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Linux/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/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 <linux/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         unsigned int gup_flags = FOLL_FORCE;
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 
204         if (write)
205                 gup_flags |= FOLL_WRITE;
206 
207         /*
208          * We are doing an exec().  'current' is the process
209          * doing the exec and bprm->mm is the new process's mm.
210          */
211         ret = get_user_pages_remote(current, bprm->mm, pos, 1, gup_flags,
212                         &page, NULL, NULL);
213         if (ret <= 0)
214                 return NULL;
215 
216         if (write) {
217                 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
218                 struct rlimit *rlim;
219 
220                 acct_arg_size(bprm, size / PAGE_SIZE);
221 
222                 /*
223                  * We've historically supported up to 32 pages (ARG_MAX)
224                  * of argument strings even with small stacks
225                  */
226                 if (size <= ARG_MAX)
227                         return page;
228 
229                 /*
230                  * Limit to 1/4-th the stack size for the argv+env strings.
231                  * This ensures that:
232                  *  - the remaining binfmt code will not run out of stack space,
233                  *  - the program will have a reasonable amount of stack left
234                  *    to work from.
235                  */
236                 rlim = current->signal->rlim;
237                 if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) {
238                         put_page(page);
239                         return NULL;
240                 }
241         }
242 
243         return page;
244 }
245 
246 static void put_arg_page(struct page *page)
247 {
248         put_page(page);
249 }
250 
251 static void free_arg_pages(struct linux_binprm *bprm)
252 {
253 }
254 
255 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
256                 struct page *page)
257 {
258         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
259 }
260 
261 static int __bprm_mm_init(struct linux_binprm *bprm)
262 {
263         int err;
264         struct vm_area_struct *vma = NULL;
265         struct mm_struct *mm = bprm->mm;
266 
267         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
268         if (!vma)
269                 return -ENOMEM;
270 
271         if (down_write_killable(&mm->mmap_sem)) {
272                 err = -EINTR;
273                 goto err_free;
274         }
275         vma->vm_mm = mm;
276 
277         /*
278          * Place the stack at the largest stack address the architecture
279          * supports. Later, we'll move this to an appropriate place. We don't
280          * use STACK_TOP because that can depend on attributes which aren't
281          * configured yet.
282          */
283         BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
284         vma->vm_end = STACK_TOP_MAX;
285         vma->vm_start = vma->vm_end - PAGE_SIZE;
286         vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
287         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
288         INIT_LIST_HEAD(&vma->anon_vma_chain);
289 
290         err = insert_vm_struct(mm, vma);
291         if (err)
292                 goto err;
293 
294         mm->stack_vm = mm->total_vm = 1;
295         arch_bprm_mm_init(mm, vma);
296         up_write(&mm->mmap_sem);
297         bprm->p = vma->vm_end - sizeof(void *);
298         return 0;
299 err:
300         up_write(&mm->mmap_sem);
301 err_free:
302         bprm->vma = NULL;
303         kmem_cache_free(vm_area_cachep, vma);
304         return err;
305 }
306 
307 static bool valid_arg_len(struct linux_binprm *bprm, long len)
308 {
309         return len <= MAX_ARG_STRLEN;
310 }
311 
312 #else
313 
314 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
315 {
316 }
317 
318 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
319                 int write)
320 {
321         struct page *page;
322 
323         page = bprm->page[pos / PAGE_SIZE];
324         if (!page && write) {
325                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
326                 if (!page)
327                         return NULL;
328                 bprm->page[pos / PAGE_SIZE] = page;
329         }
330 
331         return page;
332 }
333 
334 static void put_arg_page(struct page *page)
335 {
336 }
337 
338 static void free_arg_page(struct linux_binprm *bprm, int i)
339 {
340         if (bprm->page[i]) {
341                 __free_page(bprm->page[i]);
342                 bprm->page[i] = NULL;
343         }
344 }
345 
346 static void free_arg_pages(struct linux_binprm *bprm)
347 {
348         int i;
349 
350         for (i = 0; i < MAX_ARG_PAGES; i++)
351                 free_arg_page(bprm, i);
352 }
353 
354 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
355                 struct page *page)
356 {
357 }
358 
359 static int __bprm_mm_init(struct linux_binprm *bprm)
360 {
361         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
362         return 0;
363 }
364 
365 static bool valid_arg_len(struct linux_binprm *bprm, long len)
366 {
367         return len <= bprm->p;
368 }
369 
370 #endif /* CONFIG_MMU */
371 
372 /*
373  * Create a new mm_struct and populate it with a temporary stack
374  * vm_area_struct.  We don't have enough context at this point to set the stack
375  * flags, permissions, and offset, so we use temporary values.  We'll update
376  * them later in setup_arg_pages().
377  */
378 static int bprm_mm_init(struct linux_binprm *bprm)
379 {
380         int err;
381         struct mm_struct *mm = NULL;
382 
383         bprm->mm = mm = mm_alloc();
384         err = -ENOMEM;
385         if (!mm)
386                 goto err;
387 
388         err = __bprm_mm_init(bprm);
389         if (err)
390                 goto err;
391 
392         return 0;
393 
394 err:
395         if (mm) {
396                 bprm->mm = NULL;
397                 mmdrop(mm);
398         }
399 
400         return err;
401 }
402 
403 struct user_arg_ptr {
404 #ifdef CONFIG_COMPAT
405         bool is_compat;
406 #endif
407         union {
408                 const char __user *const __user *native;
409 #ifdef CONFIG_COMPAT
410                 const compat_uptr_t __user *compat;
411 #endif
412         } ptr;
413 };
414 
415 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
416 {
417         const char __user *native;
418 
419 #ifdef CONFIG_COMPAT
420         if (unlikely(argv.is_compat)) {
421                 compat_uptr_t compat;
422 
423                 if (get_user(compat, argv.ptr.compat + nr))
424                         return ERR_PTR(-EFAULT);
425 
426                 return compat_ptr(compat);
427         }
428 #endif
429 
430         if (get_user(native, argv.ptr.native + nr))
431                 return ERR_PTR(-EFAULT);
432 
433         return native;
434 }
435 
436 /*
437  * count() counts the number of strings in array ARGV.
438  */
439 static int count(struct user_arg_ptr argv, int max)
440 {
441         int i = 0;
442 
443         if (argv.ptr.native != NULL) {
444                 for (;;) {
445                         const char __user *p = get_user_arg_ptr(argv, i);
446 
447                         if (!p)
448                                 break;
449 
450                         if (IS_ERR(p))
451                                 return -EFAULT;
452 
453                         if (i >= max)
454                                 return -E2BIG;
455                         ++i;
456 
457                         if (fatal_signal_pending(current))
458                                 return -ERESTARTNOHAND;
459                         cond_resched();
460                 }
461         }
462         return i;
463 }
464 
465 /*
466  * 'copy_strings()' copies argument/environment strings from the old
467  * processes's memory to the new process's stack.  The call to get_user_pages()
468  * ensures the destination page is created and not swapped out.
