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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/sched/mm.h>
 36 #include <linux/sched/coredump.h>
 37 #include <linux/sched/signal.h>
 38 #include <linux/sched/numa_balancing.h>
 39 #include <linux/sched/task.h>
 40 #include <linux/pagemap.h>
 41 #include <linux/perf_event.h>
 42 #include <linux/highmem.h>
 43 #include <linux/spinlock.h>
 44 #include <linux/key.h>
 45 #include <linux/personality.h>
 46 #include <linux/binfmts.h>
 47 #include <linux/utsname.h>
 48 #include <linux/pid_namespace.h>
 49 #include <linux/module.h>
 50 #include <linux/namei.h>
 51 #include <linux/mount.h>
 52 #include <linux/security.h>
 53 #include <linux/syscalls.h>
 54 #include <linux/tsacct_kern.h>
 55 #include <linux/cn_proc.h>
 56 #include <linux/audit.h>
 57 #include <linux/tracehook.h>
 58 #include <linux/kmod.h>
 59 #include <linux/fsnotify.h>
 60 #include <linux/fs_struct.h>
 61 #include <linux/pipe_fs_i.h>
 62 #include <linux/oom.h>
 63 #include <linux/compat.h>
 64 #include <linux/vmalloc.h>
 65 
 66 #include <linux/uaccess.h>
 67 #include <asm/mmu_context.h>
 68 #include <asm/tlb.h>
 69 
 70 #include <trace/events/task.h>
 71 #include "internal.h"
 72 
 73 #include <trace/events/sched.h>
 74 
 75 int suid_dumpable = 0;
 76 
 77 static LIST_HEAD(formats);
 78 static DEFINE_RWLOCK(binfmt_lock);
 79 
 80 void __register_binfmt(struct linux_binfmt * fmt, int insert)
 81 {
 82         BUG_ON(!fmt);
 83         if (WARN_ON(!fmt->load_binary))
 84                 return;
 85         write_lock(&binfmt_lock);
 86         insert ? list_add(&fmt->lh, &formats) :
 87                  list_add_tail(&fmt->lh, &formats);
 88         write_unlock(&binfmt_lock);
 89 }
 90 
 91 EXPORT_SYMBOL(__register_binfmt);
 92 
 93 void unregister_binfmt(struct linux_binfmt * fmt)
 94 {
 95         write_lock(&binfmt_lock);
 96         list_del(&fmt->lh);
 97         write_unlock(&binfmt_lock);
 98 }
 99 
100 EXPORT_SYMBOL(unregister_binfmt);
101 
102 static inline void put_binfmt(struct linux_binfmt * fmt)
103 {
104         module_put(fmt->module);
105 }
106 
107 bool path_noexec(const struct path *path)
108 {
109         return (path->mnt->mnt_flags & MNT_NOEXEC) ||
110                (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
111 }
112 
113 #ifdef CONFIG_USELIB
114 /*
115  * Note that a shared library must be both readable and executable due to
116  * security reasons.
117  *
118  * Also note that we take the address to load from from the file itself.
119  */
120 SYSCALL_DEFINE1(uselib, const char __user *, library)
121 {
122         struct linux_binfmt *fmt;
123         struct file *file;
124         struct filename *tmp = getname(library);
125         int error = PTR_ERR(tmp);
126         static const struct open_flags uselib_flags = {
127                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
128                 .acc_mode = MAY_READ | MAY_EXEC,
129                 .intent = LOOKUP_OPEN,
130                 .lookup_flags = LOOKUP_FOLLOW,
131         };
132 
133         if (IS_ERR(tmp))
134                 goto out;
135 
136         file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
137         putname(tmp);
138         error = PTR_ERR(file);
139         if (IS_ERR(file))
140                 goto out;
141 
142         error = -EINVAL;
143         if (!S_ISREG(file_inode(file)->i_mode))
144                 goto exit;
145 
146         error = -EACCES;
147         if (path_noexec(&file->f_path))
148                 goto exit;
149 
150         fsnotify_open(file);
151 
152         error = -ENOEXEC;
153 
154         read_lock(&binfmt_lock);
155         list_for_each_entry(fmt, &formats, lh) {
156                 if (!fmt->load_shlib)
157                         continue;
158                 if (!try_module_get(fmt->module))
159                         continue;
160                 read_unlock(&binfmt_lock);
161                 error = fmt->load_shlib(file);
162                 read_lock(&binfmt_lock);
163                 put_binfmt(fmt);
164                 if (error != -ENOEXEC)
165                         break;
166         }
167         read_unlock(&binfmt_lock);
168 exit:
169         fput(file);
170 out:
171         return error;
172 }
173 #endif /* #ifdef CONFIG_USELIB */
174 
175 #ifdef CONFIG_MMU
176 /*
177  * The nascent bprm->mm is not visible until exec_mmap() but it can
178  * use a lot of memory, account these pages in current->mm temporary
179  * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
180  * change the counter back via acct_arg_size(0).
181  */
182 static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
183 {
184         struct mm_struct *mm = current->mm;
185         long diff = (long)(pages - bprm->vma_pages);
186 
187         if (!mm || !diff)
188                 return;
189 
190         bprm->vma_pages = pages;
191         add_mm_counter(mm, MM_ANONPAGES, diff);
192 }
193 
194 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
195                 int write)
196 {
197         struct page *page;
198         int ret;
199         unsigned int gup_flags = FOLL_FORCE;
200 
201 #ifdef CONFIG_STACK_GROWSUP
202         if (write) {
203                 ret = expand_downwards(bprm->vma, pos);
204                 if (ret < 0)
205                         return NULL;
206         }
207 #endif
208 
209         if (write)
210                 gup_flags |= FOLL_WRITE;
211 
212         /*
213          * We are doing an exec().  'current' is the process
214          * doing the exec and bprm->mm is the new process's mm.
215          */
216         ret = get_user_pages_remote(current, bprm->mm, pos, 1, gup_flags,
217                         &page, NULL, NULL);
218         if (ret <= 0)
219                 return NULL;
220 
221         if (write)
222                 acct_arg_size(bprm, vma_pages(bprm->vma));
223 
224         return page;
225 }
226 
227 static void put_arg_page(struct page *page)
228 {
229         put_page(page);
230 }
231 
232 static void free_arg_pages(struct linux_binprm *bprm)
233 {
234 }
235 
236 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
237                 struct page *page)
238 {
239         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
240 }
241 
242 static int __bprm_mm_init(struct linux_binprm *bprm)
243 {
244         int err;
245         struct vm_area_struct *vma = NULL;
246         struct mm_struct *mm = bprm->mm;
247 
248         bprm->vma = vma = vm_area_alloc(mm);
249         if (!vma)
250                 return -ENOMEM;
251         vma_set_anonymous(vma);
252 
253         if (down_write_killable(&mm->mmap_sem)) {
254                 err = -EINTR;
255                 goto err_free;
256         }
257 
258         /*
259          * Place the stack at the largest stack address the architecture
260          * supports. Later, we'll move this to an appropriate place. We don't
261          * use STACK_TOP because that can depend on attributes which aren't
262          * configured yet.
