xref: /linux/fs/exec.c (revision 42b16d3ac371a2fac9b6f08fd75f23f34ba3955a)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  linux/fs/exec.c
4  *
5  *  Copyright (C) 1991, 1992  Linus Torvalds
6  */
7 
8 /*
9  * #!-checking implemented by tytso.
10  */
11 /*
12  * Demand-loading implemented 01.12.91 - no need to read anything but
13  * the header into memory. The inode of the executable is put into
14  * "current->executable", and page faults do the actual loading. Clean.
15  *
16  * Once more I can proudly say that linux stood up to being changed: it
17  * was less than 2 hours work to get demand-loading completely implemented.
18  *
19  * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
20  * current->executable is only used by the procfs.  This allows a dispatch
21  * table to check for several different types  of binary formats.  We keep
22  * trying until we recognize the file or we run out of supported binary
23  * formats.
24  */
25 
26 #include <linux/kernel_read_file.h>
27 #include <linux/slab.h>
28 #include <linux/file.h>
29 #include <linux/fdtable.h>
30 #include <linux/mm.h>
31 #include <linux/stat.h>
32 #include <linux/fcntl.h>
33 #include <linux/swap.h>
34 #include <linux/string.h>
35 #include <linux/init.h>
36 #include <linux/sched/mm.h>
37 #include <linux/sched/coredump.h>
38 #include <linux/sched/signal.h>
39 #include <linux/sched/numa_balancing.h>
40 #include <linux/sched/task.h>
41 #include <linux/pagemap.h>
42 #include <linux/perf_event.h>
43 #include <linux/highmem.h>
44 #include <linux/spinlock.h>
45 #include <linux/key.h>
46 #include <linux/personality.h>
47 #include <linux/binfmts.h>
48 #include <linux/utsname.h>
49 #include <linux/pid_namespace.h>
50 #include <linux/module.h>
51 #include <linux/namei.h>
52 #include <linux/mount.h>
53 #include <linux/security.h>
54 #include <linux/syscalls.h>
55 #include <linux/tsacct_kern.h>
56 #include <linux/cn_proc.h>
57 #include <linux/audit.h>
58 #include <linux/kmod.h>
59 #include <linux/fsnotify.h>
60 #include <linux/fs_struct.h>
61 #include <linux/oom.h>
62 #include <linux/compat.h>
63 #include <linux/vmalloc.h>
64 #include <linux/io_uring.h>
65 #include <linux/syscall_user_dispatch.h>
66 #include <linux/coredump.h>
67 #include <linux/time_namespace.h>
68 #include <linux/user_events.h>
69 #include <linux/rseq.h>
70 #include <linux/ksm.h>
71 
72 #include <linux/uaccess.h>
73 #include <asm/mmu_context.h>
74 #include <asm/tlb.h>
75 
76 #include <trace/events/task.h>
77 #include "internal.h"
78 
79 #include <trace/events/sched.h>
80 
81 static int bprm_creds_from_file(struct linux_binprm *bprm);
82 
83 int suid_dumpable = 0;
84 
85 static LIST_HEAD(formats);
86 static DEFINE_RWLOCK(binfmt_lock);
87 
__register_binfmt(struct linux_binfmt * fmt,int insert)88 void __register_binfmt(struct linux_binfmt * fmt, int insert)
89 {
90 	write_lock(&binfmt_lock);
91 	insert ? list_add(&fmt->lh, &formats) :
92 		 list_add_tail(&fmt->lh, &formats);
93 	write_unlock(&binfmt_lock);
94 }
95 
96 EXPORT_SYMBOL(__register_binfmt);
97 
unregister_binfmt(struct linux_binfmt * fmt)98 void unregister_binfmt(struct linux_binfmt * fmt)
99 {
100 	write_lock(&binfmt_lock);
101 	list_del(&fmt->lh);
102 	write_unlock(&binfmt_lock);
103 }
104 
105 EXPORT_SYMBOL(unregister_binfmt);
106 
put_binfmt(struct linux_binfmt * fmt)107 static inline void put_binfmt(struct linux_binfmt * fmt)
108 {
109 	module_put(fmt->module);
110 }
111 
path_noexec(const struct path * path)112 bool path_noexec(const struct path *path)
113 {
114 	return (path->mnt->mnt_flags & MNT_NOEXEC) ||
115 	       (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
116 }
117 
118 #ifdef CONFIG_USELIB
119 /*
120  * Note that a shared library must be both readable and executable due to
121  * security reasons.
