_page);
532                                         kunmap(kmapped_page);
533                                         put_arg_page(kmapped_page);
534                                 }
535                                 kmapped_page = page;
536                                 kaddr = kmap(kmapped_page);
537                                 kpos = pos & PAGE_MASK;
538                                 flush_arg_page(bprm, kpos, kmapped_page);
539                         }
540                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
541                                 ret = -EFAULT;
542                                 goto out;
543                         }
544                 }
545         }
546         ret = 0;
547 out:
548         if (kmapped_page) {
549                 flush_kernel_dcache_page(kmapped_page);
550                 kunmap(kmapped_page);
551                 put_arg_page(kmapped_page);
552         }
553         return ret;
554 }
555
556 /*
557  * Like copy_strings, but get argv and its values from kernel memory.
558  */
559 int copy_strings_kernel(int argc, const char *const *__argv,
560                         struct linux_binprm *bprm)
561 {
562         int r;
563         mm_segment_t oldfs = get_fs();
564         struct user_arg_ptr argv = {
565                 .ptr.native = (const char __user *const  __user *)__argv,
566         };
567
568         set_fs(KERNEL_DS);
569         r = copy_strings(argc, argv, bprm);
570         set_fs(oldfs);
571
572         return r;
573 }
574 EXPORT_SYMBOL(copy_strings_kernel);
575
576 #ifdef CONFIG_MMU
577
578 /*
579  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
580  * the binfmt code determines where the new stack should reside, we shift it to
581  * its final location.  The process proceeds as follows:
582  *
583  * 1) Use shift to calculate the new vma endpoints.
584  * 2) Extend vma to cover both the old and new ranges.  This ensures the
585  *    arguments passed to subsequent functions are consistent.
586  * 3) Move vma's page tables to the new range.
587  * 4) Free up any cleared pgd range.
588  * 5) Shrink the vma to cover only the new range.
589  */
590 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
591 {
592         struct mm_struct *mm = vma->vm_mm;
593         unsigned long old_start = vma->vm_start;
594         unsigned long old_end = vma->vm_end;
595         unsigned long length = old_end - old_start;
596         unsigned long new_start = old_start - shift;
597         unsigned long new_end = old_end - shift;
598         struct mmu_gather tlb;
599
600         BUG_ON(new_start > new_end);
601
602         /*
603          * ensure there are no vmas between where we want to go
604          * and where we are
605          */
606         if (vma != find_vma(mm, new_start))
607                 return -EFAULT;
608
609         /*
610          * cover the whole range: [new_start, old_end)
611          */
612         if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
613                 return -ENOMEM;
614
615         /*
616          * move the page tables downwards, on failure we rely on
617          * process cleanup to remove whatever mess we made.
618          */
619         if (length != move_page_tables(vma, old_start,
620                                        vma, new_start, length))
621                 return -ENOMEM;
622
623         lru_add_drain();
624         tlb_gather_mmu(&tlb, mm, 0);
625         if (new_end > old_start) {
626                 /*
627                  * when the old and new regions overlap clear from new_end.
628                  */
629                 free_pgd_range(&tlb, new_end, old_end, new_end,
630                         vma->vm_next ? vma->vm_next->vm_start : 0);
631         } else {
632                 /*
633                  * otherwise, clean from old_start; this is done to not touch
634                  * the address space in [new_end, old_start) some architectures
635                  * have constraints on va-space that make this illegal (IA64) -
636                  * for the others its just a little faster.
637                  */
638                 free_pgd_range(&tlb, old_start, old_end, new_end,
639                         vma->vm_next ? vma->vm_next->vm_start : 0);
640         }
641         tlb_finish_mmu(&tlb, new_end, old_end);
642
643         /*
644          * Shrink the vma to just the new range.  Always succeeds.
645          */
646         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
647
648         return 0;
649 }
650
651 /*
652  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
653  * the stack is optionally relocated, and some extra space is added.
654  */
655 int setup_arg_pages(struct linux_binprm *bprm,
656                     unsigned long stack_top,
657                     int executable_stack)
658 {
659         unsigned long ret;
660         unsigned long stack_shift;
661         struct mm_struct *mm = current->mm;
662         struct vm_area_struct *vma = bprm->vma;
663         struct vm_area_struct *prev = NULL;
664         unsigned long vm_flags;
665         unsigned long stack_base;
666         unsigned long stack_size;
667         unsigned long stack_expand;
668         unsigned long rlim_stack;
669
670 #ifdef CONFIG_STACK_GROWSUP
671         /* Limit stack size to 1GB */
672         stack_base = rlimit_max(RLIMIT_STACK);
673         if (stack_base > (1 << 30))
674                 stack_base = 1 << 30;
675
676         /* Make sure we didn't let the argument array grow too large. */
677         if (vma->vm_end - vma->vm_start > stack_base)
678                 return -ENOMEM;
679
680         stack_base = PAGE_ALIGN(stack_top - stack_base);
681
682         stack_shift = vma->vm_start - stack_base;
683         mm->arg_start = bprm->p - stack_shift;
684         bprm->p = vma->vm_end - stack_shift;
685 #else
686         stack_top = arch_align_stack(stack_top);
687         stack_top = PAGE_ALIGN(stack_top);
688
689         if (unlikely(stack_top < mmap_min_addr) ||
690             unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
691                 return -ENOMEM;
692
693         stack_shift = vma->vm_end - stack_top;
694
695         bprm->p -= stack_shift;
696         mm->arg_start = bprm->p;
697 #endif
698
699         if (bprm->loader)
700                 bprm->loader -= stack_shift;
701         bprm->exec -= stack_shift;
702
703         down_write(&mm->mmap_sem);
704         vm_flags = VM_STACK_FLAGS;
705
706         /*
707          * Adjust stack execute permissions; explicitly enable for
708          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
709          * (arch default) otherwise.
710          */
711         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
712                 vm_flags |= VM_EXEC;
713         else if (executable_stack == EXSTACK_DISABLE_X)
714                 vm_flags &= ~VM_EXEC;
715         vm_flags |= mm->def_flags;
716         vm_flags |= VM_STACK_INCOMPLETE_SETUP;
717
718         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
719                         vm_flags);
720         if (ret)
721                 goto out_unlock;
722         BUG_ON(prev != vma);
723
724         /* Move stack pages down in memory. */
725         if (stack_shift) {
726                 ret = shift_arg_pages(vma, stack_shift);
727                 if (ret)
728                         goto out_unlock;
729         }
730
731         /* mprotect_fixup is overkill to remove the temporary stack flags */
732         vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
733
734         stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
735         stack_size = vma->vm_end - vma->vm_start;
736         /*
737          * Align this down to a page boundary as expand_stack
738          * will align it up.