263          */
264         BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
265         vma->vm_end = STACK_TOP_MAX;
266         vma->vm_start = vma->vm_end - PAGE_SIZE;
267         vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
268         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
269 
270         err = insert_vm_struct(mm, vma);
271         if (err)
272                 goto err;
273 
274         mm->stack_vm = mm->total_vm = 1;
275         arch_bprm_mm_init(mm, vma);
276         up_write(&mm->mmap_sem);
277         bprm->p = vma->vm_end - sizeof(void *);
278         return 0;
279 err:
280         up_write(&mm->mmap_sem);
281 err_free:
282         bprm->vma = NULL;
283         vm_area_free(vma);
284         return err;
285 }
286 
287 static bool valid_arg_len(struct linux_binprm *bprm, long len)
288 {
289         return len <= MAX_ARG_STRLEN;
290 }
291 
292 #else
293 
294 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
295 {
296 }
297 
298 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
299                 int write)
300 {
301         struct page *page;
302 
303         page = bprm->page[pos / PAGE_SIZE];
304         if (!page && write) {
305                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
306                 if (!page)
307                         return NULL;
308                 bprm->page[pos / PAGE_SIZE] = page;
309         }
310 
311         return page;
312 }
313 
314 static void put_arg_page(struct page *page)
315 {
316 }
317 
318 static void free_arg_page(struct linux_binprm *bprm, int i)
319 {
320         if (bprm->page[i]) {
321                 __free_page(bprm->page[i]);
322                 bprm->page[i] = NULL;
323         }
324 }
325 
326 static void free_arg_pages(struct linux_binprm *bprm)
327 {
328         int i;
329 
330         for (i = 0; i < MAX_ARG_PAGES; i++)
331                 free_arg_page(bprm, i);
332 }
333 
334 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
335                 struct page *page)
336 {
337 }
338 
339 static int __bprm_mm_init(struct linux_binprm *bprm)
340 {
341         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
342         return 0;
343 }
344 
345 static bool valid_arg_len(struct linux_binprm *bprm, long len)
346 {
347         return len <= bprm->p;
348 }
349 
350 #endif /* CONFIG_MMU */
351 
352 /*
353  * Create a new mm_struct and populate it with a temporary stack
354  * vm_area_struct.  We don't have enough context at this point to set the stack
355  * flags, permissions, and offset, so we use temporary values.  We'll update
356  * them later in setup_arg_pages().
357  */
358 static int bprm_mm_init(struct linux_binprm *bprm)
359 {
360         int err;
361         struct mm_struct *mm = NULL;
362 
363         bprm->mm = mm = mm_alloc();
364         err = -ENOMEM;
365         if (!mm)
366                 goto err;
367 
368         /* Save current stack limit for all calculations made during exec. */
369         task_lock(current->group_leader);
370         bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK];
371         task_unlock(current->group_leader);
372 
373         err = __bprm_mm_init(bprm);
374         if (err)
375                 goto err;
376 
377         return 0;
378 
379 err:
380         if (mm) {
381                 bprm->mm = NULL;
382                 mmdrop(mm);
383         }
384 
385         return err;
386 }
387 
388 struct user_arg_ptr {
389 #ifdef CONFIG_COMPAT
390         bool is_compat;
391 #endif
392         union {
393                 const char __user *const __user *native;
394 #ifdef CONFIG_COMPAT
395                 const compat_uptr_t __user *compat;
396 #endif
397         } ptr;
398 };
399 
400 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
401 {
402         const char __user *native;
403 
404 #ifdef CONFIG_COMPAT
405         if (unlikely(argv.is_compat)) {
406                 compat_uptr_t compat;
407 
408                 if (get_user(compat, argv.ptr.compat + nr))
409                         return ERR_PTR(-EFAULT);
410 
411                 return compat_ptr(compat);
412         }
413 #endif
414 
415         if (get_user(native, argv.ptr.native + nr))
416                 return ERR_PTR(-EFAULT);
417 
418         return native;
419 }
420 
421 /*
422  * count() counts the number of strings in array ARGV.
423  */
424 static int count(struct user_arg_ptr argv, int max)
425 {
426         int i = 0;
427 
428         if (argv.ptr.native != NULL) {
429                 for (;;) {
430                         const char __user *p = get_user_arg_ptr(argv, i);
431 
432                         if (!p)
433                                 break;
434 
435                         if (IS_ERR(p))
436                                 return -EFAULT;
437 
438                         if (i >= max)
439                                 return -E2BIG;
440                         ++i;
441 
442                         if (fatal_signal_pending(current))
443                                 return -ERESTARTNOHAND;
444                         cond_resched();
445                 }
446         }
447         return i;
448 }
449 
450 static int prepare_arg_pages(struct linux_binprm *bprm,
451                         struct user_arg_ptr argv, struct user_arg_ptr envp)
452 {
453         unsigned long limit, ptr_size;
454 
455         bprm->argc = count(argv, MAX_ARG_STRINGS);
456         if (bprm->argc < 0)
457                 return bprm->argc;
458 
459         bprm->envc = count(envp, MAX_ARG_STRINGS);
460         if (bprm->envc < 0)
461                 return bprm->envc;
462 
463         /*
464          * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
465          * (whichever is smaller) for the argv+env strings.
466          * This ensures that:
467          *  - the remaining binfmt code will not run out of stack space,
468          *  - the program will have a reasonable amount of stack left
469          *    to work from.
470          */
471         limit = _STK_LIM / 4 * 3;
472         limit = min(limit, bprm->rlim_stack.rlim_cur / 4);
473         /*
474          * We've historically supported up to 32 pages (ARG_MAX)
475          * of argument strings even with small stacks
476          */
477         limit = max_t(unsigned long, limit, ARG_MAX);
478         /*
479          * We must account for the size of all the argv and envp pointers to
480          * the argv and envp strings, since they will also take up space in
481          * the stack. They aren't stored until much later when we can't
482          * signal to the parent that the child has run out of stack space.
483          * Instead, calculate it here so it's possible to fail gracefully.
484          */
485         ptr_size = (bprm->argc + bprm->envc) * sizeof(void *);
486         if (limit <= ptr_size)
487                 return -E2BIG;
488         limit -= ptr_size;
489 
490         bprm->argmin = bprm->p - limit;
491         return 0;
492 }
493 
494 /*
495  * 'copy_strings()' copies argument/environment strings from the old
496  * processes's memory to the new process's stack.  The call to get_user_pages()
497  * ensures the destination page is created and not swapped out.
498  */
499 static int copy_strings(int argc, struct user_arg_ptr argv,
500                         struct linux_binprm *bprm)
501 {
502         struct page *kmapped_page = NULL;
503         char *kaddr = NULL;
504         unsigned long kpos = 0;
505         int ret;
506 
507         while (argc-- > 0) {
508                 const char __user *str;
509                 int len;
510                 unsigned long pos;
511 
512                 ret = -EFAULT;
513                 str = get_user_arg_ptr(argv, argc);
514                 if (IS_ERR(str))
515                         goto out;
516 
517                 len = strnlen_user(str, MAX_ARG_STRLEN);
518                 if (!len)
519                         goto out;
520 
521                 ret = -E2BIG;
522                 if (!valid_arg_len(bprm, len))
523                         goto out;
524 
525                 /* We're going to work our way backwords. */
526                 pos = bprm->p;
527                 str += len;
528                 bprm->p -= len;
529 #ifdef CONFIG_MMU
530                 if (bprm->p < bprm->argmin)
531                         goto out;
532 #endif
533 
534                 while (len > 0) {
535                         int offset, bytes_to_copy;
536 
537                         if (fatal_signal_pending(current)) {
538                                 ret = -ERESTARTNOHAND;
539                                 goto out;
540                         }
541                         cond_resched();
542 
543                         offset = pos % PAGE_SIZE;
544                         if (offset == 0)
545                                 offset = PAGE_SIZE;
546 
547                         bytes_to_copy = offset;
548                         if (bytes_to_copy > len)
549                                 bytes_to_copy = len;
550 
551                         offset -= bytes_to_copy;
552                         pos -= bytes_to_copy;
553                         str -= bytes_to_copy;
554                         len -= bytes_to_copy;
555 
556                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
557                                 struct page *page;
558 
559                                 page = get_arg_page(bprm, pos, 1);
560                                 if (!page) {
561                                         ret = -E2BIG;
562                                         goto out;
563                                 }
564 
565                                 if (kmapped_page) {
566                                         flush_kernel_dcache_page(kmapped_page);
567                                         kunmap(kmapped_page);
568                                         put_arg_page(kmapped_page);
569                                 }
570                                 kmapped_page = page;
571                                 kaddr = kmap(kmapped_page);
572                                 kpos = pos & PAGE_MASK;
573                                 flush_arg_page(bprm, kpos, kmapped_page);
574                         }
575                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
576                                 ret = -EFAULT;
577                                 goto out;
578                         }
579                 }
580         }
581         ret = 0;
582 out:
583         if (kmapped_page) {
584                 flush_kernel_dcache_page(kmapped_page);
585                 kunmap(kmapped_page);
586                 put_arg_page(kmapped_page);
587         }
588         return ret;
589 }
590 
591 /*
592  * Like copy_strings, but get argv and its values from kernel memory.