122  *
123  * Also note that we take the address to load from the file itself.
124  */
SYSCALL_DEFINE1(uselib,const char __user *,library)125 SYSCALL_DEFINE1(uselib, const char __user *, library)
126 {
127 	struct linux_binfmt *fmt;
128 	struct file *file;
129 	struct filename *tmp = getname(library);
130 	int error = PTR_ERR(tmp);
131 	static const struct open_flags uselib_flags = {
132 		.open_flag = O_LARGEFILE | O_RDONLY,
133 		.acc_mode = MAY_READ | MAY_EXEC,
134 		.intent = LOOKUP_OPEN,
135 		.lookup_flags = LOOKUP_FOLLOW,
136 	};
137 
138 	if (IS_ERR(tmp))
139 		goto out;
140 
141 	file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
142 	putname(tmp);
143 	error = PTR_ERR(file);
144 	if (IS_ERR(file))
145 		goto out;
146 
147 	/*
148 	 * Check do_open_execat() for an explanation.
149 	 */
150 	error = -EACCES;
151 	if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode)) ||
152 	    path_noexec(&file->f_path))
153 		goto exit;
154 
155 	error = -ENOEXEC;
156 
157 	read_lock(&binfmt_lock);
158 	list_for_each_entry(fmt, &formats, lh) {
159 		if (!fmt->load_shlib)
160 			continue;
161 		if (!try_module_get(fmt->module))
162 			continue;
163 		read_unlock(&binfmt_lock);
164 		error = fmt->load_shlib(file);
165 		read_lock(&binfmt_lock);
166 		put_binfmt(fmt);
167 		if (error != -ENOEXEC)
168 			break;
169 	}
170 	read_unlock(&binfmt_lock);
171 exit:
172 	fput(file);
173 out:
174 	return error;
175 }
176 #endif /* #ifdef CONFIG_USELIB */
177 
178 #ifdef CONFIG_MMU
179 /*
180  * The nascent bprm->mm is not visible until exec_mmap() but it can
181  * use a lot of memory, account these pages in current->mm temporary
182  * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
183  * change the counter back via acct_arg_size(0).
184  */
acct_arg_size(struct linux_binprm * bprm,unsigned long pages)185 static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
186 {
187 	struct mm_struct *mm = current->mm;
188 	long diff = (long)(pages - bprm->vma_pages);
189 
190 	if (!mm || !diff)
191 		return;
192 
193 	bprm->vma_pages = pages;
194 	add_mm_counter(mm, MM_ANONPAGES, diff);
195 }
196 
get_arg_page(struct linux_binprm * bprm,unsigned long pos,int write)197 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
198 		int write)
199 {
200 	struct page *page;
201 	struct vm_area_struct *vma = bprm->vma;
202 	struct mm_struct *mm = bprm->mm;
203 	int ret;
204 
205 	/*
206 	 * Avoid relying on expanding the stack down in GUP (which
207 	 * does not work for STACK_GROWSUP anyway), and just do it
208 	 * by hand ahead of time.
209 	 */
210 	if (write && pos < vma->vm_start) {
211 		mmap_write_lock(mm);
212 		ret = expand_downwards(vma, pos);
213 		if (unlikely(ret < 0)) {
214 			mmap_write_unlock(mm);
215 			return NULL;
216 		}
217 		mmap_write_downgrade(mm);
218 	} else
219 		mmap_read_lock(mm);
220 
221 	/*
222 	 * We are doing an exec().  'current' is the process
223 	 * doing the exec and 'mm' is the new process's mm.