739          */
740         rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
741 #ifdef CONFIG_STACK_GROWSUP
742         if (stack_size + stack_expand > rlim_stack)
743                 stack_base = vma->vm_start + rlim_stack;
744         else
745                 stack_base = vma->vm_end + stack_expand;
746 #else
747         if (stack_size + stack_expand > rlim_stack)
748                 stack_base = vma->vm_end - rlim_stack;
749         else
750                 stack_base = vma->vm_start - stack_expand;
751 #endif
752         current->mm->start_stack = bprm->p;
753         ret = expand_stack(vma, stack_base);
754         if (ret)
755                 ret = -EFAULT;
756
757 out_unlock:
758         up_write(&mm->mmap_sem);
759         return ret;
760 }
761 EXPORT_SYMBOL(setup_arg_pages);
762
763 #endif /* CONFIG_MMU */
764
765 struct file *open_exec(const char *name)
766 {
767         struct file *file;
768         int err;
769         static const struct open_flags open_exec_flags = {
770                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
771                 .acc_mode = MAY_EXEC | MAY_OPEN,
772                 .intent = LOOKUP_OPEN
773         };
774
775         file = do_filp_open(AT_FDCWD, name, &open_exec_flags, LOOKUP_FOLLOW);
776         if (IS_ERR(file))
777                 goto out;
778
779         err = -EACCES;
780         if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
781                 goto exit;
782
783         if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
784                 goto exit;
785
786         fsnotify_open(file);
787
788         err = deny_write_access(file);
789         if (err)
790                 goto exit;
791
792 out:
793         return file;
794
795 exit:
796         fput(file);
797         return ERR_PTR(err);
798 }
799 EXPORT_SYMBOL(open_exec);
800
801 int kernel_read(struct file *file, loff_t offset,
802                 char *addr, unsigned long count)
803 {
804         mm_segment_t old_fs;
805         loff_t pos = offset;
806         int result;
807
808         old_fs = get_fs();
809         set_fs(get_ds());
810         /* The cast to a user pointer is valid due to the set_fs() */
811         result = vfs_read(file, (void __user *)addr, count, &pos);
812         set_fs(old_fs);
813         return result;
814 }
815
816 EXPORT_SYMBOL(kernel_read);
817
818 static int exec_mmap(struct mm_struct *mm)
819 {
820         struct task_struct *tsk;
821         struct mm_struct * old_mm, *active_mm;
822
823         /* Notify parent that we're no longer interested in the old VM */
824         tsk = current;
825         old_mm = current->mm;
826         mm_release(tsk, old_mm);
827
828         if (old_mm) {
829                 sync_mm_rss(old_mm);
830                 /*
831                  * Make sure that if there is a core dump in progress
832                  * for the old mm, we get out and die instead of going
833                  * through with the exec.  We must hold mmap_sem around
834                  * checking core_state and changing tsk->mm.
835                  */
836                 down_read(&old_mm->mmap_sem);
837                 if (unlikely(old_mm->core_state)) {
838                         up_read(&old_mm->mmap_sem);
839                         return -EINTR;
840                 }
841         }
842         task_lock(tsk);
843         active_mm = tsk->active_mm;
844         tsk->mm = mm;
845         tsk->active_mm = mm;
846         activate_mm(active_mm, mm);
847         task_unlock(tsk);
848         arch_pick_mmap_layout(mm);
849         if (old_mm) {
850                 up_read(&old_mm->mmap_sem);
851                 BUG_ON(active_mm != old_mm);
852                 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
853                 mm_update_next_owner(old_mm);
854                 mmput(old_mm);
855                 return 0;
856         }
857         mmdrop(active_mm);
858         return 0;
859 }
860
861 /*
862  * This function makes sure the current process has its own signal table,
863  * so that flush_signal_handlers can later reset the handlers without
864  * disturbing other processes.  (Other processes might share the signal
865  * table via the CLONE_SIGHAND option to clone().)
866  */
867 static int de_thread(struct task_struct *tsk)
868 {
869         struct signal_struct *sig = tsk->signal;
870         struct sighand_struct *oldsighand = tsk->sighand;
871         spinlock_t *lock = &oldsighand->siglock;
872
873         if (thread_group_empty(tsk))
874                 goto no_thread_group;
875
876         /*
877          * Kill all other threads in the thread group.
878          */
879         spin_lock_irq(lock);
880         if (signal_group_exit(sig)) {
881                 /*
882                  * Another group action in progress, just
883                  * return so that the signal is processed.
884                  */
885                 spin_unlock_irq(lock);
886                 return -EAGAIN;
887         }
888
889         sig->group_exit_task = tsk;
890         sig->notify_count = zap_other_threads(tsk);
891         if (!thread_group_leader(tsk))
892                 sig->notify_count--;
893
894         while (sig->notify_count) {
895                 __set_current_state(TASK_UNINTERRUPTIBLE);
896                 spin_unlock_irq(lock);
897                 schedule();
898                 spin_lock_irq(lock);
899         }
900         spin_unlock_irq(lock);
901
902         /*
903          * At this point all other threads have exited, all we have to
904          * do is to wait for the thread group leader to become inactive,
905          * and to assume its PID:
906          */
907         if (!thread_group_leader(tsk)) {
908                 struct task_struct *leader = tsk->group_leader;
909
910                 sig->notify_count = -1; /* for exit_notify() */
911                 for (;;) {
912                         write_lock_irq(&tasklist_lock);
913                         if (likely(leader->exit_state))
914                                 break;
915                         __set_current_state(TASK_UNINTERRUPTIBLE);
916                         write_unlock_irq(&tasklist_lock);
917                         schedule();
918                 }
919
920                 /*
921                  * The only record we have of the real-time age of a
922                  * process, regardless of execs it's done, is start_time.
923                  * All the past CPU time is accumulated in signal_struct
924                  * from sister threads now dead.  But in this non-leader
925                  * exec, nothing survives from the original leader thread,
926                  * whose birth marks the true age of this process now.
927                  * When we take on its identity by switching to its PID, we
928                  * also take its birthdate (always earlier than our own).
929                  */
930                 tsk->start_time = leader->start_time;
931
932                 BUG_ON(!same_thread_group(leader, tsk));
933                 BUG_ON(has_group_leader_pid(tsk));
934                 /*
935                  * An exec() starts a new thread group with the
936                  * TGID of the previous thread group. Rehash the
937                  * two threads with a switched PID, and release
938                  * the former thread group leader:
939                  */
940
941                 /* Become a process group leader with the old leader's pid.
942                  * The old leader becomes a thread of the this thread group.
943                  * Note: The old leader also uses this pid until release_task
944                  *       is called.  Odd but simple and correct.
945                  */
946                 detach_pid(tsk, PIDTYPE_PID);
947                 tsk->pid = leader->pid;
948                 attach_pid(tsk, PIDTYPE_PID,  task_pid(leader));
949                 transfer_pid(leader, tsk, PIDTYPE_PGID);
950                 transfer_pid(leader, tsk, PIDTYPE_SID);
951
952                 list_replace_rcu(&leader->tasks, &tsk->tasks);
953                 list_replace_init(&leader->sibling, &tsk->sibling);
954
955                 tsk->group_leader = tsk;
956                 leader->group_leader = tsk;
957
958                 tsk->exit_signal = SIGCHLD;
959                 leader->exit_signal = -1;
960
961                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
962                 leader->exit_state = EXIT_DEAD;
963
964                 /*
965                  * We are going to release_task()->ptrace_unlink() silently,
966                  * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
967                  * the tracer wont't block again waiting for this thread.