469  */
470 static int copy_strings(int argc, struct user_arg_ptr argv,
471                         struct linux_binprm *bprm)
472 {
473         struct page *kmapped_page = NULL;
474         char *kaddr = NULL;
475         unsigned long kpos = 0;
476         int ret;
477 
478         while (argc-- > 0) {
479                 const char __user *str;
480                 int len;
481                 unsigned long pos;
482 
483                 ret = -EFAULT;
484                 str = get_user_arg_ptr(argv, argc);
485                 if (IS_ERR(str))
486                         goto out;
487 
488                 len = strnlen_user(str, MAX_ARG_STRLEN);
489                 if (!len)
490                         goto out;
491 
492                 ret = -E2BIG;
493                 if (!valid_arg_len(bprm, len))
494                         goto out;
495 
496                 /* We're going to work our way backwords. */
497                 pos = bprm->p;
498                 str += len;
499                 bprm->p -= len;
500 
501                 while (len > 0) {
502                         int offset, bytes_to_copy;
503 
504                         if (fatal_signal_pending(current)) {
505                                 ret = -ERESTARTNOHAND;
506                                 goto out;
507                         }
508                         cond_resched();
509 
510                         offset = pos % PAGE_SIZE;
511                         if (offset == 0)
512                                 offset = PAGE_SIZE;
513 
514                         bytes_to_copy = offset;
515                         if (bytes_to_copy > len)
516                                 bytes_to_copy = len;
517 
518                         offset -= bytes_to_copy;
519                         pos -= bytes_to_copy;
520                         str -= bytes_to_copy;
521                         len -= bytes_to_copy;
522 
523                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
524                                 struct page *page;
525 
526                                 page = get_arg_page(bprm, pos, 1);
527                                 if (!page) {
528                                         ret = -E2BIG;
529                                         goto out;
530                                 }
531 
532                                 if (kmapped_page) {
533                                         flush_kernel_dcache_page(kmapped_page);
534                                         kunmap(kmapped_page);
535                                         put_arg_page(kmapped_page);
536                                 }
537                                 kmapped_page = page;
538                                 kaddr = kmap(kmapped_page);
539                                 kpos = pos & PAGE_MASK;
540                                 flush_arg_page(bprm, kpos, kmapped_page);
541                         }
542                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
543                                 ret = -EFAULT;
544                                 goto out;
545                         }
546                 }
547         }
548         ret = 0;
549 out:
550         if (kmapped_page) {
551                 flush_kernel_dcache_page(kmapped_page);
552                 kunmap(kmapped_page);
553                 put_arg_page(kmapped_page);
554         }
555         return ret;
556 }
557 
558 /*
559  * Like copy_strings, but get argv and its values from kernel memory.
560  */
561 int copy_strings_kernel(int argc, const char *const *__argv,
562                         struct linux_binprm *bprm)
563 {
564         int r;
565         mm_segment_t oldfs = get_fs();
566         struct user_arg_ptr argv = {
567                 .ptr.native = (const char __user *const  __user *)__argv,
568         };
569 
570         set_fs(KERNEL_DS);
571         r = copy_strings(argc, argv, bprm);
572         set_fs(oldfs);
573 
574         return r;
575 }
576 EXPORT_SYMBOL(copy_strings_kernel);
577 
578 #ifdef CONFIG_MMU
579 
580 /*
581  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
582  * the binfmt code determines where the new stack should reside, we shift it to
583  * its final location.  The process proceeds as follows:
584  *
585  * 1) Use shift to calculate the new vma endpoints.
586  * 2) Extend vma to cover both the old and new ranges.  This ensures the
587  *    arguments passed to subsequent functions are consistent.
588  * 3) Move vma's page tables to the new range.
589  * 4) Free up any cleared pgd range.
590  * 5) Shrink the vma to cover only the new range.
591  */
592 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
593 {
594         struct mm_struct *mm = vma->vm_mm;
595         unsigned long old_start = vma->vm_start;
596         unsigned long old_end = vma->vm_end;
597         unsigned long length = old_end - old_start;
598         unsigned long new_start = old_start - shift;
599         unsigned long new_end = old_end - shift;
600         struct mmu_gather tlb;
601 
602         BUG_ON(new_start > new_end);
603 
604         /*
605          * ensure there are no vmas between where we want to go
606          * and where we are
607          */
608         if (vma != find_vma(mm, new_start))
609                 return -EFAULT;
610 
611         /*
612          * cover the whole range: [new_start, old_end)
613          */
614         if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
615                 return -ENOMEM;
616 
617         /*
618          * move the page tables downwards, on failure we rely on
619          * process cleanup to remove whatever mess we made.
620          */
621         if (length != move_page_tables(vma, old_start,
622                                        vma, new_start, length, false))
623                 return -ENOMEM;
624 
625         lru_add_drain();
626         tlb_gather_mmu(&tlb, mm, old_start, old_end);
627         if (new_end > old_start) {
628                 /*
629                  * when the old and new regions overlap clear from new_end.
630                  */
631                 free_pgd_range(&tlb, new_end, old_end, new_end,
632                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
633         } else {
634                 /*
635                  * otherwise, clean from old_start; this is done to not touch
636                  * the address space in [new_end, old_start) some architectures
637                  * have constraints on va-space that make this illegal (IA64) -
638                  * for the others its just a little faster.
639                  */
640                 free_pgd_range(&tlb, old_start, old_end, new_end,
641                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
642         }
643         tlb_finish_mmu(&tlb, old_start, old_end);
644 
645         /*
646          * Shrink the vma to just the new range.  Always succeeds.
647          */
648         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
649 
650         return 0;
651 }
652 
653 /*
654  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
655  * the stack is optionally relocated, and some extra space is added.