224 	 */
225 	ret = get_user_pages_remote(mm, pos, 1,
226 			write ? FOLL_WRITE : 0,
227 			&page, NULL);
228 	mmap_read_unlock(mm);
229 	if (ret <= 0)
230 		return NULL;
231 
232 	if (write)
233 		acct_arg_size(bprm, vma_pages(vma));
234 
235 	return page;
236 }
237 
put_arg_page(struct page * page)238 static void put_arg_page(struct page *page)
239 {
240 	put_page(page);
241 }
242 
free_arg_pages(struct linux_binprm * bprm)243 static void free_arg_pages(struct linux_binprm *bprm)
244 {
245 }
246 
flush_arg_page(struct linux_binprm * bprm,unsigned long pos,struct page * page)247 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
248 		struct page *page)
249 {
250 	flush_cache_page(bprm->vma, pos, page_to_pfn(page));
251 }
252 
__bprm_mm_init(struct linux_binprm * bprm)253 static int __bprm_mm_init(struct linux_binprm *bprm)
254 {
255 	int err;
256 	struct vm_area_struct *vma = NULL;
257 	struct mm_struct *mm = bprm->mm;
258 
259 	bprm->vma = vma = vm_area_alloc(mm);
260 	if (!vma)
261 		return -ENOMEM;
262 	vma_set_anonymous(vma);
263 
264 	if (mmap_write_lock_killable(mm)) {
265 		err = -EINTR;
266 		goto err_free;
267 	}
268 
269 	/*
270 	 * Need to be called with mmap write lock
271 	 * held, to avoid race with ksmd.
272 	 */
273 	err = ksm_execve(mm);
274 	if (err)
275 		goto err_ksm;
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 	vm_flags_init(vma, VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP);
287 	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
288 
289 	err = insert_vm_struct(mm, vma);
290 	if (err)
291 		goto err;
292 
293 	mm->stack_vm = mm->total_vm = 1;
294 	mmap_write_unlock(mm);
295 	bprm->p = vma->vm_end - sizeof(void *);
296 	return 0;
297 err:
298 	ksm_exit(mm);
299 err_ksm:
300 	mmap_write_unlock(mm);
301 err_free:
302 	bprm->vma = NULL;
303 	vm_area_free(vma);
304 	return err;
305 }
306 
valid_arg_len(struct linux_binprm * bprm,long len)307 static bool valid_arg_len(struct linux_binprm *bprm, long len)
308 {
309 	return len <= MAX_ARG_STRLEN;
310 }
311 
312 #else
313 
acct_arg_size(struct linux_binprm * bprm,unsigned long pages)314 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
315 {
316 }
317 
get_arg_page(struct linux_binprm * bprm,unsigned long pos,int write)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 
put_arg_page(struct page * page)334 static void put_arg_page(struct page *page)
335 {
336 }
337 
free_arg_page(struct linux_binprm * bprm,int i)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 
free_arg_pages(struct linux_binprm * bprm)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 
flush_arg_page(struct linux_binprm * bprm,unsigned long pos,struct page * page)354 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
355 		struct page *page)
356 {
357 }
358 
__bprm_mm_init(struct linux_binprm * bprm)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 
valid_arg_len(struct linux_binprm * bprm,long len)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  */
bprm_mm_init(struct linux_binprm * bprm)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 	/* Save current stack limit for all calculations made during exec. */
389 	task_lock(current->group_leader);
390 	bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK];
391 	task_unlock(current->group_leader);
392 
393 	err = __bprm_mm_init(bprm);
394 	if (err)
395 		goto err;
396 
397 	return 0;
398 
399 err:
400 	if (mm) {
401 		bprm->mm = NULL;
402 		mmdrop(mm);
403 	}
404 
405 	return err;
406 }
407 
408 struct user_arg_ptr {
409 #ifdef CONFIG_COMPAT
410 	bool is_compat;
411 #endif
412 	union {
413 		const char __user *const __user *native;
414 #ifdef CONFIG_COMPAT
415 		const compat_uptr_t __user *compat;
416 #endif
417 	} ptr;
418 };
419 
get_user_arg_ptr(struct user_arg_ptr argv,int nr)420 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
421 {
422 	const char __user *native;
423 
424 #ifdef CONFIG_COMPAT
425 	if (unlikely(argv.is_compat)) {
426 		compat_uptr_t compat;
427 
428 		if (get_user(compat, argv.ptr.compat + nr))
429 			return ERR_PTR(-EFAULT);
430 
431 		return compat_ptr(compat);
432 	}
433 #endif
434 
435 	if (get_user(native, argv.ptr.native + nr))
436 		return ERR_PTR(-EFAULT);
437 
438 	return native;
439 }
440 
441 /*
442  * count() counts the number of strings in array ARGV.