968                  */
969                 if (unlikely(leader->ptrace))
970                         __wake_up_parent(leader, leader->parent);
971                 write_unlock_irq(&tasklist_lock);
972
973                 release_task(leader);
974         }
975
976         sig->group_exit_task = NULL;
977         sig->notify_count = 0;
978
979 no_thread_group:
980         /* we have changed execution domain */
981         tsk->exit_signal = SIGCHLD;
982
983         exit_itimers(sig);
984         flush_itimer_signals();
985
986         if (atomic_read(&oldsighand->count) != 1) {
987                 struct sighand_struct *newsighand;
988                 /*
989                  * This ->sighand is shared with the CLONE_SIGHAND
990                  * but not CLONE_THREAD task, switch to the new one.
991                  */
992                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
993                 if (!newsighand)
994                         return -ENOMEM;
995
996                 atomic_set(&newsighand->count, 1);
997                 memcpy(newsighand->action, oldsighand->action,
998                        sizeof(newsighand->action));
999
1000                 write_lock_irq(&tasklist_lock);
1001                 spin_lock(&oldsighand->siglock);
1002                 rcu_assign_pointer(tsk->sighand, newsighand);
1003                 spin_unlock(&oldsighand->siglock);
1004                 write_unlock_irq(&tasklist_lock);
1005
1006                 __cleanup_sighand(oldsighand);
1007         }
1008
1009         BUG_ON(!thread_group_leader(tsk));
1010         return 0;
1011 }
1012
1013 /*
1014  * These functions flushes out all traces of the currently running executable
1015  * so that a new one can be started
1016  */
1017 static void flush_old_files(struct files_struct * files)
1018 {
1019         long j = -1;
1020         struct fdtable *fdt;
1021
1022         spin_lock(&files->file_lock);
1023         for (;;) {
1024                 unsigned long set, i;
1025
1026                 j++;
1027                 i = j * BITS_PER_LONG;
1028                 fdt = files_fdtable(files);
1029                 if (i >= fdt->max_fds)
1030                         break;
1031                 set = fdt->close_on_exec[j];
1032                 if (!set)
1033                         continue;
1034                 fdt->close_on_exec[j] = 0;
1035                 spin_unlock(&files->file_lock);
1036                 for ( ; set ; i++,set >>= 1) {
1037                         if (set & 1) {
1038                                 sys_close(i);
1039                         }
1040                 }
1041                 spin_lock(&files->file_lock);
1042
1043         }
1044         spin_unlock(&files->file_lock);
1045 }
1046
1047 char *get_task_comm(char *buf, struct task_struct *tsk)
1048 {
1049         /* buf must be at least sizeof(tsk->comm) in size */
1050         task_lock(tsk);
1051         strncpy(buf, tsk->comm, sizeof(tsk->comm));
1052         task_unlock(tsk);
1053         return buf;
1054 }
1055 EXPORT_SYMBOL_GPL(get_task_comm);
1056
1057 void set_task_comm(struct task_struct *tsk, char *buf)
1058 {
1059         task_lock(tsk);
1060
1061         trace_task_rename(tsk, buf);
1062
1063         /*
1064          * Threads may access current->comm without holding
1065          * the task lock, so write the string carefully.
1066          * Readers without a lock may see incomplete new
1067          * names but are safe from non-terminating string reads.
1068          */
1069         memset(tsk->comm, 0, TASK_COMM_LEN);
1070         wmb();
1071         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1072         task_unlock(tsk);
1073         perf_event_comm(tsk);
1074 }
1075
1076 static void filename_to_taskname(char *tcomm, const char *fn, unsigned int len)
1077 {
1078         int i, ch;
1079
1080         /* Copies the binary name from after last slash */
1081         for (i = 0; (ch = *(fn++)) != '\0';) {
1082                 if (ch == '/')
1083                         i = 0; /* overwrite what we wrote */
1084                 else
1085                         if (i < len - 1)
1086                                 tcomm[i++] = ch;
1087         }
1088         tcomm[i] = '\0';
1089 }
1090
1091 int flush_old_exec(struct linux_binprm * bprm)
1092 {
1093         int retval;
1094
1095         /*
1096          * Make sure we have a private signal table and that
1097          * we are unassociated from the previous thread group.
1098          */
1099         retval = de_thread(current);
1100         if (retval)
1101                 goto out;
1102
1103         set_mm_exe_file(bprm->mm, bprm->file);
1104
1105         filename_to_taskname(bprm->tcomm, bprm->filename, sizeof(bprm->tcomm));
1106         /*
1107          * Release all of the old mmap stuff
1108          */
1109         acct_arg_size(bprm, 0);
1110         retval = exec_mmap(bprm->mm);
1111         if (retval)
1112                 goto out;
1113
1114         bprm->mm = NULL;                /* We're using it now */
1115
1116         set_fs(USER_DS);
1117         current->flags &=
1118                 ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD | PF_NOFREEZE);
1119         flush_thread();
1120         current->personality &= ~bprm->per_clear;
1121
1122         return 0;
1123
1124 out:
1125         return retval;
1126 }
1127 EXPORT_SYMBOL(flush_old_exec);
1128
1129 void would_dump(struct linux_binprm *bprm, struct file *file)
1130 {
1131         if (inode_permission(file->f_path.dentry->d_inode, MAY_READ) < 0)
1132                 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1133 }
1134 EXPORT_SYMBOL(would_dump);
1135
1136 void setup_new_exec(struct linux_binprm * bprm)
1137 {
1138         arch_pick_mmap_layout(current->mm);
1139
1140         /* This is the point of no return */
1141         current->sas_ss_sp = current->sas_ss_size = 0;
1142
1143         if (current_euid() == current_uid() && current_egid() == current_gid())
1144                 set_dumpable(current->mm, 1);
1145         else
1146                 set_dumpable(current->mm, suid_dumpable);
1147
1148         set_task_comm(current, bprm->tcomm);
1149
1150         /* Set the new mm task size. We have to do that late because it may
1151          * depend on TIF_32BIT which is only updated in flush_thread() on
1152          * some architectures like powerpc
1153          */
1154         current->mm->task_size = TASK_SIZE;
1155
1156         /* install the new credentials */
1157         if (bprm->cred->uid != current_euid() ||
1158             bprm->cred->gid != current_egid()) {
1159                 current->pdeath_signal = 0;
1160         } else {
1161                 would_dump(bprm, bprm->file);
1162                 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
1163                         set_dumpable(current->mm, suid_dumpable);
1164         }
1165
1166         /*
1167          * Flush performance counters when crossing a
1168          * security domain:
1169          */
1170         if (!get_dumpable(current->mm))
1171                 perf_event_exit_task(current);
1172
1173         /* An exec changes our domain. We are no longer part of the thread
1174            group */
1175
1176         current->self_exec_id++;
1177                         
1178         flush_signal_handlers(current, 0);
1179         flush_old_files(current->files);
1180 }
1181 EXPORT_SYMBOL(setup_new_exec);
1182
1183 /*
1184  * Prepare credentials and lock ->cred_guard_mutex.
1185  * install_exec_creds() commits the new creds and drops the lock.
1186  * Or, if exec fails before, free_bprm() should release ->cred and
1187  * and unlock.