593  */
594 int copy_strings_kernel(int argc, const char *const *__argv,
595                         struct linux_binprm *bprm)
596 {
597         int r;
598         mm_segment_t oldfs = get_fs();
599         struct user_arg_ptr argv = {
600                 .ptr.native = (const char __user *const  __user *)__argv,
601         };
602 
603         set_fs(KERNEL_DS);
604         r = copy_strings(argc, argv, bprm);
605         set_fs(oldfs);
606 
607         return r;
608 }
609 EXPORT_SYMBOL(copy_strings_kernel);
610 
611 #ifdef CONFIG_MMU
612 
613 /*
614  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
615  * the binfmt code determines where the new stack should reside, we shift it to
616  * its final location.  The process proceeds as follows:
617  *
618  * 1) Use shift to calculate the new vma endpoints.
619  * 2) Extend vma to cover both the old and new ranges.  This ensures the
620  *    arguments passed to subsequent functions are consistent.
621  * 3) Move vma's page tables to the new range.
622  * 4) Free up any cleared pgd range.
623  * 5) Shrink the vma to cover only the new range.
624  */
625 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
626 {
627         struct mm_struct *mm = vma->vm_mm;
628         unsigned long old_start = vma->vm_start;
629         unsigned long old_end = vma->vm_end;
630         unsigned long length = old_end - old_start;
631         unsigned long new_start = old_start - shift;
632         unsigned long new_end = old_end - shift;
633         struct mmu_gather tlb;
634 
635         BUG_ON(new_start > new_end);
636 
637         /*
638          * ensure there are no vmas between where we want to go
639          * and where we are
640          */
641         if (vma != find_vma(mm, new_start))
642                 return -EFAULT;
643 
644         /*
645          * cover the whole range: [new_start, old_end)
646          */
647         if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
648                 return -ENOMEM;
649 
650         /*
651          * move the page tables downwards, on failure we rely on
652          * process cleanup to remove whatever mess we made.
653          */
654         if (length != move_page_tables(vma, old_start,
655                                        vma, new_start, length, false))
656                 return -ENOMEM;
657 
658         lru_add_drain();
659         tlb_gather_mmu(&tlb, mm, old_start, old_end);
660         if (new_end > old_start) {
661                 /*
662                  * when the old and new regions overlap clear from new_end.
663                  */
664                 free_pgd_range(&tlb, new_end, old_end, new_end,
665                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
666         } else {
667                 /*
668                  * otherwise, clean from old_start; this is done to not touch
669                  * the address space in [new_end, old_start) some architectures
670                  * have constraints on va-space that make this illegal (IA64) -
671                  * for the others its just a little faster.
672                  */
673                 free_pgd_range(&tlb, old_start, old_end, new_end,
674                         vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
675         }
676         tlb_finish_mmu(&tlb, old_start, old_end);
677 
678         /*
679          * Shrink the vma to just the new range.  Always succeeds.
680          */
681         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
682 
683         return 0;
684 }
685 
686 /*
687  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
688  * the stack is optionally relocated, and some extra space is added.
689  */
690 int setup_arg_pages(struct linux_binprm *bprm,
691                     unsigned long stack_top,
692                     int executable_stack)
693 {
694         unsigned long ret;
695         unsigned long stack_shift;
696         struct mm_struct *mm = current->mm;
697         struct vm_area_struct *vma = bprm->vma;
698         struct vm_area_struct *prev = NULL;
699         unsigned long vm_flags;
700         unsigned long stack_base;
701         unsigned long stack_size;
702         unsigned long stack_expand;
703         unsigned long rlim_stack;
704 
705 #ifdef CONFIG_STACK_GROWSUP
706         /* Limit stack size */
707         stack_base = bprm->rlim_stack.rlim_max;
708         if (stack_base > STACK_SIZE_MAX)
709                 stack_base = STACK_SIZE_MAX;
710 
711         /* Add space for stack randomization. */
712         stack_base += (STACK_RND_MASK << PAGE_SHIFT);
713 
714         /* Make sure we didn't let the argument array grow too large. */
715         if (vma->vm_end - vma->vm_start > stack_base)
716                 return -ENOMEM;
717 
718         stack_base = PAGE_ALIGN(stack_top - stack_base);
719 
720         stack_shift = vma->vm_start - stack_base;
721         mm->arg_start = bprm->p - stack_shift;
722         bprm->p = vma->vm_end - stack_shift;
723 #else
724         stack_top = arch_align_stack(stack_top);
725         stack_top = PAGE_ALIGN(stack_top);
726 
727         if (unlikely(stack_top < mmap_min_addr) ||
728             unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
729                 return -ENOMEM;
730 
731         stack_shift = vma->vm_end - stack_top;
732 
733         bprm->p -= stack_shift;
734         mm->arg_start = bprm->p;
735 #endif
736 
737         if (bprm->loader)
738                 bprm->loader -= stack_shift;
739         bprm->exec -= stack_shift;
740 
741         if (down_write_killable(&mm->mmap_sem))
742                 return -EINTR;
743 
744         vm_flags = VM_STACK_FLAGS;
745 
746         /*
747          * Adjust stack execute permissions; explicitly enable for
748          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
749          * (arch default) otherwise.
750          */
751         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
752                 vm_flags |= VM_EXEC;
753         else if (executable_stack == EXSTACK_DISABLE_X)
754                 vm_flags &= ~VM_EXEC;
755         vm_flags |= mm->def_flags;
756         vm_flags |= VM_STACK_INCOMPLETE_SETUP;
757 
758         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
759                         vm_flags);
760         if (ret)
761                 goto out_unlock;
762         BUG_ON(prev != vma);
763 
764         /* Move stack pages down in memory. */
765         if (stack_shift) {
766                 ret = shift_arg_pages(vma, stack_shift);
767                 if (ret)
768                         goto out_unlock;
769         }
770 
771         /* mprotect_fixup is overkill to remove the temporary stack flags */
772         vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
773 
774         stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
775         stack_size = vma->vm_end - vma->vm_start;
776         /*
777          * Align this down to a page boundary as expand_stack
778          * will align it up.
779          */
780         rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK;
781 #ifdef CONFIG_STACK_GROWSUP
782         if (stack_size + stack_expand > rlim_stack)
783                 stack_base = vma->vm_start + rlim_stack;
784         else
785                 stack_base = vma->vm_end + stack_expand;
786 #else
787         if (stack_size + stack_expand > rlim_stack)
788                 stack_base = vma->vm_end - rlim_stack;
789         else
790                 stack_base = vma->vm_start - stack_expand;
791 #endif
792         current->mm->start_stack = bprm->p;
793         ret = expand_stack(vma, stack_base);
794         if (ret)
795                 ret = -EFAULT;
796 
797 out_unlock:
798         up_write(&mm->mmap_sem);
799         return ret;
800 }
801 EXPORT_SYMBOL(setup_arg_pages);
802 
803 #else
804 
805 /*
806  * Transfer the program arguments and environment from the holding pages
807  * onto the stack. The provided stack pointer is adjusted accordingly.