443  */
count(struct user_arg_ptr argv,int max)444 static int count(struct user_arg_ptr argv, int max)
445 {
446 	int i = 0;
447 
448 	if (argv.ptr.native != NULL) {
449 		for (;;) {
450 			const char __user *p = get_user_arg_ptr(argv, i);
451 
452 			if (!p)
453 				break;
454 
455 			if (IS_ERR(p))
456 				return -EFAULT;
457 
458 			if (i >= max)
459 				return -E2BIG;
460 			++i;
461 
462 			if (fatal_signal_pending(current))
463 				return -ERESTARTNOHAND;
464 			cond_resched();
465 		}
466 	}
467 	return i;
468 }
469 
count_strings_kernel(const char * const * argv)470 static int count_strings_kernel(const char *const *argv)
471 {
472 	int i;
473 
474 	if (!argv)
475 		return 0;
476 
477 	for (i = 0; argv[i]; ++i) {
478 		if (i >= MAX_ARG_STRINGS)
479 			return -E2BIG;
480 		if (fatal_signal_pending(current))
481 			return -ERESTARTNOHAND;
482 		cond_resched();
483 	}
484 	return i;
485 }
486 
bprm_set_stack_limit(struct linux_binprm * bprm,unsigned long limit)487 static inline int bprm_set_stack_limit(struct linux_binprm *bprm,
488 				       unsigned long limit)
489 {
490 #ifdef CONFIG_MMU
491 	/* Avoid a pathological bprm->p. */
492 	if (bprm->p < limit)
493 		return -E2BIG;
494 	bprm->argmin = bprm->p - limit;
495 #endif
496 	return 0;
497 }
bprm_hit_stack_limit(struct linux_binprm * bprm)498 static inline bool bprm_hit_stack_limit(struct linux_binprm *bprm)
499 {
500 #ifdef CONFIG_MMU
501 	return bprm->p < bprm->argmin;
502 #else
503 	return false;
504 #endif
505 }
506 
507 /*
508  * Calculate bprm->argmin from:
509  * - _STK_LIM
510  * - ARG_MAX
511  * - bprm->rlim_stack.rlim_cur
512  * - bprm->argc
513  * - bprm->envc
514  * - bprm->p
515  */
bprm_stack_limits(struct linux_binprm * bprm)516 static int bprm_stack_limits(struct linux_binprm *bprm)
517 {
518 	unsigned long limit, ptr_size;
519 
520 	/*
521 	 * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
522 	 * (whichever is smaller) for the argv+env strings.
523 	 * This ensures that:
524 	 *  - the remaining binfmt code will not run out of stack space,
525 	 *  - the program will have a reasonable amount of stack left
526 	 *    to work from.
527 	 */
528 	limit = _STK_LIM / 4 * 3;
529 	limit = min(limit, bprm->rlim_stack.rlim_cur / 4);
530 	/*
531 	 * We've historically supported up to 32 pages (ARG_MAX)
532 	 * of argument strings even with small stacks
533 	 */
534 	limit = max_t(unsigned long, limit, ARG_MAX);
535 	/* Reject totally pathological counts. */
536 	if (bprm->argc < 0 || bprm->envc < 0)
537 		return -E2BIG;
538 	/*
539 	 * We must account for the size of all the argv and envp pointers to
540 	 * the argv and envp strings, since they will also take up space in
541 	 * the stack. They aren't stored until much later when we can't
542 	 * signal to the parent that the child has run out of stack space.