1188  */
1189 int prepare_bprm_creds(struct linux_binprm *bprm)
1190 {
1191         if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1192                 return -ERESTARTNOINTR;
1193
1194         bprm->cred = prepare_exec_creds();
1195         if (likely(bprm->cred))
1196                 return 0;
1197
1198         mutex_unlock(&current->signal->cred_guard_mutex);
1199         return -ENOMEM;
1200 }
1201
1202 void free_bprm(struct linux_binprm *bprm)
1203 {
1204         free_arg_pages(bprm);
1205         if (bprm->cred) {
1206                 mutex_unlock(&current->signal->cred_guard_mutex);
1207                 abort_creds(bprm->cred);
1208         }
1209         /* If a binfmt changed the interp, free it. */
1210         if (bprm->interp != bprm->filename)
1211                 kfree(bprm->interp);
1212         kfree(bprm);
1213 }
1214
1215 int bprm_change_interp(char *interp, struct linux_binprm *bprm)
1216 {
1217         /* If a binfmt changed the interp, free it first. */
1218         if (bprm->interp != bprm->filename)
1219                 kfree(bprm->interp);
1220         bprm->interp = kstrdup(interp, GFP_KERNEL);
1221         if (!bprm->interp)
1222                 return -ENOMEM;
1223         return 0;
1224 }
1225 EXPORT_SYMBOL(bprm_change_interp);
1226
1227 /*
1228  * install the new credentials for this executable
1229  */
1230 void install_exec_creds(struct linux_binprm *bprm)
1231 {
1232         security_bprm_committing_creds(bprm);
1233
1234         commit_creds(bprm->cred);
1235         bprm->cred = NULL;
1236         /*
1237          * cred_guard_mutex must be held at least to this point to prevent
1238          * ptrace_attach() from altering our determination of the task's
1239          * credentials; any time after this it may be unlocked.
1240          */
1241         security_bprm_committed_creds(bprm);
1242         mutex_unlock(&current->signal->cred_guard_mutex);
1243 }
1244 EXPORT_SYMBOL(install_exec_creds);
1245
1246 /*
1247  * determine how safe it is to execute the proposed program
1248  * - the caller must hold ->cred_guard_mutex to protect against
1249  *   PTRACE_ATTACH
1250  */
1251 static int check_unsafe_exec(struct linux_binprm *bprm)
1252 {
1253         struct task_struct *p = current, *t;
1254         unsigned n_fs;
1255         int res = 0;
1256
1257         if (p->ptrace) {
1258                 if (p->ptrace & PT_PTRACE_CAP)
1259                         bprm->unsafe |= LSM_UNSAFE_PTRACE_CAP;
1260                 else
1261                         bprm->unsafe |= LSM_UNSAFE_PTRACE;
1262         }
1263
1264         n_fs = 1;
1265         spin_lock(&p->fs->lock);
1266         rcu_read_lock();
1267         for (t = next_thread(p); t != p; t = next_thread(t)) {
1268                 if (t->fs == p->fs)
1269                         n_fs++;
1270         }
1271         rcu_read_unlock();
1272
1273         if (p->fs->users > n_fs) {
1274                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1275         } else {
1276                 res = -EAGAIN;
1277                 if (!p->fs->in_exec) {
1278                         p->fs->in_exec = 1;
1279                         res = 1;
1280                 }
1281         }
1282         spin_unlock(&p->fs->lock);
1283
1284         return res;
1285 }
1286
1287 /* 
1288  * Fill the binprm structure from the inode. 
1289  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1290  *
1291  * This may be called multiple times for binary chains (scripts for example).
1292  */
1293 int prepare_binprm(struct linux_binprm *bprm)
1294 {
1295         umode_t mode;
1296         struct inode * inode = bprm->file->f_path.dentry->d_inode;
1297         int retval;
1298
1299         mode = inode->i_mode;
1300         if (bprm->file->f_op == NULL)
1301                 return -EACCES;
1302
1303         /* clear any previous set[ug]id data from a previous binary */
1304         bprm->cred->euid = current_euid();
1305         bprm->cred->egid = current_egid();
1306
1307         if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
1308                 /* Set-uid? */
1309                 if (mode & S_ISUID) {
1310                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1311                         bprm->cred->euid = inode->i_uid;
1312                 }
1313
1314                 /* Set-gid? */
1315                 /*
1316                  * If setgid is set but no group execute bit then this
1317                  * is a candidate for mandatory locking, not a setgid
1318                  * executable.
1319                  */
1320                 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1321                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1322                         bprm->cred->egid = inode->i_gid;
1323                 }
1324         }
1325
1326         /* fill in binprm security blob */
1327         retval = security_bprm_set_creds(bprm);
1328         if (retval)
1329                 return retval;
1330         bprm->cred_prepared = 1;
1331
1332         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1333         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1334 }
1335
1336 EXPORT_SYMBOL(prepare_binprm);
1337
1338 /*
1339  * Arguments are '\0' separated strings found at the location bprm->p
1340  * points to; chop off the first by relocating brpm->p to right after
1341  * the first '\0' encountered.
1342  */
1343 int remove_arg_zero(struct linux_binprm *bprm)
1344 {
1345         int ret = 0;
1346         unsigned long offset;
1347         char *kaddr;
1348         struct page *page;
1349
1350         if (!bprm->argc)
1351                 return 0;
1352
1353         do {
1354                 offset = bprm->p & ~PAGE_MASK;
1355                 page = get_arg_page(bprm, bprm->p, 0);
1356                 if (!page) {
1357                         ret = -EFAULT;
1358                         goto out;
1359                 }
1360                 kaddr = kmap_atomic(page);
1361
1362                 for (; offset < PAGE_SIZE && kaddr[offset];
1363                                 offset++, bprm->p++)
1364                         ;
1365
1366                 kunmap_atomic(kaddr);
1367                 put_arg_page(page);
1368
1369                 if (offset == PAGE_SIZE)
1370                         free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1371         } while (offset == PAGE_SIZE);
1372
1373         bprm->p++;
1374         bprm->argc--;
1375         ret = 0;
1376
1377 out:
1378         return ret;
1379 }
1380 EXPORT_SYMBOL(remove_arg_zero);
1381
1382 /*
1383  * cycle the list of binary formats handler, until one recognizes the image
1384  */
1385 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1386 {
1387         unsigned int depth = bprm->recursion_depth;
1388         int try,retval;
1389         struct linux_binfmt *fmt;
1390         pid_t old_pid, old_vpid;
1391
1392         retval = security_bprm_check(bprm);
1393         if (retval)
1394                 return retval;
1395
1396         retval = audit_bprm(bprm);
1397         if (retval)
1398                 return retval;
1399
1400         /* Need to fetch pid before load_binary changes it */
1401         old_pid = current->pid;
1402         rcu_read_lock();
1403         old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1404         rcu_read_unlock();
1405
1406         retval = -ENOENT;
1407         for (try=0; try<2; try++) {
1408                 read_lock(&binfmt_lock);
1409                 list_for_each_entry(fmt, &formats, lh) {
1410                         int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1411                         if (!fn)
1412                                 continue;
1413                         if (!try_module_get(fmt->module))
1414                                 continue;
1415                         read_unlock(&binfmt_lock);
1416                         retval = fn(bprm, regs);
1417                         /*
1418                          * Restore the depth counter to its starting value
1419                          * in this call, so we don't have to rely on every
1420                          * load_binary function to restore it on return.