808  */
809 int transfer_args_to_stack(struct linux_binprm *bprm,
810                            unsigned long *sp_location)
811 {
812         unsigned long index, stop, sp;
813         int ret = 0;
814 
815         stop = bprm->p >> PAGE_SHIFT;
816         sp = *sp_location;
817 
818         for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
819                 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
820                 char *src = kmap(bprm->page[index]) + offset;
821                 sp -= PAGE_SIZE - offset;
822                 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
823                         ret = -EFAULT;
824                 kunmap(bprm->page[index]);
825                 if (ret)
826                         goto out;
827         }
828 
829         *sp_location = sp;
830 
831 out:
832         return ret;
833 }
834 EXPORT_SYMBOL(transfer_args_to_stack);
835 
836 #endif /* CONFIG_MMU */
837 
838 static struct file *do_open_execat(int fd, struct filename *name, int flags)
839 {
840         struct file *file;
841         int err;
842         struct open_flags open_exec_flags = {
843                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
844                 .acc_mode = MAY_EXEC,
845                 .intent = LOOKUP_OPEN,
846                 .lookup_flags = LOOKUP_FOLLOW,
847         };
848 
849         if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
850                 return ERR_PTR(-EINVAL);
851         if (flags & AT_SYMLINK_NOFOLLOW)
852                 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
853         if (flags & AT_EMPTY_PATH)
854                 open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
855 
856         file = do_filp_open(fd, name, &open_exec_flags);
857         if (IS_ERR(file))
858                 goto out;
859 
860         err = -EACCES;
861         if (!S_ISREG(file_inode(file)->i_mode))
862                 goto exit;
863 
864         if (path_noexec(&file->f_path))
865                 goto exit;
866 
867         err = deny_write_access(file);
868         if (err)
869                 goto exit;
870 
871         if (name->name[0] != '\0')
872                 fsnotify_open(file);
873 
874 out:
875         return file;
876 
877 exit:
878         fput(file);
879         return ERR_PTR(err);
880 }
881 
882 struct file *open_exec(const char *name)
883 {
884         struct filename *filename = getname_kernel(name);
885         struct file *f = ERR_CAST(filename);
886 
887         if (!IS_ERR(filename)) {
888                 f = do_open_execat(AT_FDCWD, filename, 0);
889                 putname(filename);
890         }
891         return f;
892 }
893 EXPORT_SYMBOL(open_exec);
894 
895 int kernel_read_file(struct file *file, void **buf, loff_t *size,
896                      loff_t max_size, enum kernel_read_file_id id)
897 {
898         loff_t i_size, pos;
899         ssize_t bytes = 0;
900         int ret;
901 
902         if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
903                 return -EINVAL;
904 
905         ret = deny_write_access(file);
906         if (ret)
907                 return ret;
908 
909         ret = security_kernel_read_file(file, id);
910         if (ret)
911                 goto out;
912 
913         i_size = i_size_read(file_inode(file));
914         if (i_size <= 0) {
915                 ret = -EINVAL;
916                 goto out;
917         }
918         if (i_size > SIZE_MAX || (max_size > 0 && i_size > max_size)) {
919                 ret = -EFBIG;
920                 goto out;
921         }
922 
923         if (id != READING_FIRMWARE_PREALLOC_BUFFER)
924                 *buf = vmalloc(i_size);
925         if (!*buf) {
926                 ret = -ENOMEM;
927                 goto out;
928         }
929 
930         pos = 0;
931         while (pos < i_size) {
932                 bytes = kernel_read(file, *buf + pos, i_size - pos, &pos);
933                 if (bytes < 0) {
934                         ret = bytes;
935                         goto out_free;
936                 }
937 
938                 if (bytes == 0)
939                         break;
940         }
941 
942         if (pos != i_size) {
943                 ret = -EIO;
944                 goto out_free;
945         }
946 
947         ret = security_kernel_post_read_file(file, *buf, i_size, id);
948         if (!ret)
949                 *size = pos;
950 
951 out_free:
952         if (ret < 0) {
953                 if (id != READING_FIRMWARE_PREALLOC_BUFFER) {
954                         vfree(*buf);
955                         *buf = NULL;
956                 }
957         }
958 
959 out:
960         allow_write_access(file);
961         return ret;
962 }
963 EXPORT_SYMBOL_GPL(kernel_read_file);
964 
965 int kernel_read_file_from_path(const char *path, void **buf, loff_t *size,
966                                loff_t max_size, enum kernel_read_file_id id)
967 {
968         struct file *file;
969         int ret;
970 
971         if (!path || !*path)
972                 return -EINVAL;
973 
974         file = filp_open(path, O_RDONLY, 0);
975         if (IS_ERR(file))
976                 return PTR_ERR(file);
977 
978         ret = kernel_read_file(file, buf, size, max_size, id);
979         fput(file);
980         return ret;
981 }
982 EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
983 
984 int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
985                              enum kernel_read_file_id id)
986 {
987         struct fd f = fdget(fd);
988         int ret = -EBADF;
989 
990         if (!f.file)
991                 goto out;
992 
993         ret = kernel_read_file(f.file, buf, size, max_size, id);
994 out:
995         fdput(f);
996         return ret;
997 }
998 EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);
999 
1000 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
1001 {
1002         ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
1003         if (res > 0)
1004                 flush_icache_range(addr, addr + len);
1005         return res;
1006 }
1007 EXPORT_SYMBOL(read_code);
1008 
1009 static int exec_mmap(struct mm_struct *mm)
1010 {
1011         struct task_struct *tsk;
1012         struct mm_struct *old_mm, *active_mm;
1013 
1014         /* Notify parent that we're no longer interested in the old VM */
1015         tsk = current;
1016         old_mm = current->mm;
1017         mm_release(tsk, old_mm);
1018 
1019         if (old_mm) {
1020                 sync_mm_rss(old_mm);
1021                 /*
1022                  * Make sure that if there is a core dump in progress
1023                  * for the old mm, we get out and die instead of going
1024                  * through with the exec.  We must hold mmap_sem around
1025                  * checking core_state and changing tsk->mm.
1026                  */
1027                 down_read(&old_mm->mmap_sem);
1028                 if (unlikely(old_mm->core_state)) {
1029                         up_read(&old_mm->mmap_sem);
1030                         return -EINTR;
1031                 }
1032         }
1033         task_lock(tsk);
1034         active_mm = tsk->active_mm;
1035         tsk->mm = mm;
1036         tsk->active_mm = mm;
1037         activate_mm(active_mm, mm);
1038         tsk->mm->vmacache_seqnum = 0;
1039         vmacache_flush(tsk);
1040         task_unlock(tsk);
1041         if (old_mm) {
1042                 up_read(&old_mm->mmap_sem);
1043                 BUG_ON(active_mm != old_mm);
1044                 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
1045                 mm_update_next_owner(old_mm);
1046                 mmput(old_mm);
1047                 return 0;
1048         }
1049         mmdrop(active_mm);
1050         return 0;
1051 }
1052 
1053 /*
1054  * This function makes sure the current process has its own signal table,
1055  * so that flush_signal_handlers can later reset the handlers without
1056  * disturbing other processes.  (Other processes might share the signal
1057  * table via the CLONE_SIGHAND option to clone().)
1058  */
1059 static int de_thread(struct task_struct *tsk)
1060 {
1061         struct signal_struct *sig = tsk->signal;
1062         struct sighand_struct *oldsighand = tsk->sighand;
1063         spinlock_t *lock = &oldsighand->siglock;
1064 
1065         if (thread_group_empty(tsk))
1066                 goto no_thread_group;
1067 
1068         /*
1069          * Kill all other threads in the thread group.
1070          */
1071         spin_lock_irq(lock);
1072         if (signal_group_exit(sig)) {
1073                 /*
1074                  * Another group action in progress, just
1075                  * return so that the signal is processed.