543 	 * Instead, calculate it here so it's possible to fail gracefully.
544 	 *
545 	 * In the case of argc = 0, make sure there is space for adding a
546 	 * empty string (which will bump argc to 1), to ensure confused
547 	 * userspace programs don't start processing from argv[1], thinking
548 	 * argc can never be 0, to keep them from walking envp by accident.
549 	 * See do_execveat_common().
550 	 */
551 	if (check_add_overflow(max(bprm->argc, 1), bprm->envc, &ptr_size) ||
552 	    check_mul_overflow(ptr_size, sizeof(void *), &ptr_size))
553 		return -E2BIG;
554 	if (limit <= ptr_size)
555 		return -E2BIG;
556 	limit -= ptr_size;
557 
558 	return bprm_set_stack_limit(bprm, limit);
559 }
560 
561 /*
562  * 'copy_strings()' copies argument/environment strings from the old
563  * processes's memory to the new process's stack.  The call to get_user_pages()
564  * ensures the destination page is created and not swapped out.
565  */
copy_strings(int argc,struct user_arg_ptr argv,struct linux_binprm * bprm)566 static int copy_strings(int argc, struct user_arg_ptr argv,
567 			struct linux_binprm *bprm)
568 {
569 	struct page *kmapped_page = NULL;
570 	char *kaddr = NULL;
571 	unsigned long kpos = 0;
572 	int ret;
573 
574 	while (argc-- > 0) {
575 		const char __user *str;
576 		int len;
577 		unsigned long pos;
578 
579 		ret = -EFAULT;
580 		str = get_user_arg_ptr(argv, argc);
581 		if (IS_ERR(str))
582 			goto out;
583 
584 		len = strnlen_user(str, MAX_ARG_STRLEN);
585 		if (!len)
586 			goto out;
587 
588 		ret = -E2BIG;
589 		if (!valid_arg_len(bprm, len))
590 			goto out;
591 
592 		/* We're going to work our way backwards. */
593 		pos = bprm->p;
594 		str += len;
595 		bprm->p -= len;
596 		if (bprm_hit_stack_limit(bprm))
597 			goto out;
598 
599 		while (len > 0) {
600 			int offset, bytes_to_copy;
601 
602 			if (fatal_signal_pending(current)) {
603 				ret = -ERESTARTNOHAND;
604 				goto out;
605 			}
606 			cond_resched();
607 
608 			offset = pos % PAGE_SIZE;
609 			if (offset == 0)
610 				offset = PAGE_SIZE;
611 
612 			bytes_to_copy = offset;
613 			if (bytes_to_copy > len)
614 				bytes_to_copy = len;
615 
616 			offset -= bytes_to_copy;
617 			pos -= bytes_to_copy;
618 			str -= bytes_to_copy;
619 			len -= bytes_to_copy;
620 
621 			if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
622 				struct page *page;
623 
624 				page = get_arg_page(bprm, pos, 1);
625 				if (!page) {
626 					ret = -E2BIG;
627 					goto out;
628 				}
629 
630 				if (kmapped_page) {
631 					flush_dcache_page(kmapped_page);
632 					kunmap_local(kaddr);
633 					put_arg_page(kmapped_page);
634 				}
635 				kmapped_page = page;
636 				kaddr = kmap_local_page(kmapped_page);
637 				kpos = pos & PAGE_MASK;
638 				flush_arg_page(bprm, kpos, kmapped_page);
639 			}
640 			if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
641 				ret = -EFAULT;
642 				goto out;
643 			}
644 		}
645 	}
646 	ret = 0;
647 out:
648 	if (kmapped_page) {
649 		flush_dcache_page(kmapped_page);
650 		kunmap_local(kaddr);
651 		put_arg_page(kmapped_page);
652 	}
653 	return ret;
654 }
655 
656 /*
657  * Copy and argument/environment string from the kernel to the processes stack.