1421                          */
1422                         bprm->recursion_depth = depth;
1423                         if (retval >= 0) {
1424                                 if (depth == 0) {
1425                                         trace_sched_process_exec(current, old_pid, bprm);
1426                                         ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1427                                 }
1428                                 put_binfmt(fmt);
1429                                 allow_write_access(bprm->file);
1430                                 if (bprm->file)
1431                                         fput(bprm->file);
1432                                 bprm->file = NULL;
1433                                 current->did_exec = 1;
1434                                 proc_exec_connector(current);
1435                                 return retval;
1436                         }
1437                         read_lock(&binfmt_lock);
1438                         put_binfmt(fmt);
1439                         if (retval != -ENOEXEC || bprm->mm == NULL)
1440                                 break;
1441                         if (!bprm->file) {
1442                                 read_unlock(&binfmt_lock);
1443                                 return retval;
1444                         }
1445                 }
1446                 read_unlock(&binfmt_lock);
1447 #ifdef CONFIG_MODULES
1448                 if (retval != -ENOEXEC || bprm->mm == NULL) {
1449                         break;
1450                 } else {
1451 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1452                         if (printable(bprm->buf[0]) &&
1453                             printable(bprm->buf[1]) &&
1454                             printable(bprm->buf[2]) &&
1455                             printable(bprm->buf[3]))
1456                                 break; /* -ENOEXEC */
1457                         if (try)
1458                                 break; /* -ENOEXEC */
1459                         request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1460                 }
1461 #else
1462                 break;
1463 #endif
1464         }
1465         return retval;
1466 }
1467
1468 EXPORT_SYMBOL(search_binary_handler);
1469
1470 /*
1471  * sys_execve() executes a new program.
1472  */
1473 static int do_execve_common(const char *filename,
1474                                 struct user_arg_ptr argv,
1475                                 struct user_arg_ptr envp,
1476                                 struct pt_regs *regs)
1477 {
1478         struct linux_binprm *bprm;
1479         struct file *file;
1480         struct files_struct *displaced;
1481         bool clear_in_exec;
1482         int retval;
1483         const struct cred *cred = current_cred();
1484
1485         /*
1486          * We move the actual failure in case of RLIMIT_NPROC excess from
1487          * set*uid() to execve() because too many poorly written programs
1488          * don't check setuid() return code.  Here we additionally recheck
1489          * whether NPROC limit is still exceeded.
1490          */
1491         if ((current->flags & PF_NPROC_EXCEEDED) &&
1492             atomic_read(&cred->user->processes) > rlimit(RLIMIT_NPROC)) {
1493                 retval = -EAGAIN;
1494                 goto out_ret;
1495         }
1496
1497         /* We're below the limit (still or again), so we don't want to make
1498          * further execve() calls fail. */
1499         current->flags &= ~PF_NPROC_EXCEEDED;
1500
1501         retval = unshare_files(&displaced);
1502         if (retval)
1503                 goto out_ret;
1504
1505         retval = -ENOMEM;
1506         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1507         if (!bprm)
1508                 goto out_files;
1509
1510         retval = prepare_bprm_creds(bprm);
1511         if (retval)
1512                 goto out_free;
1513
1514         retval = check_unsafe_exec(bprm);
1515         if (retval < 0)
1516                 goto out_free;
1517         clear_in_exec = retval;
1518         current->in_execve = 1;
1519
1520         file = open_exec(filename);
1521         retval = PTR_ERR(file);
1522         if (IS_ERR(file))
1523                 goto out_unmark;
1524
1525         sched_exec();
1526
1527         bprm->file = file;
1528         bprm->filename = filename;
1529         bprm->interp = filename;
1530
1531         retval = bprm_mm_init(bprm);
1532         if (retval)
1533                 goto out_file;
1534
1535         bprm->argc = count(argv, MAX_ARG_STRINGS);
1536         if ((retval = bprm->argc) < 0)
1537                 goto out;
1538
1539         bprm->envc = count(envp, MAX_ARG_STRINGS);
1540         if ((retval = bprm->envc) < 0)
1541                 goto out;
1542
1543         retval = prepare_binprm(bprm);
1544         if (retval < 0)
1545                 goto out;
1546
1547         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1548         if (retval < 0)
1549                 goto out;
1550
1551         bprm->exec = bprm->p;
1552         retval = copy_strings(bprm->envc, envp, bprm);
1553         if (retval < 0)
1554                 goto out;
1555
1556         retval = copy_strings(bprm->argc, argv, bprm);
1557         if (retval < 0)
1558                 goto out;
1559
1560         retval = search_binary_handler(bprm,regs);
1561         if (retval < 0)
1562                 goto out;
1563
1564         /* execve succeeded */
1565         current->fs->in_exec = 0;
1566         current->in_execve = 0;
1567         acct_update_integrals(current);
1568         free_bprm(bprm);
1569         if (displaced)
1570                 put_files_struct(displaced);
1571         return retval;
1572
1573 out:
1574         if (bprm->mm) {
1575                 acct_arg_size(bprm, 0);
1576                 mmput(bprm->mm);
1577         }
1578
1579 out_file:
1580         if (bprm->file) {
1581                 allow_write_access(bprm->file);
1582                 fput(bprm->file);
1583         }
1584
1585 out_unmark:
1586         if (clear_in_exec)
1587                 current->fs->in_exec = 0;
1588         current->in_execve = 0;
1589
1590 out_free:
1591         free_bprm(bprm);
1592
1593 out_files:
1594         if (displaced)
1595                 reset_files_struct(displaced);
1596 out_ret:
1597         return retval;
1598 }
1599
1600 int do_execve(const char *filename,
1601         const char __user *const __user *__argv,
1602         const char __user *const __user *__envp,
1603         struct pt_regs *regs)
1604 {
1605         struct user_arg_ptr argv = { .ptr.native = __argv };
1606         struct user_arg_ptr envp = { .ptr.native = __envp };
1607         return do_execve_common(filename, argv, envp, regs);
1608 }
1609
1610 #ifdef CONFIG_COMPAT
1611 int compat_do_execve(char *filename,
1612         compat_uptr_t __user *__argv,
1613         compat_uptr_t __user *__envp,
1614         struct pt_regs *regs)
1615 {
1616         struct user_arg_ptr argv = {
1617                 .is_compat = true,
1618                 .ptr.compat = __argv,
1619         };
1620         struct user_arg_ptr envp = {
1621                 .is_compat = true,
1622                 .ptr.compat = __envp,
1623         };
1624         return do_execve_common(filename, argv, envp, regs);
1625 }
1626 #endif
1627
1628 void set_binfmt(struct linux_binfmt *new)
1629 {
1630         struct mm_struct *mm = current->mm;
1631
1632         if (mm->binfmt)
1633                 module_put(mm->binfmt->module);
1634
1635         mm->binfmt = new;
1636         if (new)
1637                 __module_get(new->module);
1638 }
1639
1640 EXPORT_SYMBOL(set_binfmt);
1641
1642 static int expand_corename(struct core_name *cn)
1643 {
1644         char *old_corename = cn->corename;
1645
1646         cn->size = CORENAME_MAX_SIZE * atomic_inc_return(&call_count);
1647         cn->corename = krealloc(old_corename, cn->size, GFP_KERNEL);
1648
1649         if (!cn->corename) {
1650                 kfree(old_corename);
1651                 return -ENOMEM;
1652         }
1653
1654         return 0;
1655 }
1656
1657 static int cn_printf(struct core_name *cn, const char *fmt, ...)