656  */
657 int setup_arg_pages(struct linux_binprm *bprm,
658                     unsigned long stack_top,
659                     int executable_stack)
660 {
661         unsigned long ret;
662         unsigned long stack_shift;
663         struct mm_struct *mm = current->mm;
664         struct vm_area_struct *vma = bprm->vma;
665         struct vm_area_struct *prev = NULL;
666         unsigned long vm_flags;
667         unsigned long stack_base;
668         unsigned long stack_size;
669         unsigned long stack_expand;
670         unsigned long rlim_stack;
671 
672 #ifdef CONFIG_STACK_GROWSUP
673         /* Limit stack size */
674         stack_base = rlimit_max(RLIMIT_STACK);
675         if (stack_base > STACK_SIZE_MAX)
676                 stack_base = STACK_SIZE_MAX;
677 
678         /* Add space for stack randomization. */
679         stack_base += (STACK_RND_MASK << PAGE_SHIFT);
680 
681         /* Make sure we didn't let the argument array grow too large. */
682         if (vma->vm_end - vma->vm_start > stack_base)
683                 return -ENOMEM;
684 
685         stack_base = PAGE_ALIGN(stack_top - stack_base);
686 
687         stack_shift = vma->vm_start - stack_base;
688         mm->arg_start = bprm->p - stack_shift;
689         bprm->p = vma->vm_end - stack_shift;
690 #else
691         stack_top = arch_align_stack(stack_top);
692         stack_top = PAGE_ALIGN(stack_top);
693 
694         if (unlikely(stack_top < mmap_min_addr) ||
695             unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
696                 return -ENOMEM;
697 
698         stack_shift = vma->vm_end - stack_top;
699 
700         bprm->p -= stack_shift;
701         mm->arg_start = bprm->p;
702 #endif
703 
704         if (bprm->loader)
705                 bprm->loader -= stack_shift;
706         bprm->exec -= stack_shift;
707 
708         if (down_write_killable(&mm->mmap_sem))
709                 return -EINTR;
710 
711         vm_flags = VM_STACK_FLAGS;
712 
713         /*
714          * Adjust stack execute permissions; explicitly enable for
715          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
716          * (arch default) otherwise.
717          */
718         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
719                 vm_flags |= VM_EXEC;
720         else if (executable_stack == EXSTACK_DISABLE_X)
721                 vm_flags &= ~VM_EXEC;
722         vm_flags |= mm->def_flags;
723         vm_flags |= VM_STACK_INCOMPLETE_SETUP;
724 
725         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
726                         vm_flags);
727         if (ret)
728                 goto out_unlock;
729         BUG_ON(prev != vma);
730 
731         /* Move stack pages down in memory. */
732         if (stack_shift) {
733                 ret = shift_arg_pages(vma, stack_shift);
734                 if (ret)
735                         goto out_unlock;
736         }
737 
738         /* mprotect_fixup is overkill to remove the temporary stack flags */
739         vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
740 
741         stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
742         stack_size = vma->vm_end - vma->vm_start;
743         /*
744          * Align this down to a page boundary as expand_stack
745          * will align it up.
746          */
747         rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
748 #ifdef CONFIG_STACK_GROWSUP
749         if (stack_size + stack_expand > rlim_stack)
750                 stack_base = vma->vm_start + rlim_stack;
751         else
752                 stack_base = vma->vm_end + stack_expand;
753 #else
754         if (stack_size + stack_expand > rlim_stack)
755                 stack_base = vma->vm_end - rlim_stack;
756         else
757                 stack_base = vma->vm_start - stack_expand;
758 #endif
759         current->mm->start_stack = bprm->p;
760         ret = expand_stack(vma, stack_base);
761         if (ret)
762                 ret = -EFAULT;
763 
764 out_unlock:
765         up_write(&mm->mmap_sem);
766         return ret;
767 }
768 EXPORT_SYMBOL(setup_arg_pages);
769 
770 #else
771 
772 /*
773  * Transfer the program arguments and environment from the holding pages
774  * onto the stack. The provided stack pointer is adjusted accordingly.
775  */
776 int transfer_args_to_stack(struct linux_binprm *bprm,
777                            unsigned long *sp_location)
778 {
779         unsigned long index, stop, sp;
780         int ret = 0;
781 
782         stop = bprm->p >> PAGE_SHIFT;
783         sp = *sp_location;
784 
785         for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
786                 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
787                 char *src = kmap(bprm->page[index]) + offset;
788                 sp -= PAGE_SIZE - offset;
789                 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
790                         ret = -EFAULT;
791                 kunmap(bprm->page[index]);
792                 if (ret)
793                         goto out;
794         }
795 
796         *sp_location = sp;
797 
798 out:
799         return ret;
800 }
801 EXPORT_SYMBOL(transfer_args_to_stack);
802 
803 #endif /* CONFIG_MMU */
804 
805 static struct file *do_open_execat(int fd, struct filename *name, int flags)
806 {
807         struct file *file;
808         int err;
809         struct open_flags open_exec_flags = {
810                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
811                 .acc_mode = MAY_EXEC,
812                 .intent = LOOKUP_OPEN,
813                 .lookup_flags = LOOKUP_FOLLOW,
814         };
815 
816         if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
817                 return ERR_PTR(-EINVAL);
818         if (flags & AT_SYMLINK_NOFOLLOW)
819                 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
820         if (flags & AT_EMPTY_PATH)
821                 open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
822 
823         file = do_filp_open(fd, name, &open_exec_flags);
824         if (IS_ERR(file))
825                 goto out;
826 
827         err = -EACCES;
828         if (!S_ISREG(file_inode(file)->i_mode))
829                 goto exit;
830 
831         if (path_noexec(&file->f_path))
832                 goto exit;
833 
834         err = deny_write_access(file);
835         if (err)
836                 goto exit;
837 
838         if (name->name[0] != '\0')
839                 fsnotify_open(file);
840 
841 out:
842         return file;
843 
844 exit:
845         fput(file);
846         return ERR_PTR(err);
847 }
848 
849 struct file *open_exec(const char *name)
850 {
851         struct filename *filename = getname_kernel(name);
852         struct file *f = ERR_CAST(filename);
853 
854         if (!IS_ERR(filename)) {
855                 f = do_open_execat(AT_FDCWD, filename, 0);
856                 putname(filename);
857         }
858         return f;
859 }
860 EXPORT_SYMBOL(open_exec);
861 
862 int kernel_read(struct file *file, loff_t offset,
863                 char *addr, unsigned long count)
864 {
865         mm_segment_t old_fs;
866         loff_t pos = offset;
867         int result;
868 
869         old_fs = get_fs();
870         set_fs(get_ds());
871         /* The cast to a user pointer is valid due to the set_fs() */
872         result = vfs_read(file, (void __user *)addr, count, &pos);
873         set_fs(old_fs);
874         return result;
875 }
876 
877 EXPORT_SYMBOL(kernel_read);
878 
879 int kernel_read_file(struct file *file, void **buf, loff_t *size,
880                      loff_t max_size, enum kernel_read_file_id id)
881 {
882         loff_t i_size, pos;
883         ssize_t bytes = 0;
884         int ret;
885 
886         if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
887                 return -EINVAL;
888 
889         ret = security_kernel_read_file(file, id);
890         if (ret)
891                 return ret;
892 
893         ret = deny_write_access(file);