658  */
copy_string_kernel(const char * arg,struct linux_binprm * bprm)659 int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
660 {
661 	int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;
662 	unsigned long pos = bprm->p;
663 
664 	if (len == 0)
665 		return -EFAULT;
666 	if (!valid_arg_len(bprm, len))
667 		return -E2BIG;
668 
669 	/* We're going to work our way backwards. */
670 	arg += len;
671 	bprm->p -= len;
672 	if (bprm_hit_stack_limit(bprm))
673 		return -E2BIG;
674 
675 	while (len > 0) {
676 		unsigned int bytes_to_copy = min_t(unsigned int, len,
677 				min_not_zero(offset_in_page(pos), PAGE_SIZE));
678 		struct page *page;
679 
680 		pos -= bytes_to_copy;
681 		arg -= bytes_to_copy;
682 		len -= bytes_to_copy;
683 
684 		page = get_arg_page(bprm, pos, 1);
685 		if (!page)
686 			return -E2BIG;
687 		flush_arg_page(bprm, pos & PAGE_MASK, page);
688 		memcpy_to_page(page, offset_in_page(pos), arg, bytes_to_copy);
689 		put_arg_page(page);
690 	}
691 
692 	return 0;
693 }
694 EXPORT_SYMBOL(copy_string_kernel);
695 
copy_strings_kernel(int argc,const char * const * argv,struct linux_binprm * bprm)696 static int copy_strings_kernel(int argc, const char *const *argv,
697 			       struct linux_binprm *bprm)
698 {
699 	while (argc-- > 0) {
700 		int ret = copy_string_kernel(argv[argc], bprm);
701 		if (ret < 0)
702 			return ret;
703 		if (fatal_signal_pending(current))
704 			return -ERESTARTNOHAND;
705 		cond_resched();
706 	}
707 	return 0;
708 }
709 
710 #ifdef CONFIG_MMU
711 
712 /*
713  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
714  * the stack is optionally relocated, and some extra space is added.
715  */
setup_arg_pages(struct linux_binprm * bprm,unsigned long stack_top,int executable_stack)716 int setup_arg_pages(struct linux_binprm *bprm,
717 		    unsigned long stack_top,
718 		    int executable_stack)
719 {
720 	unsigned long ret;
721 	unsigned long stack_shift;
722 	struct mm_struct *mm = current->mm;
723 	struct vm_area_struct *vma = bprm->vma;
724 	struct vm_area_struct *prev = NULL;
725 	unsigned long vm_flags;
726 	unsigned long stack_base;
727 	unsigned long stack_size;
728 	unsigned long stack_expand;
729 	unsigned long rlim_stack;
730 	struct mmu_gather tlb;
731 	struct vma_iterator vmi;
732 
733 #ifdef CONFIG_STACK_GROWSUP
734 	/* Limit stack size */
735 	stack_base = bprm->rlim_stack.rlim_max;
736 
737 	stack_base = calc_max_stack_size(stack_base);
738 
739 	/* Add space for stack randomization. */
740 	if (current->flags & PF_RANDOMIZE)
741 		stack_base += (STACK_RND_MASK << PAGE_SHIFT);
742 
743 	/* Make sure we didn't let the argument array grow too large. */
744 	if (vma->vm_end - vma->vm_start > stack_base)
745 		return -ENOMEM;
746 
747 	stack_base = PAGE_ALIGN(stack_top - stack_base);
748 
749 	stack_shift = vma->vm_start - stack_base;
750 	mm->arg_start = bprm->p - stack_shift;
751 	bprm->p = vma->vm_end - stack_shift;
752 #else
753 	stack_top = arch_align_stack(stack_top);
754 	stack_top = PAGE_ALIGN(stack_top);
755 
756 	if (unlikely(stack_top < mmap_min_addr) ||
757 	    unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
758 		return -ENOMEM;
759 
760 	stack_shift = vma->vm_end - stack_top;
761 
762 	bprm->p -= stack_shift;
763 	mm->arg_start = bprm->p;
764 #endif
765 
766 	if (bprm->loader)
767 		bprm->loader -= stack_shift;
768 	bprm->exec -= stack_shift;
769 
770 	if (mmap_write_lock_killable(mm))
771 		return -EINTR;
772 
773 	vm_flags = VM_STACK_FLAGS;
774 
775 	/*
776 	 * Adjust stack execute permissions; explicitly enable for
777 	 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
778 	 * (arch default) otherwise.
