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TOMOYO Linux Cross Reference
Linux/fs/exec.c

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

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