894         if (ret)
895                 return ret;
896 
897         i_size = i_size_read(file_inode(file));
898         if (max_size > 0 && i_size > max_size) {
899                 ret = -EFBIG;
900                 goto out;
901         }
902         if (i_size <= 0) {
903                 ret = -EINVAL;
904                 goto out;
905         }
906 
907         if (id != READING_FIRMWARE_PREALLOC_BUFFER)
908                 *buf = vmalloc(i_size);
909         if (!*buf) {
910                 ret = -ENOMEM;
911                 goto out;
912         }
913 
914         pos = 0;
915         while (pos < i_size) {
916                 bytes = kernel_read(file, pos, (char *)(*buf) + pos,
917                                     i_size - pos);
918                 if (bytes < 0) {
919                         ret = bytes;
920                         goto out;
921                 }
922 
923                 if (bytes == 0)
924                         break;
925                 pos += bytes;
926         }
927 
928         if (pos != i_size) {
929                 ret = -EIO;
930                 goto out_free;
931         }
932 
933         ret = security_kernel_post_read_file(file, *buf, i_size, id);
934         if (!ret)
935                 *size = pos;
936 
937 out_free:
938         if (ret < 0) {
939                 if (id != READING_FIRMWARE_PREALLOC_BUFFER) {
940                         vfree(*buf);
941                         *buf = NULL;
942                 }
943         }
944 
945 out:
946         allow_write_access(file);
947         return ret;
948 }
949 EXPORT_SYMBOL_GPL(kernel_read_file);
950 
951 int kernel_read_file_from_path(char *path, void **buf, loff_t *size,
952                                loff_t max_size, enum kernel_read_file_id id)
953 {
954         struct file *file;
955         int ret;
956 
957         if (!path || !*path)
958                 return -EINVAL;
959 
960         file = filp_open(path, O_RDONLY, 0);
961         if (IS_ERR(file))
962                 return PTR_ERR(file);
963 
964         ret = kernel_read_file(file, buf, size, max_size, id);
965         fput(file);
966         return ret;
967 }
968 EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
969 
970 int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
971                              enum kernel_read_file_id id)
972 {
973         struct fd f = fdget(fd);
974         int ret = -EBADF;
975 
976         if (!f.file)
977                 goto out;
978 
979         ret = kernel_read_file(f.file, buf, size, max_size, id);
980 out:
981         fdput(f);
982         return ret;
983 }
984 EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);
985 
986 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
987 {
988         ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
989         if (res > 0)
990                 flush_icache_range(addr, addr + len);
991         return res;
992 }
993 EXPORT_SYMBOL(read_code);
994 
995 static int exec_mmap(struct mm_struct *mm)
996 {
997         struct task_struct *tsk;
998         struct mm_struct *old_mm, *active_mm;
999 
1000         /* Notify parent that we're no longer interested in the old VM */
1001         tsk = current;
1002         old_mm = current->mm;
1003         mm_release(tsk, old_mm);
1004 
1005         if (old_mm) {
1006                 sync_mm_rss(old_mm);
1007                 /*
1008                  * Make sure that if there is a core dump in progress
1009                  * for the old mm, we get out and die instead of going
1010                  * through with the exec.  We must hold mmap_sem around
1011                  * checking core_state and changing tsk->mm.
1012                  */
1013                 down_read(&old_mm->mmap_sem);
1014                 if (unlikely(old_mm->core_state)) {
1015                         up_read(&old_mm->mmap_sem);
1016                         return -EINTR;
1017                 }
1018         }
1019         task_lock(tsk);
1020         active_mm = tsk->active_mm;
1021         tsk->mm = mm;
1022         tsk->active_mm = mm;
1023         activate_mm(active_mm, mm);
1024         tsk->mm->vmacache_seqnum = 0;
1025         vmacache_flush(tsk);
1026         task_unlock(tsk);
1027         if (old_mm) {
1028                 up_read(&old_mm->mmap_sem);
1029                 BUG_ON(active_mm != old_mm);
1030                 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
1031                 mm_update_next_owner(old_mm);
1032                 mmput(old_mm);
1033                 return 0;
1034         }
1035         mmdrop(active_mm);
1036         return 0;
1037 }
1038 
1039 /*
1040  * This function makes sure the current process has its own signal table,
1041  * so that flush_signal_handlers can later reset the handlers without
1042  * disturbing other processes.  (Other processes might share the signal
1043  * table via the CLONE_SIGHAND option to clone().)
1044  */
1045 static int de_thread(struct task_struct *tsk)
1046 {
1047         struct signal_struct *sig = tsk->signal;
1048         struct sighand_struct *oldsighand = tsk->sighand;
1049         spinlock_t *lock = &oldsighand->siglock;
1050 
1051         if (thread_group_empty(tsk))
1052                 goto no_thread_group;
1053 
1054         /*
1055          * Kill all other threads in the thread group.
1056          */
1057         spin_lock_irq(lock);
1058         if (signal_group_exit(sig)) {
1059                 /*
1060                  * Another group action in progress, just
1061                  * return so that the signal is processed.
1062                  */
1063                 spin_unlock_irq(lock);
1064                 return -EAGAIN;
1065         }
1066 
1067         sig->group_exit_task = tsk;
1068         sig->notify_count = zap_other_threads(tsk);
1069         if (!thread_group_leader(tsk))
1070                 sig->notify_count--;
1071 
1072         while (sig->notify_count) {
1073                 __set_current_state(TASK_KILLABLE);
1074                 spin_unlock_irq(lock);
1075                 schedule();
1076                 if (unlikely(__fatal_signal_pending(tsk)))
1077                         goto killed;
1078                 spin_lock_irq(lock);
1079         }
1080         spin_unlock_irq(lock);
1081 
1082         /*
1083          * At this point all other threads have exited, all we have to
1084          * do is to wait for the thread group leader to become inactive,
1085          * and to assume its PID:
1086          */
1087         if (!thread_group_leader(tsk)) {
1088                 struct task_struct *leader = tsk->group_leader;
1089 
1090                 for (;;) {
1091                         threadgroup_change_begin(tsk);
1092                         write_lock_irq(&tasklist_lock);
1093                         /*
1094                          * Do this under tasklist_lock to ensure that
1095                          * exit_notify() can't miss ->group_exit_task
1096                          */
1097                         sig->notify_count = -1;
1098                         if (likely(leader->exit_state))
1099                                 break;
1100                         __set_current_state(TASK_KILLABLE);
1101                         write_unlock_irq(&tasklist_lock);
1102                         threadgroup_change_end(tsk);
1103                         schedule();
1104                         if (unlikely(__fatal_signal_pending(tsk)))
1105                                 goto killed;
1106                 }
1107 
1108                 /*
1109                  * The only record we have of the real-time age of a
1110                  * process, regardless of execs it's done, is start_time.
1111                  * All the past CPU time is accumulated in signal_struct
1112                  * from sister threads now dead.  But in this non-leader
1113                  * exec, nothing survives from the original leader thread,
1114                  * whose birth marks the true age of this process now.