779 	 */
780 	if (unlikely(executable_stack == EXSTACK_ENABLE_X))
781 		vm_flags |= VM_EXEC;
782 	else if (executable_stack == EXSTACK_DISABLE_X)
783 		vm_flags &= ~VM_EXEC;
784 	vm_flags |= mm->def_flags;
785 	vm_flags |= VM_STACK_INCOMPLETE_SETUP;
786 
787 	vma_iter_init(&vmi, mm, vma->vm_start);
788 
789 	tlb_gather_mmu(&tlb, mm);
790 	ret = mprotect_fixup(&vmi, &tlb, vma, &prev, vma->vm_start, vma->vm_end,
791 			vm_flags);
792 	tlb_finish_mmu(&tlb);
793 
794 	if (ret)
795 		goto out_unlock;
796 	BUG_ON(prev != vma);
797 
798 	if (unlikely(vm_flags & VM_EXEC)) {
799 		pr_warn_once("process '%pD4' started with executable stack\n",
800 			     bprm->file);
801 	}
802 
803 	/* Move stack pages down in memory. */
804 	if (stack_shift) {
805 		/*
806 		 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
807 		 * the binfmt code determines where the new stack should reside, we shift it to
808 		 * its final location.
809 		 */
810 		ret = relocate_vma_down(vma, stack_shift);
811 		if (ret)
812 			goto out_unlock;
813 	}
814 
815 	/* mprotect_fixup is overkill to remove the temporary stack flags */
816 	vm_flags_clear(vma, VM_STACK_INCOMPLETE_SETUP);
817 
818 	stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
819 	stack_size = vma->vm_end - vma->vm_start;
820 	/*
821 	 * Align this down to a page boundary as expand_stack
822 	 * will align it up.
823 	 */
824 	rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK;
825 
826 	stack_expand = min(rlim_stack, stack_size + stack_expand);
827 
828 #ifdef CONFIG_STACK_GROWSUP
829 	stack_base = vma->vm_start + stack_expand;
830 #else
831 	stack_base = vma->vm_end - stack_expand;
832 #endif
833 	current->mm->start_stack = bprm->p;
834 	ret = expand_stack_locked(vma, stack_base);
835 	if (ret)
836 		ret = -EFAULT;
837 
838 out_unlock:
839 	mmap_write_unlock(mm);
840 	return ret;
841 }
842 EXPORT_SYMBOL(setup_arg_pages);
843 
844 #else
845 
846 /*
847  * Transfer the program arguments and environment from the holding pages
848  * onto the stack. The provided stack pointer is adjusted accordingly.
849  */
transfer_args_to_stack(struct linux_binprm * bprm,unsigned long * sp_location)850 int transfer_args_to_stack(struct linux_binprm *bprm,
851 			   unsigned long *sp_location)
852 {
853 	unsigned long index, stop, sp;
854 	int ret = 0;
855 
856 	stop = bprm->p >> PAGE_SHIFT;
857 	sp = *sp_location;
858 
859 	for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
860 		unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
861 		char *src = kmap_local_page(bprm->page[index]) + offset;
862 		sp -= PAGE_SIZE - offset;
863 		if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
864 			ret = -EFAULT;
865 		kunmap_local(src);
866 		if (ret)
867 			goto out;
868 	}
869 
870 	bprm->exec += *sp_location - MAX_ARG_PAGES * PAGE_SIZE;
871 	*sp_location = sp;
872 
873 out:
874 	return ret;
875 }
876 EXPORT_SYMBOL(transfer_args_to_stack);
877 
878 #endif /* CONFIG_MMU */
879 
880 /*
881  * On success, caller must call do_close_execat() on the returned
882  * struct file to close it.