1658 {
1659         char *cur;
1660         int need;
1661         int ret;
1662         va_list arg;
1663
1664         va_start(arg, fmt);
1665         need = vsnprintf(NULL, 0, fmt, arg);
1666         va_end(arg);
1667
1668         if (likely(need < cn->size - cn->used - 1))
1669                 goto out_printf;
1670
1671         ret = expand_corename(cn);
1672         if (ret)
1673                 goto expand_fail;
1674
1675 out_printf:
1676         cur = cn->corename + cn->used;
1677         va_start(arg, fmt);
1678         vsnprintf(cur, need + 1, fmt, arg);
1679         va_end(arg);
1680         cn->used += need;
1681         return 0;
1682
1683 expand_fail:
1684         return ret;
1685 }
1686
1687 static void cn_escape(char *str)
1688 {
1689         for (; *str; str++)
1690                 if (*str == '/')
1691                         *str = '!';
1692 }
1693
1694 static int cn_print_exe_file(struct core_name *cn)
1695 {
1696         struct file *exe_file;
1697         char *pathbuf, *path;
1698         int ret;
1699
1700         exe_file = get_mm_exe_file(current->mm);
1701         if (!exe_file) {
1702                 char *commstart = cn->corename + cn->used;
1703                 ret = cn_printf(cn, "%s (path unknown)", current->comm);
1704                 cn_escape(commstart);
1705                 return ret;
1706         }
1707
1708         pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY);
1709         if (!pathbuf) {
1710                 ret = -ENOMEM;
1711                 goto put_exe_file;
1712         }
1713
1714         path = d_path(&exe_file->f_path, pathbuf, PATH_MAX);
1715         if (IS_ERR(path)) {
1716                 ret = PTR_ERR(path);
1717                 goto free_buf;
1718         }
1719
1720         cn_escape(path);
1721
1722         ret = cn_printf(cn, "%s", path);
1723
1724 free_buf:
1725         kfree(pathbuf);
1726 put_exe_file:
1727         fput(exe_file);
1728         return ret;
1729 }
1730
1731 /* format_corename will inspect the pattern parameter, and output a
1732  * name into corename, which must have space for at least
1733  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
1734  */
1735 static int format_corename(struct core_name *cn, long signr)
1736 {
1737         const struct cred *cred = current_cred();
1738         const char *pat_ptr = core_pattern;
1739         int ispipe = (*pat_ptr == '|');
1740         int pid_in_pattern = 0;
1741         int err = 0;
1742
1743         cn->size = CORENAME_MAX_SIZE * atomic_read(&call_count);
1744         cn->corename = kmalloc(cn->size, GFP_KERNEL);
1745         cn->used = 0;
1746
1747         if (!cn->corename)
1748                 return -ENOMEM;
1749
1750         /* Repeat as long as we have more pattern to process and more output
1751            space */
1752         while (*pat_ptr) {
1753                 if (*pat_ptr != '%') {
1754                         if (*pat_ptr == 0)
1755                                 goto out;
1756                         err = cn_printf(cn, "%c", *pat_ptr++);
1757                 } else {
1758                         switch (*++pat_ptr) {
1759                         /* single % at the end, drop that */
1760                         case 0:
1761                                 goto out;
1762                         /* Double percent, output one percent */
1763                         case '%':
1764                                 err = cn_printf(cn, "%c", '%');
1765                                 break;
1766                         /* pid */
1767                         case 'p':
1768                                 pid_in_pattern = 1;
1769                                 err = cn_printf(cn, "%d",
1770                                               task_tgid_vnr(current));
1771                                 break;
1772                         /* uid */
1773                         case 'u':
1774                                 err = cn_printf(cn, "%d", cred->uid);
1775                                 break;
1776                         /* gid */
1777                         case 'g':
1778                                 err = cn_printf(cn, "%d", cred->gid);
1779                                 break;
1780                         /* signal that caused the coredump */
1781                         case 's':
1782                                 err = cn_printf(cn, "%ld", signr);
1783                                 break;
1784                         /* UNIX time of coredump */
1785                         case 't': {
1786                                 struct timeval tv;
1787                                 do_gettimeofday(&tv);
1788                                 err = cn_printf(cn, "%lu", tv.tv_sec);
1789                                 break;
1790                         }
1791                         /* hostname */
1792                         case 'h': {
1793                                 char *namestart = cn->corename + cn->used;
1794                                 down_read(&uts_sem);
1795                                 err = cn_printf(cn, "%s",
1796                                               utsname()->nodename);
1797                                 up_read(&uts_sem);
1798                                 cn_escape(namestart);
1799                                 break;
1800                         }
1801                         /* executable */
1802                         case 'e': {
1803                                 char *commstart = cn->corename + cn->used;
1804                                 err = cn_printf(cn, "%s", current->comm);
1805                                 cn_escape(commstart);
1806                                 break;
1807                         }
1808                         case 'E':
1809                                 err = cn_print_exe_file(cn);
1810                                 break;
1811                         /* core limit size */
1812                         case 'c':
1813                                 err = cn_printf(cn, "%lu",
1814                                               rlimit(RLIMIT_CORE));
1815                                 break;
1816                         default:
1817                                 break;
1818                         }
1819                         ++pat_ptr;
1820                 }
1821
1822                 if (err)
1823                         return err;
1824         }
1825
1826         /* Backward compatibility with core_uses_pid:
1827          *
1828          * If core_pattern does not include a %p (as is the default)
1829          * and core_uses_pid is set, then .%pid will be appended to
1830          * the filename. Do not do this for piped commands. */
1831         if (!ispipe && !pid_in_pattern && core_uses_pid) {
1832                 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
1833                 if (err)
1834                         return err;
1835         }
1836 out:
1837         return ispipe;
1838 }
1839
1840 static int zap_process(struct task_struct *start, int exit_code)
1841 {
1842         struct task_struct *t;
1843         int nr = 0;
1844
1845         start->signal->flags = SIGNAL_GROUP_EXIT;
1846         start->signal->group_exit_code = exit_code;
1847         start->signal->group_stop_count = 0;
1848
1849         t = start;
1850         do {
1851                 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
1852                 if (t != current && t->mm) {
1853                         sigaddset(&t->pending.signal, SIGKILL);
1854                         signal_wake_up(t, 1);
1855                         nr++;
1856                 }
1857         } while_each_thread(start, t);
1858
1859         return nr;
1860 }
1861
1862 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
1863                                 struct core_state *core_state, int exit_code)
1864 {
1865         struct task_struct *g, *p;
1866         unsigned long flags;
1867         int nr = -EAGAIN;
1868
1869         spin_lock_irq(&tsk->sighand->siglock);
1870         if (!signal_group_exit(tsk->signal)) {
1871                 mm->core_state = core_state;
1872                 nr = zap_process(tsk, exit_code);
1873         }
1874         spin_unlock_irq(&tsk->sighand->siglock);
1875         if (unlikely(nr < 0))
1876                 return nr;
1877
1878         if (atomic_read(&mm->mm_users) == nr + 1)
1879                 goto done;
1880         /*
1881          * We should find and kill all tasks which use this mm, and we should
1882          * count them correctly into ->nr_threads. We don't take tasklist
1883          * lock, but this is safe wrt:
1884          *
1885          * fork:
1886          *      None of sub-threads can fork after zap_process(leader). All
1887          *      processes which were created before this point should be
1888          *      visible to zap_threads() because copy_process() adds the new
1889          *      process to the tail of init_task.tasks list, and lock/unlock
1890          *      of ->siglock provides a memory barrier.