1115                  * When we take on its identity by switching to its PID, we
1116                  * also take its birthdate (always earlier than our own).
1117                  */
1118                 tsk->start_time = leader->start_time;
1119                 tsk->real_start_time = leader->real_start_time;
1120 
1121                 BUG_ON(!same_thread_group(leader, tsk));
1122                 BUG_ON(has_group_leader_pid(tsk));
1123                 /*
1124                  * An exec() starts a new thread group with the
1125                  * TGID of the previous thread group. Rehash the
1126                  * two threads with a switched PID, and release
1127                  * the former thread group leader:
1128                  */
1129 
1130                 /* Become a process group leader with the old leader's pid.
1131                  * The old leader becomes a thread of the this thread group.
1132                  * Note: The old leader also uses this pid until release_task
1133                  *       is called.  Odd but simple and correct.
1134                  */
1135                 tsk->pid = leader->pid;
1136                 change_pid(tsk, PIDTYPE_PID, task_pid(leader));
1137                 transfer_pid(leader, tsk, PIDTYPE_PGID);
1138                 transfer_pid(leader, tsk, PIDTYPE_SID);
1139 
1140                 list_replace_rcu(&leader->tasks, &tsk->tasks);
1141                 list_replace_init(&leader->sibling, &tsk->sibling);
1142 
1143                 tsk->group_leader = tsk;
1144                 leader->group_leader = tsk;
1145 
1146                 tsk->exit_signal = SIGCHLD;
1147                 leader->exit_signal = -1;
1148 
1149                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1150                 leader->exit_state = EXIT_DEAD;
1151 
1152                 /*
1153                  * We are going to release_task()->ptrace_unlink() silently,
1154                  * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1155                  * the tracer wont't block again waiting for this thread.
1156                  */
1157                 if (unlikely(leader->ptrace))
1158                         __wake_up_parent(leader, leader->parent);
1159                 write_unlock_irq(&tasklist_lock);
1160                 threadgroup_change_end(tsk);
1161 
1162                 release_task(leader);
1163         }
1164 
1165         sig->group_exit_task = NULL;
1166         sig->notify_count = 0;
1167 
1168 no_thread_group:
1169         /* we have changed execution domain */
1170         tsk->exit_signal = SIGCHLD;
1171 
1172 #ifdef CONFIG_POSIX_TIMERS
1173         exit_itimers(sig);
1174         flush_itimer_signals();
1175 #endif
1176 
1177         if (atomic_read(&oldsighand->count) != 1) {
1178                 struct sighand_struct *newsighand;
1179                 /*
1180                  * This ->sighand is shared with the CLONE_SIGHAND
1181                  * but not CLONE_THREAD task, switch to the new one.
1182                  */
1183                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1184                 if (!newsighand)
1185                         return -ENOMEM;
1186 
1187                 atomic_set(&newsighand->count, 1);
1188                 memcpy(newsighand->action, oldsighand->action,
1189                        sizeof(newsighand->action));
1190 
1191                 write_lock_irq(&tasklist_lock);
1192                 spin_lock(&oldsighand->siglock);
1193                 rcu_assign_pointer(tsk->sighand, newsighand);
1194                 spin_unlock(&oldsighand->siglock);
1195                 write_unlock_irq(&tasklist_lock);
1196 
1197                 __cleanup_sighand(oldsighand);
1198         }
1199 
1200         BUG_ON(!thread_group_leader(tsk));
1201         return 0;
1202 
1203 killed:
1204         /* protects against exit_notify() and __exit_signal() */
1205         read_lock(&tasklist_lock);
1206         sig->group_exit_task = NULL;
1207         sig->notify_count = 0;
1208         read_unlock(&tasklist_lock);
1209         return -EAGAIN;
1210 }
1211 
1212 char *get_task_comm(char *buf, struct task_struct *tsk)
1213 {
1214         /* buf must be at least sizeof(tsk->comm) in size */
1215         task_lock(tsk);
1216         strncpy(buf, tsk->comm, sizeof(tsk->comm));
1217         task_unlock(tsk);
1218         return buf;
1219 }
1220 EXPORT_SYMBOL_GPL(get_task_comm);
1221 
1222 /*
1223  * These functions flushes out all traces of the currently running executable
1224  * so that a new one can be started
1225  */
1226 
1227 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1228 {
1229         task_lock(tsk);
1230         trace_task_rename(tsk, buf);
1231         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1232         task_unlock(tsk);
1233         perf_event_comm(tsk, exec);
1234 }
1235 
1236 int flush_old_exec(struct linux_binprm * bprm)
1237 {
1238         int retval;
1239 
1240         /*
1241          * Make sure we have a private signal table and that
1242          * we are unassociated from the previous thread group.
1243          */
1244         retval = de_thread(current);
1245         if (retval)
1246                 goto out;
1247 
1248         /*
1249          * Must be called _before_ exec_mmap() as bprm->mm is
1250          * not visibile until then. This also enables the update
1251          * to be lockless.
1252          */
1253         set_mm_exe_file(bprm->mm, bprm->file);
1254 
1255         /*
1256          * Release all of the old mmap stuff
1257          */
1258         acct_arg_size(bprm, 0);
1259         retval = exec_mmap(bprm->mm);
1260         if (retval)
1261                 goto out;
1262 
1263         bprm->mm = NULL;                /* We're using it now */
1264 
1265         set_fs(USER_DS);
1266         current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
1267                                         PF_NOFREEZE | PF_NO_SETAFFINITY);
1268         flush_thread();
1269         current->personality &= ~bprm->per_clear;
1270 
1271         /*
1272          * We have to apply CLOEXEC before we change whether the process is
1273          * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1274          * trying to access the should-be-closed file descriptors of a process
1275          * undergoing exec(2).