1076                  */
1077                 spin_unlock_irq(lock);
1078                 return -EAGAIN;
1079         }
1080 
1081         sig->group_exit_task = tsk;
1082         sig->notify_count = zap_other_threads(tsk);
1083         if (!thread_group_leader(tsk))
1084                 sig->notify_count--;
1085 
1086         while (sig->notify_count) {
1087                 __set_current_state(TASK_KILLABLE);
1088                 spin_unlock_irq(lock);
1089                 schedule();
1090                 if (__fatal_signal_pending(tsk))
1091                         goto killed;
1092                 spin_lock_irq(lock);
1093         }
1094         spin_unlock_irq(lock);
1095 
1096         /*
1097          * At this point all other threads have exited, all we have to
1098          * do is to wait for the thread group leader to become inactive,
1099          * and to assume its PID:
1100          */
1101         if (!thread_group_leader(tsk)) {
1102                 struct task_struct *leader = tsk->group_leader;
1103 
1104                 for (;;) {
1105                         cgroup_threadgroup_change_begin(tsk);
1106                         write_lock_irq(&tasklist_lock);
1107                         /*
1108                          * Do this under tasklist_lock to ensure that
1109                          * exit_notify() can't miss ->group_exit_task
1110                          */
1111                         sig->notify_count = -1;
1112                         if (likely(leader->exit_state))
1113                                 break;
1114                         __set_current_state(TASK_KILLABLE);
1115                         write_unlock_irq(&tasklist_lock);
1116                         cgroup_threadgroup_change_end(tsk);
1117                         schedule();
1118                         if (__fatal_signal_pending(tsk))
1119                                 goto killed;
1120                 }
1121 
1122                 /*
1123                  * The only record we have of the real-time age of a
1124                  * process, regardless of execs it's done, is start_time.
1125                  * All the past CPU time is accumulated in signal_struct
1126                  * from sister threads now dead.  But in this non-leader
1127                  * exec, nothing survives from the original leader thread,
1128                  * whose birth marks the true age of this process now.
1129                  * When we take on its identity by switching to its PID, we
1130                  * also take its birthdate (always earlier than our own).
1131                  */
1132                 tsk->start_time = leader->start_time;
1133                 tsk->real_start_time = leader->real_start_time;
1134 
1135                 BUG_ON(!same_thread_group(leader, tsk));
1136                 BUG_ON(has_group_leader_pid(tsk));
1137                 /*
1138                  * An exec() starts a new thread group with the
1139                  * TGID of the previous thread group. Rehash the
1140                  * two threads with a switched PID, and release
1141                  * the former thread group leader:
1142                  */
1143 
1144                 /* Become a process group leader with the old leader's pid.
1145                  * The old leader becomes a thread of the this thread group.
1146                  * Note: The old leader also uses this pid until release_task
1147                  *       is called.  Odd but simple and correct.
1148                  */
1149                 tsk->pid = leader->pid;
1150                 change_pid(tsk, PIDTYPE_PID, task_pid(leader));
1151                 transfer_pid(leader, tsk, PIDTYPE_TGID);
1152                 transfer_pid(leader, tsk, PIDTYPE_PGID);
1153                 transfer_pid(leader, tsk, PIDTYPE_SID);
1154 
1155                 list_replace_rcu(&leader->tasks, &tsk->tasks);
1156                 list_replace_init(&leader->sibling, &tsk->sibling);
1157 
1158                 tsk->group_leader = tsk;
1159                 leader->group_leader = tsk;
1160 
1161                 tsk->exit_signal = SIGCHLD;
1162                 leader->exit_signal = -1;
1163 
1164                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1165                 leader->exit_state = EXIT_DEAD;
1166 
1167                 /*
1168                  * We are going to release_task()->ptrace_unlink() silently,
1169                  * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1170                  * the tracer wont't block again waiting for this thread.
1171                  */
1172                 if (unlikely(leader->ptrace))
1173                         __wake_up_parent(leader, leader->parent);
1174                 write_unlock_irq(&tasklist_lock);
1175                 cgroup_threadgroup_change_end(tsk);
1176 
1177                 release_task(leader);
1178         }
1179 
1180         sig->group_exit_task = NULL;
1181         sig->notify_count = 0;
1182 
1183 no_thread_group:
1184         /* we have changed execution domain */
1185         tsk->exit_signal = SIGCHLD;
1186 
1187 #ifdef CONFIG_POSIX_TIMERS
1188         exit_itimers(sig);
1189         flush_itimer_signals();
1190 #endif
1191 
1192         if (refcount_read(&oldsighand->count) != 1) {
1193                 struct sighand_struct *newsighand;
1194                 /*
1195                  * This ->sighand is shared with the CLONE_SIGHAND
1196                  * but not CLONE_THREAD task, switch to the new one.
1197                  */
1198                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1199                 if (!newsighand)
1200                         return -ENOMEM;
1201 
1202                 refcount_set(&newsighand->count, 1);
1203                 memcpy(newsighand->action, oldsighand->action,
1204                        sizeof(newsighand->action));
1205 
1206                 write_lock_irq(&tasklist_lock);
1207                 spin_lock(&oldsighand->siglock);
1208                 rcu_assign_pointer(tsk->sighand, newsighand);
1209                 spin_unlock(&oldsighand->siglock);
1210                 write_unlock_irq(&tasklist_lock);
1211 
1212                 __cleanup_sighand(oldsighand);
1213         }
1214 
1215         BUG_ON(!thread_group_leader(tsk));
1216         return 0;
1217 
1218 killed:
1219         /* protects against exit_notify() and __exit_signal() */
1220         read_lock(&tasklist_lock);
1221         sig->group_exit_task = NULL;
1222         sig->notify_count = 0;
1223         read_unlock(&tasklist_lock);
1224         return -EAGAIN;
1225 }
1226 
1227 char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
1228 {
1229         task_lock(tsk);
1230         strncpy(buf, tsk->comm, buf_size);
1231         task_unlock(tsk);
1232         return buf;
1233 }
1234 EXPORT_SYMBOL_GPL(__get_task_comm);
1235 
1236 /*
1237  * These functions flushes out all traces of the currently running executable
1238  * so that a new one can be started
1239  */
1240 
1241 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1242 {
1243         task_lock(tsk);
1244         trace_task_rename(tsk, buf);
1245         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1246         task_unlock(tsk);
1247         perf_event_comm(tsk, exec);
1248 }
1249 
1250 /*
1251  * Calling this is the point of no return. None of the failures will be
1252  * seen by userspace since either the process is already taking a fatal
1253  * signal (via de_thread() or coredump), or will have SEGV raised
1254  * (after exec_mmap()) by search_binary_handlers (see below).
1255  */
1256 int flush_old_exec(struct linux_binprm * bprm)
1257 {
1258         int retval;
1259 
1260         /*
1261          * Make sure we have a private signal table and that
1262          * we are unassociated from the previous thread group.
1263          */
1264         retval = de_thread(current);
1265         if (retval)
1266                 goto out;
1267 
1268         /*
1269          * Must be called _before_ exec_mmap() as bprm->mm is
1270          * not visibile until then. This also enables the update
1271          * to be lockless.
1272          */
1273         set_mm_exe_file(bprm->mm, bprm->file);
1274 
1275         /*
1276          * Release all of the old mmap stuff
1277          */
1278         acct_arg_size(bprm, 0);
1279         retval = exec_mmap(bprm->mm);
1280         if (retval)
1281                 goto out;
1282 
1283         /*
1284          * After clearing bprm->mm (to mark that current is using the
1285          * prepared mm now), we have nothing left of the original
1286          * process. If anything from here on returns an error, the check
1287          * in search_binary_handler() will SEGV current.