1891          *
1892          * do_exit:
1893          *      The caller holds mm->mmap_sem. This means that the task which
1894          *      uses this mm can't pass exit_mm(), so it can't exit or clear
1895          *      its ->mm.
1896          *
1897          * de_thread:
1898          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
1899          *      we must see either old or new leader, this does not matter.
1900          *      However, it can change p->sighand, so lock_task_sighand(p)
1901          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
1902          *      it can't fail.
1903          *
1904          *      Note also that "g" can be the old leader with ->mm == NULL
1905          *      and already unhashed and thus removed from ->thread_group.
1906          *      This is OK, __unhash_process()->list_del_rcu() does not
1907          *      clear the ->next pointer, we will find the new leader via
1908          *      next_thread().
1909          */
1910         rcu_read_lock();
1911         for_each_process(g) {
1912                 if (g == tsk->group_leader)
1913                         continue;
1914                 if (g->flags & PF_KTHREAD)
1915                         continue;
1916                 p = g;
1917                 do {
1918                         if (p->mm) {
1919                                 if (unlikely(p->mm == mm)) {
1920                                         lock_task_sighand(p, &flags);
1921                                         nr += zap_process(p, exit_code);
1922                                         unlock_task_sighand(p, &flags);
1923                                 }
1924                                 break;
1925                         }
1926                 } while_each_thread(g, p);
1927         }
1928         rcu_read_unlock();
1929 done:
1930         atomic_set(&core_state->nr_threads, nr);
1931         return nr;
1932 }
1933
1934 static int coredump_wait(int exit_code, struct core_state *core_state)
1935 {
1936         struct task_struct *tsk = current;
1937         struct mm_struct *mm = tsk->mm;
1938         int core_waiters = -EBUSY;
1939
1940         init_completion(&core_state->startup);
1941         core_state->dumper.task = tsk;
1942         core_state->dumper.next = NULL;
1943
1944         down_write(&mm->mmap_sem);
1945         if (!mm->core_state)
1946                 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
1947         up_write(&mm->mmap_sem);
1948
1949         if (core_waiters > 0)
1950                 wait_for_completion(&core_state->startup);
1951
1952         return core_waiters;
1953 }
1954
1955 static void coredump_finish(struct mm_struct *mm)
1956 {
1957         struct core_thread *curr, *next;
1958         struct task_struct *task;
1959
1960         next = mm->core_state->dumper.next;
1961         while ((curr = next) != NULL) {
1962                 next = curr->next;
1963                 task = curr->task;
1964                 /*
1965                  * see exit_mm(), curr->task must not see
1966                  * ->task == NULL before we read ->next.
1967                  */
1968                 smp_mb();
1969                 curr->task = NULL;
1970                 wake_up_process(task);
1971         }
1972
1973         mm->core_state = NULL;
1974 }
1975
1976 /*
1977  * set_dumpable converts traditional three-value dumpable to two flags and
1978  * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
1979  * these bits are not changed atomically.  So get_dumpable can observe the
1980  * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
1981  * return either old dumpable or new one by paying attention to the order of
1982  * modifying the bits.
1983  *
1984  * dumpable |   mm->flags (binary)
1985  * old  new | initial interim  final
1986  * ---------+-----------------------
1987  *  0    1  |   00      01      01
1988  *  0    2  |   00      10(*)   11
1989  *  1    0  |   01      00      00
1990  *  1    2  |   01      11      11
1991  *  2    0  |   11      10(*)   00
1992  *  2    1  |   11      11      01
1993  *
1994  * (*) get_dumpable regards interim value of 10 as 11.
1995  */
1996 void set_dumpable(struct mm_struct *mm, int value)
1997 {
1998         switch (value) {
1999         case 0:
2000                 clear_bit(MMF_DUMPABLE, &mm->flags);
2001                 smp_wmb();
2002                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
2003                 break;
2004         case 1:
2005                 set_bit(MMF_DUMPABLE, &mm->flags);
2006                 smp_wmb();
2007                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
2008                 break;
2009         case 2:
2010                 set_bit(MMF_DUMP_SECURELY, &mm->flags);
2011                 smp_wmb();
2012                 set_bit(MMF_DUMPABLE, &mm->flags);
2013                 break;
2014         }
2015 }
2016
2017 static int __get_dumpable(unsigned long mm_flags)
2018 {
2019         int ret;
2020
2021         ret = mm_flags & MMF_DUMPABLE_MASK;
2022         return (ret >= 2) ? 2 : ret;
2023 }
2024
2025 int get_dumpable(struct mm_struct *mm)
2026 {
2027         return __get_dumpable(mm->flags);
2028 }
2029
2030 static void wait_for_dump_helpers(struct file *file)
2031 {
2032         struct pipe_inode_info *pipe;
2033
2034         pipe = file->f_path.dentry->d_inode->i_pipe;
2035
2036         pipe_lock(pipe);
2037         pipe->readers++;
2038         pipe->writers--;
2039
2040         while ((pipe->readers > 1) && (!signal_pending(current))) {
2041                 wake_up_interruptible_sync(&pipe->wait);
2042                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
2043                 pipe_wait(pipe);
2044         }
2045
2046         pipe->readers--;
2047         pipe->writers++;
2048         pipe_unlock(pipe);
2049
2050 }
2051
2052
2053 /*
2054  * umh_pipe_setup
2055  * helper function to customize the process used
2056  * to collect the core in userspace.  Specifically
2057  * it sets up a pipe and installs it as fd 0 (stdin)
2058  * for the process.  Returns 0 on success, or
2059  * PTR_ERR on failure.
2060  * Note that it also sets the core limit to 1.  This
2061  * is a special value that we use to trap recursive
2062  * core dumps
2063  */
2064 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
2065 {
2066         struct file *rp, *wp;
2067         struct fdtable *fdt;
2068         struct coredump_params *cp = (struct coredump_params *)info->data;
2069         struct files_struct *cf = current->files;
2070
2071         wp = create_write_pipe(0);
2072         if (IS_ERR(wp))
2073                 return PTR_ERR(wp);
2074
2075         rp = create_read_pipe(wp, 0);
2076         if (IS_ERR(rp)) {
2077                 free_write_pipe(wp);
2078                 return PTR_ERR(rp);
2079         }
2080
2081         cp->file = wp;
2082
2083         sys_close(0);
2084         fd_install(0, rp);
2085         spin_lock(&cf->file_lock);
2086         fdt = files_fdtable(cf);
2087         __set_open_fd(0, fdt);
2088         __clear_close_on_exec(0, fdt);
2089         spin_unlock(&cf->file_lock);
2090
2091         /* and disallow core files too */
2092         current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
2093
2094         return 0;
2095 }
2096
2097 void do_coredump(long signr, int exit_code, struct pt_regs *regs)
2098 {
2099         struct core_state core_state;
2100         struct core_name cn;
2101         struct mm_struct *mm = current->mm;
2102         struct linux_binfmt * binfmt;
2103         const struct cred *old_cred;
2104         struct cred *cred;
2105         int retval = 0;
2106         int flag = 0;
2107         int ispipe;
2108         static atomic_t core_dump_count = ATOMIC_INIT(0);
2109         struct coredump_params cprm = {
2110                 .signr = signr,
2111                 .regs = regs,
2112                 .limit = rlimit(RLIMIT_CORE),
2113                 /*
2114                  * We must use the same mm->flags while dumping core to avoid
2115                  * inconsistency of bit flags, since this flag is not protected
2116                  * by any locks.