1276          */
1277         do_close_on_exec(current->files);
1278         return 0;
1279 
1280 out:
1281         return retval;
1282 }
1283 EXPORT_SYMBOL(flush_old_exec);
1284 
1285 void would_dump(struct linux_binprm *bprm, struct file *file)
1286 {
1287         struct inode *inode = file_inode(file);
1288         if (inode_permission(inode, MAY_READ) < 0) {
1289                 struct user_namespace *old, *user_ns;
1290                 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1291 
1292                 /* Ensure mm->user_ns contains the executable */
1293                 user_ns = old = bprm->mm->user_ns;
1294                 while ((user_ns != &init_user_ns) &&
1295                        !privileged_wrt_inode_uidgid(user_ns, inode))
1296                         user_ns = user_ns->parent;
1297 
1298                 if (old != user_ns) {
1299                         bprm->mm->user_ns = get_user_ns(user_ns);
1300                         put_user_ns(old);
1301                 }
1302         }
1303 }
1304 EXPORT_SYMBOL(would_dump);
1305 
1306 void setup_new_exec(struct linux_binprm * bprm)
1307 {
1308         arch_pick_mmap_layout(current->mm);
1309 
1310         /* This is the point of no return */
1311         current->sas_ss_sp = current->sas_ss_size = 0;
1312 
1313         if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid()))
1314                 set_dumpable(current->mm, SUID_DUMP_USER);
1315         else
1316                 set_dumpable(current->mm, suid_dumpable);
1317 
1318         perf_event_exec();
1319         __set_task_comm(current, kbasename(bprm->filename), true);
1320 
1321         /* Set the new mm task size. We have to do that late because it may
1322          * depend on TIF_32BIT which is only updated in flush_thread() on
1323          * some architectures like powerpc
1324          */
1325         current->mm->task_size = TASK_SIZE;
1326 
1327         /* install the new credentials */
1328         if (!uid_eq(bprm->cred->uid, current_euid()) ||
1329             !gid_eq(bprm->cred->gid, current_egid())) {
1330                 current->pdeath_signal = 0;
1331         } else {
1332                 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
1333                         set_dumpable(current->mm, suid_dumpable);
1334         }
1335 
1336         /* An exec changes our domain. We are no longer part of the thread
1337            group */
1338         current->self_exec_id++;
1339         flush_signal_handlers(current, 0);
1340 }
1341 EXPORT_SYMBOL(setup_new_exec);
1342 
1343 /*
1344  * Prepare credentials and lock ->cred_guard_mutex.
1345  * install_exec_creds() commits the new creds and drops the lock.
1346  * Or, if exec fails before, free_bprm() should release ->cred and
1347  * and unlock.
1348  */
1349 int prepare_bprm_creds(struct linux_binprm *bprm)
1350 {
1351         if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1352                 return -ERESTARTNOINTR;
1353 
1354         bprm->cred = prepare_exec_creds();
1355         if (likely(bprm->cred))
1356                 return 0;
1357 
1358         mutex_unlock(&current->signal->cred_guard_mutex);
1359         return -ENOMEM;
1360 }
1361 
1362 static void free_bprm(struct linux_binprm *bprm)
1363 {
1364         free_arg_pages(bprm);
1365         if (bprm->cred) {
1366                 mutex_unlock(&current->signal->cred_guard_mutex);
1367                 abort_creds(bprm->cred);
1368         }
1369         if (bprm->file) {
1370                 allow_write_access(bprm->file);
1371                 fput(bprm->file);
1372         }
1373         /* If a binfmt changed the interp, free it. */
1374         if (bprm->interp != bprm->filename)
1375                 kfree(bprm->interp);
1376         kfree(bprm);
1377 }
1378 
1379 int bprm_change_interp(char *interp, struct linux_binprm *bprm)
1380 {
1381         /* If a binfmt changed the interp, free it first. */
1382         if (bprm->interp != bprm->filename)
1383                 kfree(bprm->interp);
1384         bprm->interp = kstrdup(interp, GFP_KERNEL);
1385         if (!bprm->interp)
1386                 return -ENOMEM;
1387         return 0;
1388 }
1389 EXPORT_SYMBOL(bprm_change_interp);
1390 
1391 /*
1392  * install the new credentials for this executable
1393  */
1394 void install_exec_creds(struct linux_binprm *bprm)
1395 {
1396         security_bprm_committing_creds(bprm);
1397 
1398         commit_creds(bprm->cred);
1399         bprm->cred = NULL;
1400 
1401         /*
1402          * Disable monitoring for regular users
1403          * when executing setuid binaries. Must
1404          * wait until new credentials are committed
1405          * by commit_creds() above
1406          */
1407         if (get_dumpable(current->mm) != SUID_DUMP_USER)
1408                 perf_event_exit_task(current);
1409         /*
1410          * cred_guard_mutex must be held at least to this point to prevent
1411          * ptrace_attach() from altering our determination of the task's
1412          * credentials; any time after this it may be unlocked.
1413          */
1414         security_bprm_committed_creds(bprm);
1415         mutex_unlock(&current->signal->cred_guard_mutex);
1416 }
1417 EXPORT_SYMBOL(install_exec_creds);
1418 
1419 /*
1420  * determine how safe it is to execute the proposed program
1421  * - the caller must hold ->cred_guard_mutex to protect against
1422  *   PTRACE_ATTACH or seccomp thread-sync
1423  */
1424 static void check_unsafe_exec(struct linux_binprm *bprm)
1425 {
1426         struct task_struct *p = current, *t;
1427         unsigned n_fs;
1428 
1429         if (p->ptrace) {
1430                 if (ptracer_capable(p, current_user_ns()))
1431                         bprm->unsafe |= LSM_UNSAFE_PTRACE_CAP;
1432                 else
1433                         bprm->unsafe |= LSM_UNSAFE_PTRACE;
1434         }
1435 
1436         /*
1437          * This isn't strictly necessary, but it makes it harder for LSMs to
1438          * mess up.
1439          */
1440         if (task_no_new_privs(current))
1441                 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1442 
1443         t = p;
1444         n_fs = 1;
1445         spin_lock(&p->fs->lock);
1446         rcu_read_lock();
1447         while_each_thread(p, t) {
1448                 if (t->fs == p->fs)
1449                         n_fs++;
1450         }
1451         rcu_read_unlock();
1452 
1453         if (p->fs->users > n_fs)
1454                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1455         else
1456                 p->fs->in_exec = 1;
1457         spin_unlock(&p->fs->lock);
1458 }
1459 
1460 static void bprm_fill_uid(struct linux_binprm *bprm)
1461 {
1462         struct inode *inode;
1463         unsigned int mode;
1464         kuid_t uid;
1465         kgid_t gid;
1466 
1467         /*
1468          * Since this can be called multiple times (via prepare_binprm),
1469          * we must clear any previous work done when setting set[ug]id
1470          * bits from any earlier bprm->file uses (for example when run
1471          * first for a setuid script then again for its interpreter).
1472          */
1473         bprm->cred->euid = current_euid();
1474         bprm->cred->egid = current_egid();
1475 
1476         if (!mnt_may_suid(bprm->file->f_path.mnt))
1477                 return;
1478 
1479         if (task_no_new_privs(current))
1480                 return;
1481 
1482         inode = file_inode(bprm->file);
1483         mode = READ_ONCE(inode->i_mode);
1484         if (!(mode & (S_ISUID|S_ISGID)))
1485                 return;
1486 
1487         /* Be careful if suid/sgid is set */
1488         inode_lock(inode);
1489 
1490         /* reload atomically mode/uid/gid now that lock held */
1491         mode = inode->i_mode;
1492         uid = inode->i_uid;
1493         gid = inode->i_gid;
1494         inode_unlock(inode);
1495 
1496         /* We ignore suid/sgid if there are no mappings for them in the ns */
1497         if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
1498                  !kgid_has_mapping(bprm->cred->user_ns, gid))
1499                 return;
1500 
1501         if (mode & S_ISUID) {
1502                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1503                 bprm->cred->euid = uid;
1504         }
1505 
1506         if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1507                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1508                 bprm->cred->egid = gid;
1509         }
1510 }
1511 
1512 /*
1513  * Fill the binprm structure from the inode.