1288          */
1289         bprm->mm = NULL;
1290 
1291         set_fs(USER_DS);
1292         current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
1293                                         PF_NOFREEZE | PF_NO_SETAFFINITY);
1294         flush_thread();
1295         current->personality &= ~bprm->per_clear;
1296 
1297         /*
1298          * We have to apply CLOEXEC before we change whether the process is
1299          * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1300          * trying to access the should-be-closed file descriptors of a process
1301          * undergoing exec(2).
1302          */
1303         do_close_on_exec(current->files);
1304         return 0;
1305 
1306 out:
1307         return retval;
1308 }
1309 EXPORT_SYMBOL(flush_old_exec);
1310 
1311 void would_dump(struct linux_binprm *bprm, struct file *file)
1312 {
1313         struct inode *inode = file_inode(file);
1314         if (inode_permission(inode, MAY_READ) < 0) {
1315                 struct user_namespace *old, *user_ns;
1316                 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1317 
1318                 /* Ensure mm->user_ns contains the executable */
1319                 user_ns = old = bprm->mm->user_ns;
1320                 while ((user_ns != &init_user_ns) &&
1321                        !privileged_wrt_inode_uidgid(user_ns, inode))
1322                         user_ns = user_ns->parent;
1323 
1324                 if (old != user_ns) {
1325                         bprm->mm->user_ns = get_user_ns(user_ns);
1326                         put_user_ns(old);
1327                 }
1328         }
1329 }
1330 EXPORT_SYMBOL(would_dump);
1331 
1332 void setup_new_exec(struct linux_binprm * bprm)
1333 {
1334         /*
1335          * Once here, prepare_binrpm() will not be called any more, so
1336          * the final state of setuid/setgid/fscaps can be merged into the
1337          * secureexec flag.
1338          */
1339         bprm->secureexec |= bprm->cap_elevated;
1340 
1341         if (bprm->secureexec) {
1342                 /* Make sure parent cannot signal privileged process. */
1343                 current->pdeath_signal = 0;
1344 
1345                 /*
1346                  * For secureexec, reset the stack limit to sane default to
1347                  * avoid bad behavior from the prior rlimits. This has to
1348                  * happen before arch_pick_mmap_layout(), which examines
1349                  * RLIMIT_STACK, but after the point of no return to avoid
1350                  * needing to clean up the change on failure.
1351                  */
1352                 if (bprm->rlim_stack.rlim_cur > _STK_LIM)
1353                         bprm->rlim_stack.rlim_cur = _STK_LIM;
1354         }
1355 
1356         arch_pick_mmap_layout(current->mm, &bprm->rlim_stack);
1357 
1358         current->sas_ss_sp = current->sas_ss_size = 0;
1359 
1360         /*
1361          * Figure out dumpability. Note that this checking only of current
1362          * is wrong, but userspace depends on it. This should be testing
1363          * bprm->secureexec instead.
1364          */
1365         if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
1366             !(uid_eq(current_euid(), current_uid()) &&
1367               gid_eq(current_egid(), current_gid())))
1368                 set_dumpable(current->mm, suid_dumpable);
1369         else
1370                 set_dumpable(current->mm, SUID_DUMP_USER);
1371 
1372         arch_setup_new_exec();
1373         perf_event_exec();
1374         __set_task_comm(current, kbasename(bprm->filename), true);
1375 
1376         /* Set the new mm task size. We have to do that late because it may
1377          * depend on TIF_32BIT which is only updated in flush_thread() on
1378          * some architectures like powerpc
1379          */
1380         current->mm->task_size = TASK_SIZE;
1381 
1382         /* An exec changes our domain. We are no longer part of the thread
1383            group */
1384         current->self_exec_id++;
1385         flush_signal_handlers(current, 0);
1386 }
1387 EXPORT_SYMBOL(setup_new_exec);
1388 
1389 /* Runs immediately before start_thread() takes over. */
1390 void finalize_exec(struct linux_binprm *bprm)
1391 {
1392         /* Store any stack rlimit changes before starting thread. */
1393         task_lock(current->group_leader);
1394         current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack;
1395         task_unlock(current->group_leader);
1396 }
1397 EXPORT_SYMBOL(finalize_exec);
1398 
1399 /*
1400  * Prepare credentials and lock ->cred_guard_mutex.
1401  * install_exec_creds() commits the new creds and drops the lock.
1402  * Or, if exec fails before, free_bprm() should release ->cred and
1403  * and unlock.
1404  */
1405 static int prepare_bprm_creds(struct linux_binprm *bprm)
1406 {
1407         if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1408                 return -ERESTARTNOINTR;
1409 
1410         bprm->cred = prepare_exec_creds();
1411         if (likely(bprm->cred))
1412                 return 0;
1413 
1414         mutex_unlock(&current->signal->cred_guard_mutex);
1415         return -ENOMEM;
1416 }
1417 
1418 static void free_bprm(struct linux_binprm *bprm)
1419 {
1420         free_arg_pages(bprm);
1421         if (bprm->cred) {
1422                 mutex_unlock(&current->signal->cred_guard_mutex);
1423                 abort_creds(bprm->cred);
1424         }
1425         if (bprm->file) {
1426                 allow_write_access(bprm->file);
1427                 fput(bprm->file);
1428         }
1429         /* If a binfmt changed the interp, free it. */
1430         if (bprm->interp != bprm->filename)
1431                 kfree(bprm->interp);
1432         kfree(bprm);
1433 }
1434 
1435 int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
1436 {
1437         /* If a binfmt changed the interp, free it first. */
1438         if (bprm->interp != bprm->filename)
1439                 kfree(bprm->interp);
1440         bprm->interp = kstrdup(interp, GFP_KERNEL);
1441         if (!bprm->interp)
1442                 return -ENOMEM;
1443         return 0;
1444 }
1445 EXPORT_SYMBOL(bprm_change_interp);
1446 
1447 /*
1448  * install the new credentials for this executable
1449  */
1450 void install_exec_creds(struct linux_binprm *bprm)
1451 {
1452         security_bprm_committing_creds(bprm);
1453 
1454         commit_creds(bprm->cred);
1455         bprm->cred = NULL;
1456 
1457         /*
1458          * Disable monitoring for regular users
1459          * when executing setuid binaries. Must
1460          * wait until new credentials are committed
1461          * by commit_creds() above
1462          */
1463         if (get_dumpable(current->mm) != SUID_DUMP_USER)
1464                 perf_event_exit_task(current);
1465         /*
1466          * cred_guard_mutex must be held at least to this point to prevent
1467          * ptrace_attach() from altering our determination of the task's
1468          * credentials; any time after this it may be unlocked.
1469          */
1470         security_bprm_committed_creds(bprm);
1471         mutex_unlock(&current->signal->cred_guard_mutex);
1472 }
1473 EXPORT_SYMBOL(install_exec_creds);
1474 
1475 /*
1476  * determine how safe it is to execute the proposed program
1477  * - the caller must hold ->cred_guard_mutex to protect against
1478  *   PTRACE_ATTACH or seccomp thread-sync
1479  */
1480 static void check_unsafe_exec(struct linux_binprm *bprm)
1481 {
1482         struct task_struct *p = current, *t;
1483         unsigned n_fs;
1484 
1485         if (p->ptrace)
1486                 bprm->unsafe |= LSM_UNSAFE_PTRACE;
1487 
1488         /*
1489          * This isn't strictly necessary, but it makes it harder for LSMs to
1490          * mess up.