2117                  */
2118                 .mm_flags = mm->flags,
2119         };
2120
2121         audit_core_dumps(signr);
2122
2123         binfmt = mm->binfmt;
2124         if (!binfmt || !binfmt->core_dump)
2125                 goto fail;
2126         if (!__get_dumpable(cprm.mm_flags))
2127                 goto fail;
2128
2129         cred = prepare_creds();
2130         if (!cred)
2131                 goto fail;
2132         /*
2133          *      We cannot trust fsuid as being the "true" uid of the
2134          *      process nor do we know its entire history. We only know it
2135          *      was tainted so we dump it as root in mode 2.
2136          */
2137         if (__get_dumpable(cprm.mm_flags) == 2) {
2138                 /* Setuid core dump mode */
2139                 flag = O_EXCL;          /* Stop rewrite attacks */
2140                 cred->fsuid = 0;        /* Dump root private */
2141         }
2142
2143         retval = coredump_wait(exit_code, &core_state);
2144         if (retval < 0)
2145                 goto fail_creds;
2146
2147         old_cred = override_creds(cred);
2148
2149         /*
2150          * Clear any false indication of pending signals that might
2151          * be seen by the filesystem code called to write the core file.
2152          */
2153         clear_thread_flag(TIF_SIGPENDING);
2154
2155         ispipe = format_corename(&cn, signr);
2156
2157         if (ispipe) {
2158                 int dump_count;
2159                 char **helper_argv;
2160
2161                 if (ispipe < 0) {
2162                         printk(KERN_WARNING "format_corename failed\n");
2163                         printk(KERN_WARNING "Aborting core\n");
2164                         goto fail_corename;
2165                 }
2166
2167                 if (cprm.limit == 1) {
2168                         /*
2169                          * Normally core limits are irrelevant to pipes, since
2170                          * we're not writing to the file system, but we use
2171                          * cprm.limit of 1 here as a speacial value. Any
2172                          * non-1 limit gets set to RLIM_INFINITY below, but
2173                          * a limit of 0 skips the dump.  This is a consistent
2174                          * way to catch recursive crashes.  We can still crash
2175                          * if the core_pattern binary sets RLIM_CORE =  !1
2176                          * but it runs as root, and can do lots of stupid things
2177                          * Note that we use task_tgid_vnr here to grab the pid
2178                          * of the process group leader.  That way we get the
2179                          * right pid if a thread in a multi-threaded
2180                          * core_pattern process dies.
2181                          */
2182                         printk(KERN_WARNING
2183                                 "Process %d(%s) has RLIMIT_CORE set to 1\n",
2184                                 task_tgid_vnr(current), current->comm);
2185                         printk(KERN_WARNING "Aborting core\n");
2186                         goto fail_unlock;
2187                 }
2188                 cprm.limit = RLIM_INFINITY;
2189
2190                 dump_count = atomic_inc_return(&core_dump_count);
2191                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
2192                         printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
2193                                task_tgid_vnr(current), current->comm);
2194                         printk(KERN_WARNING "Skipping core dump\n");
2195                         goto fail_dropcount;
2196                 }
2197
2198                 helper_argv = argv_split(GFP_KERNEL, cn.corename+1, NULL);
2199                 if (!helper_argv) {
2200                         printk(KERN_WARNING "%s failed to allocate memory\n",
2201                                __func__);
2202                         goto fail_dropcount;
2203                 }
2204
2205                 retval = call_usermodehelper_fns(helper_argv[0], helper_argv,
2206                                         NULL, UMH_WAIT_EXEC, umh_pipe_setup,
2207                                         NULL, &cprm);
2208                 argv_free(helper_argv);
2209                 if (retval) {
2210                         printk(KERN_INFO "Core dump to %s pipe failed\n",
2211                                cn.corename);
2212                         goto close_fail;
2213                 }
2214         } else {
2215                 struct inode *inode;
2216
2217                 if (cprm.limit < binfmt->min_coredump)
2218                         goto fail_unlock;
2219
2220                 cprm.file = filp_open(cn.corename,
2221                                  O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
2222                                  0600);
2223                 if (IS_ERR(cprm.file))
2224                         goto fail_unlock;
2225
2226                 inode = cprm.file->f_path.dentry->d_inode;
2227                 if (inode->i_nlink > 1)
2228                         goto close_fail;
2229                 if (d_unhashed(cprm.file->f_path.dentry))
2230                         goto close_fail;
2231                 /*
2232                  * AK: actually i see no reason to not allow this for named
2233                  * pipes etc, but keep the previous behaviour for now.
2234                  */
2235                 if (!S_ISREG(inode->i_mode))
2236                         goto close_fail;
2237                 /*
2238                  * Dont allow local users get cute and trick others to coredump
2239                  * into their pre-created files.
2240                  */
2241                 if (inode->i_uid != current_fsuid())
2242                         goto close_fail;
2243                 if (!cprm.file->f_op || !cprm.file->f_op->write)
2244                         goto close_fail;
2245                 if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
2246                         goto close_fail;
2247         }
2248
2249         retval = binfmt->core_dump(&cprm);
2250         if (retval)
2251                 current->signal->group_exit_code |= 0x80;
2252
2253         if (ispipe && core_pipe_limit)
2254                 wait_for_dump_helpers(cprm.file);
2255 close_fail:
2256         if (cprm.file)
2257                 filp_close(cprm.file, NULL);
2258 fail_dropcount:
2259         if (ispipe)
2260                 atomic_dec(&core_dump_count);
2261 fail_unlock:
2262         kfree(cn.corename);
2263 fail_corename:
2264         coredump_finish(mm);
2265         revert_creds(old_cred);
2266 fail_creds:
2267         put_cred(cred);
2268 fail:
2269         return;
2270 }
2271
2272 /*
2273  * Core dumping helper functions.  These are the only things you should
2274  * do on a core-file: use only these functions to write out all the
2275  * necessary info.
2276  */
2277 int dump_write(struct file *file, const void *addr, int nr)
2278 {
2279         return access_ok(VERIFY_READ, addr, nr) && file->f_op->write(file, addr, nr, &file->f_pos) == nr;
2280 }
2281 EXPORT_SYMBOL(dump_write);
2282
2283 int dump_seek(struct file *file, loff_t off)
2284 {
2285         int ret = 1;
2286
2287         if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
2288                 if (file->f_op->llseek(file, off, SEEK_CUR) < 0)
2289                         return 0;
2290         } else {
2291                 char *buf = (char *)get_zeroed_page(GFP_KERNEL);
2292
2293                 if (!buf)
2294                         return 0;
2295                 while (off > 0) {
2296                         unsigned long n = off;
2297
2298                         if (n > PAGE_SIZE)
2299                                 n = PAGE_SIZE;
2300                         if (!dump_write(file, buf, n)) {
2301                                 ret = 0;
2302                                 break;
2303                         }
2304                         off -= n;
2305                 }
2306                 free_page((unsigned long)buf);
2307         }
2308         return ret;
2309 }
2310 EXPORT_SYMBOL(dump_seek);