1514  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1515  *
1516  * This may be called multiple times for binary chains (scripts for example).
1517  */
1518 int prepare_binprm(struct linux_binprm *bprm)
1519 {
1520         int retval;
1521 
1522         bprm_fill_uid(bprm);
1523 
1524         /* fill in binprm security blob */
1525         retval = security_bprm_set_creds(bprm);
1526         if (retval)
1527                 return retval;
1528         bprm->cred_prepared = 1;
1529 
1530         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1531         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1532 }
1533 
1534 EXPORT_SYMBOL(prepare_binprm);
1535 
1536 /*
1537  * Arguments are '\0' separated strings found at the location bprm->p
1538  * points to; chop off the first by relocating brpm->p to right after
1539  * the first '\0' encountered.
1540  */
1541 int remove_arg_zero(struct linux_binprm *bprm)
1542 {
1543         int ret = 0;
1544         unsigned long offset;
1545         char *kaddr;
1546         struct page *page;
1547 
1548         if (!bprm->argc)
1549                 return 0;
1550 
1551         do {
1552                 offset = bprm->p & ~PAGE_MASK;
1553                 page = get_arg_page(bprm, bprm->p, 0);
1554                 if (!page) {
1555                         ret = -EFAULT;
1556                         goto out;
1557                 }
1558                 kaddr = kmap_atomic(page);
1559 
1560                 for (; offset < PAGE_SIZE && kaddr[offset];
1561                                 offset++, bprm->p++)
1562                         ;
1563 
1564                 kunmap_atomic(kaddr);
1565                 put_arg_page(page);
1566         } while (offset == PAGE_SIZE);
1567 
1568         bprm->p++;
1569         bprm->argc--;
1570         ret = 0;
1571 
1572 out:
1573         return ret;
1574 }
1575 EXPORT_SYMBOL(remove_arg_zero);
1576 
1577 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1578 /*
1579  * cycle the list of binary formats handler, until one recognizes the image
1580  */
1581 int search_binary_handler(struct linux_binprm *bprm)
1582 {
1583         bool need_retry = IS_ENABLED(CONFIG_MODULES);
1584         struct linux_binfmt *fmt;
1585         int retval;
1586 
1587         /* This allows 4 levels of binfmt rewrites before failing hard. */
1588         if (bprm->recursion_depth > 5)
1589                 return -ELOOP;
1590 
1591         retval = security_bprm_check(bprm);
1592         if (retval)
1593                 return retval;
1594 
1595         retval = -ENOENT;
1596  retry:
1597         read_lock(&binfmt_lock);
1598         list_for_each_entry(fmt, &formats, lh) {
1599                 if (!try_module_get(fmt->module))
1600                         continue;
1601                 read_unlock(&binfmt_lock);
1602                 bprm->recursion_depth++;
1603                 retval = fmt->load_binary(bprm);
1604                 read_lock(&binfmt_lock);
1605                 put_binfmt(fmt);
1606                 bprm->recursion_depth--;
1607                 if (retval < 0 && !bprm->mm) {
1608                         /* we got to flush_old_exec() and failed after it */
1609                         read_unlock(&binfmt_lock);
1610                         force_sigsegv(SIGSEGV, current);
1611                         return retval;
1612                 }
1613                 if (retval != -ENOEXEC || !bprm->file) {
1614                         read_unlock(&binfmt_lock);
1615                         return retval;
1616                 }
1617         }
1618         read_unlock(&binfmt_lock);
1619 
1620         if (need_retry) {
1621                 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1622                     printable(bprm->buf[2]) && printable(bprm->buf[3]))
1623                         return retval;
1624                 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1625                         return retval;
1626                 need_retry = false;
1627                 goto retry;
1628         }
1629 
1630         return retval;
1631 }
1632 EXPORT_SYMBOL(search_binary_handler);
1633 
1634 static int exec_binprm(struct linux_binprm *bprm)
1635 {
1636         pid_t old_pid, old_vpid;
1637         int ret;
1638 
1639         /* Need to fetch pid before load_binary changes it */
1640         old_pid = current->pid;
1641         rcu_read_lock();
1642         old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1643         rcu_read_unlock();
1644 
1645         ret = search_binary_handler(bprm);
1646         if (ret >= 0) {
1647                 audit_bprm(bprm);
1648                 trace_sched_process_exec(current, old_pid, bprm);
1649                 ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1650                 proc_exec_connector(current);
1651         }
1652 
1653         return ret;
1654 }
1655 
1656 /*
1657  * sys_execve() executes a new program.
1658  */
1659 static int do_execveat_common(int fd, struct filename *filename,
1660                               struct user_arg_ptr argv,
1661                               struct user_arg_ptr envp,
1662                               int flags)
1663 {
1664         char *pathbuf = NULL;
1665         struct linux_binprm *bprm;
1666         struct file *file;
1667         struct files_struct *displaced;
1668         int retval;
1669 
1670         if (IS_ERR(filename))
1671                 return PTR_ERR(filename);
1672 
1673         /*
1674          * We move the actual failure in case of RLIMIT_NPROC excess from
1675          * set*uid() to execve() because too many poorly written programs
1676          * don't check setuid() return code.  Here we additionally recheck
1677          * whether NPROC limit is still exceeded.
1678          */
1679         if ((current->flags & PF_NPROC_EXCEEDED) &&
1680             atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
1681                 retval = -EAGAIN;
1682                 goto out_ret;
1683         }
1684 
1685         /* We're below the limit (still or again), so we don't want to make
1686          * further execve() calls fail. */
1687         current->flags &= ~PF_NPROC_EXCEEDED;
1688 
1689         retval = unshare_files(&displaced);
1690         if (retval)
1691                 goto out_ret;
1692 
1693         retval = -ENOMEM;
1694         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1695         if (!bprm)
1696                 goto out_files;
1697 
1698         retval = prepare_bprm_creds(bprm);
1699         if (retval)
1700                 goto out_free;
1701 
1702         check_unsafe_exec(bprm);
1703         current->in_execve = 1;
1704 
1705         file = do_open_execat(fd, filename, flags);
1706         retval = PTR_ERR(file);
1707         if (IS_ERR(file))
1708                 goto out_unmark;
1709 
1710         sched_exec();
1711 
1712         bprm->file = file;
1713         if (fd == AT_FDCWD || filename->name[0] == '/') {
1714                 bprm->filename = filename->name;
1715         } else {
1716                 if (filename->name[0] == '\0')
1717                         pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d", fd);
1718                 else
1719                         pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d/%s",
1720                                             fd, filename->name);
1721                 if (!pathbuf) {
1722                         retval = -ENOMEM;
1723                         goto out_unmark;
1724                 }
1725                 /*
1726                  * Record that a name derived from an O_CLOEXEC fd will be
1727                  * inaccessible after exec. Relies on having exclusive access to
1728                  * current->files (due to unshare_files above).