1491          */
1492         if (task_no_new_privs(current))
1493                 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1494 
1495         t = p;
1496         n_fs = 1;
1497         spin_lock(&p->fs->lock);
1498         rcu_read_lock();
1499         while_each_thread(p, t) {
1500                 if (t->fs == p->fs)
1501                         n_fs++;
1502         }
1503         rcu_read_unlock();
1504 
1505         if (p->fs->users > n_fs)
1506                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1507         else
1508                 p->fs->in_exec = 1;
1509         spin_unlock(&p->fs->lock);
1510 }
1511 
1512 static void bprm_fill_uid(struct linux_binprm *bprm)
1513 {
1514         struct inode *inode;
1515         unsigned int mode;
1516         kuid_t uid;
1517         kgid_t gid;
1518 
1519         /*
1520          * Since this can be called multiple times (via prepare_binprm),
1521          * we must clear any previous work done when setting set[ug]id
1522          * bits from any earlier bprm->file uses (for example when run
1523          * first for a setuid script then again for its interpreter).
1524          */
1525         bprm->cred->euid = current_euid();
1526         bprm->cred->egid = current_egid();
1527 
1528         if (!mnt_may_suid(bprm->file->f_path.mnt))
1529                 return;
1530 
1531         if (task_no_new_privs(current))
1532                 return;
1533 
1534         inode = bprm->file->f_path.dentry->d_inode;
1535         mode = READ_ONCE(inode->i_mode);
1536         if (!(mode & (S_ISUID|S_ISGID)))
1537                 return;
1538 
1539         /* Be careful if suid/sgid is set */
1540         inode_lock(inode);
1541 
1542         /* reload atomically mode/uid/gid now that lock held */
1543         mode = inode->i_mode;
1544         uid = inode->i_uid;
1545         gid = inode->i_gid;
1546         inode_unlock(inode);
1547 
1548         /* We ignore suid/sgid if there are no mappings for them in the ns */
1549         if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
1550                  !kgid_has_mapping(bprm->cred->user_ns, gid))
1551                 return;
1552 
1553         if (mode & S_ISUID) {
1554                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1555                 bprm->cred->euid = uid;
1556         }
1557 
1558         if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1559                 bprm->per_clear |= PER_CLEAR_ON_SETID;
1560                 bprm->cred->egid = gid;
1561         }
1562 }
1563 
1564 /*
1565  * Fill the binprm structure from the inode.
1566  * Check permissions, then read the first BINPRM_BUF_SIZE bytes
1567  *
1568  * This may be called multiple times for binary chains (scripts for example).
1569  */
1570 int prepare_binprm(struct linux_binprm *bprm)
1571 {
1572         int retval;
1573         loff_t pos = 0;
1574 
1575         bprm_fill_uid(bprm);
1576 
1577         /* fill in binprm security blob */
1578         retval = security_bprm_set_creds(bprm);
1579         if (retval)
1580                 return retval;
1581         bprm->called_set_creds = 1;
1582 
1583         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1584         return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
1585 }
1586 
1587 EXPORT_SYMBOL(prepare_binprm);
1588 
1589 /*
1590  * Arguments are '\0' separated strings found at the location bprm->p
1591  * points to; chop off the first by relocating brpm->p to right after
1592  * the first '\0' encountered.
1593  */
1594 int remove_arg_zero(struct linux_binprm *bprm)
1595 {
1596         int ret = 0;
1597         unsigned long offset;
1598         char *kaddr;
1599         struct page *page;
1600 
1601         if (!bprm->argc)
1602                 return 0;
1603 
1604         do {
1605                 offset = bprm->p & ~PAGE_MASK;
1606                 page = get_arg_page(bprm, bprm->p, 0);
1607                 if (!page) {
1608                         ret = -EFAULT;
1609                         goto out;
1610                 }
1611                 kaddr = kmap_atomic(page);
1612 
1613                 for (; offset < PAGE_SIZE && kaddr[offset];
1614                                 offset++, bprm->p++)
1615                         ;
1616 
1617                 kunmap_atomic(kaddr);
1618                 put_arg_page(page);
1619         } while (offset == PAGE_SIZE);
1620 
1621         bprm->p++;
1622         bprm->argc--;
1623         ret = 0;
1624 
1625 out:
1626         return ret;
1627 }
1628 EXPORT_SYMBOL(remove_arg_zero);
1629 
1630 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1631 /*
1632  * cycle the list of binary formats handler, until one recognizes the image
1633  */
1634 int search_binary_handler(struct linux_binprm *bprm)
1635 {
1636         bool need_retry = IS_ENABLED(CONFIG_MODULES);
1637         struct linux_binfmt *fmt;
1638         int retval;
1639 
1640         /* This allows 4 levels of binfmt rewrites before failing hard. */
1641         if (bprm->recursion_depth > 5)
1642                 return -ELOOP;
1643 
1644         retval = security_bprm_check(bprm);
1645         if (retval)
1646                 return retval;
1647 
1648         retval = -ENOENT;
1649  retry:
1650         read_lock(&binfmt_lock);
1651         list_for_each_entry(fmt, &formats, lh) {
1652                 if (!try_module_get(fmt->module))
1653                         continue;
1654                 read_unlock(&binfmt_lock);
1655                 bprm->recursion_depth++;
1656                 retval = fmt->load_binary(bprm);
1657                 read_lock(&binfmt_lock);
1658                 put_binfmt(fmt);
1659                 bprm->recursion_depth--;
1660                 if (retval < 0 && !bprm->mm) {
1661                         /* we got to flush_old_exec() and failed after it */
1662                         read_unlock(&binfmt_lock);
1663                         force_sigsegv(SIGSEGV, current);
1664                         return retval;
1665                 }
1666                 if (retval != -ENOEXEC || !bprm->file) {
1667                         read_unlock(&binfmt_lock);
1668                         return retval;
1669                 }
1670         }
1671         read_unlock(&binfmt_lock);
1672 
1673         if (need_retry) {
1674                 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1675                     printable(bprm->buf[2]) && printable(bprm->buf[3]))
1676                         return retval;
1677                 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1678                         return retval;
1679                 need_retry = false;
1680                 goto retry;
1681         }
1682 
1683         return retval;
1684 }
1685 EXPORT_SYMBOL(search_binary_handler);
1686 
1687 static int exec_binprm(struct linux_binprm *bprm)
1688 {
1689         pid_t old_pid, old_vpid;
1690         int ret;
1691 
1692         /* Need to fetch pid before load_binary changes it */
1693         old_pid = current->pid;
1694         rcu_read_lock();
1695         old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1696         rcu_read_unlock();
1697 
1698         ret = ccs_search_binary_handler(bprm);
1699         if (ret >= 0) {
1700                 audit_bprm(bprm);
1701                 trace_sched_process_exec(current, old_pid, bprm);
1702                 ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1703                 proc_exec_connector(current);
1704         }
1705 
1706         return ret;
1707 }
1708 
1709 /*
1710  * sys_execve() executes a new program.
1711  */
1712 static int __do_execve_file(int fd, struct filename *filename,
1713                             struct user_arg_ptr argv,
1714                             struct user_arg_ptr envp,
1715                             int flags, struct file *file)
1716 {
1717         char *pathbuf = NULL;
1718         struct linux_binprm *bprm;
1719         struct files_struct *displaced;
1720         int retval;
1721 
1722         if (IS_ERR(filename))
1723                 return PTR_ERR(filename);
1724 
1725         /*
1726          * We move the actual failure in case of RLIMIT_NPROC excess from
1727          * set*uid() to execve() because too many poorly written programs
1728          * don't check setuid() return code.  Here we additionally recheck
1729          * whether NPROC limit is still exceeded.