1729                  */
1730                 if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt)))
1731                         bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1732                 bprm->filename = pathbuf;
1733         }
1734         bprm->interp = bprm->filename;
1735 
1736         retval = bprm_mm_init(bprm);
1737         if (retval)
1738                 goto out_unmark;
1739 
1740         bprm->argc = count(argv, MAX_ARG_STRINGS);
1741         if ((retval = bprm->argc) < 0)
1742                 goto out;
1743 
1744         bprm->envc = count(envp, MAX_ARG_STRINGS);
1745         if ((retval = bprm->envc) < 0)
1746                 goto out;
1747 
1748         retval = prepare_binprm(bprm);
1749         if (retval < 0)
1750                 goto out;
1751 
1752         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1753         if (retval < 0)
1754                 goto out;
1755 
1756         bprm->exec = bprm->p;
1757         retval = copy_strings(bprm->envc, envp, bprm);
1758         if (retval < 0)
1759                 goto out;
1760 
1761         retval = copy_strings(bprm->argc, argv, bprm);
1762         if (retval < 0)
1763                 goto out;
1764 
1765         would_dump(bprm, bprm->file);
1766 
1767         retval = exec_binprm(bprm);
1768         if (retval < 0)
1769                 goto out;
1770 
1771         /* execve succeeded */
1772         current->fs->in_exec = 0;
1773         current->in_execve = 0;
1774         acct_update_integrals(current);
1775         task_numa_free(current);
1776         free_bprm(bprm);
1777         kfree(pathbuf);
1778         putname(filename);
1779         if (displaced)
1780                 put_files_struct(displaced);
1781         return retval;
1782 
1783 out:
1784         if (bprm->mm) {
1785                 acct_arg_size(bprm, 0);
1786                 mmput(bprm->mm);
1787         }
1788 
1789 out_unmark:
1790         current->fs->in_exec = 0;
1791         current->in_execve = 0;
1792 
1793 out_free:
1794         free_bprm(bprm);
1795         kfree(pathbuf);
1796 
1797 out_files:
1798         if (displaced)
1799                 reset_files_struct(displaced);
1800 out_ret:
1801         putname(filename);
1802         return retval;
1803 }
1804 
1805 int do_execve(struct filename *filename,
1806         const char __user *const __user *__argv,
1807         const char __user *const __user *__envp)
1808 {
1809         struct user_arg_ptr argv = { .ptr.native = __argv };
1810         struct user_arg_ptr envp = { .ptr.native = __envp };
1811         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1812 }
1813 
1814 int do_execveat(int fd, struct filename *filename,
1815                 const char __user *const __user *__argv,
1816                 const char __user *const __user *__envp,
1817                 int flags)
1818 {
1819         struct user_arg_ptr argv = { .ptr.native = __argv };
1820         struct user_arg_ptr envp = { .ptr.native = __envp };
1821 
1822         return do_execveat_common(fd, filename, argv, envp, flags);
1823 }
1824 
1825 #ifdef CONFIG_COMPAT
1826 static int compat_do_execve(struct filename *filename,
1827         const compat_uptr_t __user *__argv,
1828         const compat_uptr_t __user *__envp)
1829 {
1830         struct user_arg_ptr argv = {
1831                 .is_compat = true,
1832                 .ptr.compat = __argv,
1833         };
1834         struct user_arg_ptr envp = {
1835                 .is_compat = true,
1836                 .ptr.compat = __envp,
1837         };
1838         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1839 }
1840 
1841 static int compat_do_execveat(int fd, struct filename *filename,
1842                               const compat_uptr_t __user *__argv,
1843                               const compat_uptr_t __user *__envp,
1844                               int flags)
1845 {
1846         struct user_arg_ptr argv = {
1847                 .is_compat = true,
1848                 .ptr.compat = __argv,
1849         };
1850         struct user_arg_ptr envp = {
1851                 .is_compat = true,
1852                 .ptr.compat = __envp,
1853         };
1854         return do_execveat_common(fd, filename, argv, envp, flags);
1855 }
1856 #endif
1857 
1858 void set_binfmt(struct linux_binfmt *new)
1859 {
1860         struct mm_struct *mm = current->mm;
1861 
1862         if (mm->binfmt)
1863                 module_put(mm->binfmt->module);
1864 
1865         mm->binfmt = new;
1866         if (new)
1867                 __module_get(new->module);
1868 }
1869 EXPORT_SYMBOL(set_binfmt);
1870 
1871 /*
1872  * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
1873  */
1874 void set_dumpable(struct mm_struct *mm, int value)
1875 {
1876         unsigned long old, new;
1877 
1878         if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
1879                 return;
1880 
1881         do {
1882                 old = ACCESS_ONCE(mm->flags);
1883                 new = (old & ~MMF_DUMPABLE_MASK) | value;
1884         } while (cmpxchg(&mm->flags, old, new) != old);
1885 }
1886 
1887 SYSCALL_DEFINE3(execve,
1888                 const char __user *, filename,
1889                 const char __user *const __user *, argv,
1890                 const char __user *const __user *, envp)
1891 {
1892         return do_execve(getname(filename), argv, envp);
1893 }
1894 
1895 SYSCALL_DEFINE5(execveat,
1896                 int, fd, const char __user *, filename,
1897                 const char __user *const __user *, argv,
1898                 const char __user *const __user *, envp,
1899                 int, flags)
1900 {
1901         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1902 
1903         return do_execveat(fd,
1904                            getname_flags(filename, lookup_flags, NULL),
1905                            argv, envp, flags);
1906 }
1907 
1908 #ifdef CONFIG_COMPAT
1909 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
1910         const compat_uptr_t __user *, argv,
1911         const compat_uptr_t __user *, envp)
1912 {
1913         return compat_do_execve(getname(filename), argv, envp);
1914 }
1915 
1916 COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
1917                        const char __user *, filename,
1918                        const compat_uptr_t __user *, argv,
1919                        const compat_uptr_t __user *, envp,
1920                        int,  flags)
1921 {
1922         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1923 
1924         return compat_do_execveat(fd,
1925                                   getname_flags(filename, lookup_flags, NULL),
1926                                   argv, envp, flags);
1927 }
1928 #endif
1929 

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