1730          */
1731         if ((current->flags & PF_NPROC_EXCEEDED) &&
1732             atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
1733                 retval = -EAGAIN;
1734                 goto out_ret;
1735         }
1736 
1737         /* We're below the limit (still or again), so we don't want to make
1738          * further execve() calls fail. */
1739         current->flags &= ~PF_NPROC_EXCEEDED;
1740 
1741         retval = unshare_files(&displaced);
1742         if (retval)
1743                 goto out_ret;
1744 
1745         retval = -ENOMEM;
1746         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1747         if (!bprm)
1748                 goto out_files;
1749 
1750         retval = prepare_bprm_creds(bprm);
1751         if (retval)
1752                 goto out_free;
1753 
1754         check_unsafe_exec(bprm);
1755         current->in_execve = 1;
1756 
1757         if (!file)
1758                 file = do_open_execat(fd, filename, flags);
1759         retval = PTR_ERR(file);
1760         if (IS_ERR(file))
1761                 goto out_unmark;
1762 
1763         sched_exec();
1764 
1765         bprm->file = file;
1766         if (!filename) {
1767                 bprm->filename = "none";
1768         } else if (fd == AT_FDCWD || filename->name[0] == '/') {
1769                 bprm->filename = filename->name;
1770         } else {
1771                 if (filename->name[0] == '\0')
1772                         pathbuf = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd);
1773                 else
1774                         pathbuf = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s",
1775                                             fd, filename->name);
1776                 if (!pathbuf) {
1777                         retval = -ENOMEM;
1778                         goto out_unmark;
1779                 }
1780                 /*
1781                  * Record that a name derived from an O_CLOEXEC fd will be
1782                  * inaccessible after exec. Relies on having exclusive access to
1783                  * current->files (due to unshare_files above).
1784                  */
1785                 if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt)))
1786                         bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1787                 bprm->filename = pathbuf;
1788         }
1789         bprm->interp = bprm->filename;
1790 
1791         retval = bprm_mm_init(bprm);
1792         if (retval)
1793                 goto out_unmark;
1794 
1795         retval = prepare_arg_pages(bprm, argv, envp);
1796         if (retval < 0)
1797                 goto out;
1798 
1799         retval = prepare_binprm(bprm);
1800         if (retval < 0)
1801                 goto out;
1802 
1803         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1804         if (retval < 0)
1805                 goto out;
1806 
1807         bprm->exec = bprm->p;
1808         retval = copy_strings(bprm->envc, envp, bprm);
1809         if (retval < 0)
1810                 goto out;
1811 
1812         retval = copy_strings(bprm->argc, argv, bprm);
1813         if (retval < 0)
1814                 goto out;
1815 
1816         would_dump(bprm, bprm->file);
1817 
1818         retval = exec_binprm(bprm);
1819         if (retval < 0)
1820                 goto out;
1821 
1822         /* execve succeeded */
1823         current->fs->in_exec = 0;
1824         current->in_execve = 0;
1825         membarrier_execve(current);
1826         rseq_execve(current);
1827         acct_update_integrals(current);
1828         task_numa_free(current);
1829         free_bprm(bprm);
1830         kfree(pathbuf);
1831         if (filename)
1832                 putname(filename);
1833         if (displaced)
1834                 put_files_struct(displaced);
1835         return retval;
1836 
1837 out:
1838         if (bprm->mm) {
1839                 acct_arg_size(bprm, 0);
1840                 mmput(bprm->mm);
1841         }
1842 
1843 out_unmark:
1844         current->fs->in_exec = 0;
1845         current->in_execve = 0;
1846 
1847 out_free:
1848         free_bprm(bprm);
1849         kfree(pathbuf);
1850 
1851 out_files:
1852         if (displaced)
1853                 reset_files_struct(displaced);
1854 out_ret:
1855         if (filename)
1856                 putname(filename);
1857         return retval;
1858 }
1859 
1860 static int do_execveat_common(int fd, struct filename *filename,
1861                               struct user_arg_ptr argv,
1862                               struct user_arg_ptr envp,
1863                               int flags)
1864 {
1865         return __do_execve_file(fd, filename, argv, envp, flags, NULL);
1866 }
1867 
1868 int do_execve_file(struct file *file, void *__argv, void *__envp)
1869 {
1870         struct user_arg_ptr argv = { .ptr.native = __argv };
1871         struct user_arg_ptr envp = { .ptr.native = __envp };
1872 
1873         return __do_execve_file(AT_FDCWD, NULL, argv, envp, 0, file);
1874 }
1875 
1876 int do_execve(struct filename *filename,
1877         const char __user *const __user *__argv,
1878         const char __user *const __user *__envp)
1879 {
1880         struct user_arg_ptr argv = { .ptr.native = __argv };
1881         struct user_arg_ptr envp = { .ptr.native = __envp };
1882         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1883 }
1884 
1885 int do_execveat(int fd, struct filename *filename,
1886                 const char __user *const __user *__argv,
1887                 const char __user *const __user *__envp,
1888                 int flags)
1889 {
1890         struct user_arg_ptr argv = { .ptr.native = __argv };
1891         struct user_arg_ptr envp = { .ptr.native = __envp };
1892 
1893         return do_execveat_common(fd, filename, argv, envp, flags);
1894 }
1895 
1896 #ifdef CONFIG_COMPAT
1897 static int compat_do_execve(struct filename *filename,
1898         const compat_uptr_t __user *__argv,
1899         const compat_uptr_t __user *__envp)
1900 {
1901         struct user_arg_ptr argv = {
1902                 .is_compat = true,
1903                 .ptr.compat = __argv,
1904         };
1905         struct user_arg_ptr envp = {
1906                 .is_compat = true,
1907                 .ptr.compat = __envp,
1908         };
1909         return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1910 }
1911 
1912 static int compat_do_execveat(int fd, struct filename *filename,
1913                               const compat_uptr_t __user *__argv,
1914                               const compat_uptr_t __user *__envp,
1915                               int flags)
1916 {
1917         struct user_arg_ptr argv = {
1918                 .is_compat = true,
1919                 .ptr.compat = __argv,
1920         };
1921         struct user_arg_ptr envp = {
1922                 .is_compat = true,
1923                 .ptr.compat = __envp,
1924         };
1925         return do_execveat_common(fd, filename, argv, envp, flags);
1926 }
1927 #endif
1928 
1929 void set_binfmt(struct linux_binfmt *new)
1930 {
1931         struct mm_struct *mm = current->mm;
1932 
1933         if (mm->binfmt)
1934                 module_put(mm->binfmt->module);
1935 
1936         mm->binfmt = new;
1937         if (new)
1938                 __module_get(new->module);
1939 }
1940 EXPORT_SYMBOL(set_binfmt);
1941 
1942 /*
1943  * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
1944  */
1945 void set_dumpable(struct mm_struct *mm, int value)
1946 {
1947         if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
1948                 return;
1949 
1950         set_mask_bits(&mm->flags, MMF_DUMPABLE_MASK, value);
1951 }
1952 
1953 SYSCALL_DEFINE3(execve,
1954                 const char __user *, filename,
1955                 const char __user *const __user *, argv,
1956                 const char __user *const __user *, envp)
1957 {
1958         return do_execve(getname(filename), argv, envp);
1959 }
1960 
1961 SYSCALL_DEFINE5(execveat,
1962                 int, fd, const char __user *, filename,
1963                 const char __user *const __user *, argv,
1964                 const char __user *const __user *, envp,
1965                 int, flags)
1966 {
1967         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1968 
1969         return do_execveat(fd,
1970                            getname_flags(filename, lookup_flags, NULL),
1971                            argv, envp, flags);
1972 }
1973 
1974 #ifdef CONFIG_COMPAT
1975 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
1976         const compat_uptr_t __user *, argv,
1977         const compat_uptr_t __user *, envp)
1978 {
1979         return compat_do_execve(getname(filename), argv, envp);
1980 }
1981 
1982 COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
1983                        const char __user *, filename,
1984                        const compat_uptr_t __user *, argv,
1985                        const compat_uptr_t __user *, envp,
1986                        int,  flags)
1987 {
1988         int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1989 
1990         return compat_do_execveat(fd,
1991                                   getname_flags(filename, lookup_flags, NULL),
1992                                   argv, envp, flags);
1993 }
1994 #endif
1995 

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