883  */
do_open_execat(int fd,struct filename * name,int flags)884 static struct file *do_open_execat(int fd, struct filename *name, int flags)
885 {
886 	struct file *file;
887 	struct open_flags open_exec_flags = {
888 		.open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
889 		.acc_mode = MAY_EXEC,
890 		.intent = LOOKUP_OPEN,
891 		.lookup_flags = LOOKUP_FOLLOW,
892 	};
893 
894 	if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
895 		return ERR_PTR(-EINVAL);
896 	if (flags & AT_SYMLINK_NOFOLLOW)
897 		open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
898 	if (flags & AT_EMPTY_PATH)
899 		open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
900 
901 	file = do_filp_open(fd, name, &open_exec_flags);
902 	if (IS_ERR(file))
903 		return file;
904 
905 	/*
906 	 * In the past the regular type check was here. It moved to may_open() in
907 	 * 633fb6ac3980 ("exec: move S_ISREG() check earlier"). Since then it is
908 	 * an invariant that all non-regular files error out before we get here.
909 	 */
910 	if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode)) ||
911 	    path_noexec(&file->f_path)) {
912 		fput(file);
913 		return ERR_PTR(-EACCES);
914 	}
915 
916 	return file;
917 }
918 
919 /**
920  * open_exec - Open a path name for execution
921  *
922  * @name: path name to open with the intent of executing it.
923  *
924  * Returns ERR_PTR on failure or allocated struct file on success.
925  *
926  * As this is a wrapper for the internal do_open_execat(). Also see
927  * do_close_execat().
928  */
open_exec(const char * name)929 struct file *open_exec(const char *name)
930 {
931 	struct filename *filename = getname_kernel(name);
932 	struct file *f = ERR_CAST(filename);
933 
934 	if (!IS_ERR(filename)) {
935 		f = do_open_execat(AT_FDCWD, filename, 0);
936 		putname(filename);
937 	}
938 	return f;
939 }
940 EXPORT_SYMBOL(open_exec);
941 
942 #if defined(CONFIG_BINFMT_FLAT) || defined(CONFIG_BINFMT_ELF_FDPIC)
read_code(struct file * file,unsigned long addr,loff_t pos,size_t len)943 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
944 {
945 	ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
946 	if (res > 0)
947 		flush_icache_user_range(addr, addr + len);
948 	return res;
949 }
950 EXPORT_SYMBOL(read_code);
951 #endif
952 
953 /*
954  * Maps the mm_struct mm into the current task struct.
955  * On success, this function returns with exec_update_lock
956  * held for writing.
957  */
exec_mmap(struct mm_struct * mm)958 static int exec_mmap(struct mm_struct *mm)
959 {
960 	struct task_struct *tsk;
961 	struct mm_struct *old_mm, *active_mm;
962 	int ret;
963 
964 	/* Notify parent that we're no longer interested in the old VM */
965 	tsk = current;
966 	old_mm = current->mm;
967 	exec_mm_release(tsk, old_mm);
968 
969 	ret = down_write_killable(&tsk->signal->exec_update_lock);
970 	if (ret)
971 		return ret;
972 
973 	if (old_mm) {
974 		/*
975 		 * If there is a pending fatal signal perhaps a signal
976 		 * whose default action is to create a coredump get
977 		 * out and die instead of going through with the exec.
978 		 */
979 		ret = mmap_read_lock_killable(old_mm);
980 		if (ret) {
981 			up_write(&tsk->signal->exec_update_lock);
982 			return ret;
983 		}
984 	}
985 
986 	task_lock(tsk);
987 	membarrier_exec_mmap(mm);
988 
989 	local_irq_disable();
990 	active_mm = tsk->active_mm;
991 	tsk->active_mm = mm;
992 	tsk->mm = mm;
993 	mm_init_cid(mm);
994 	/*
995 	 * This prevents preemption while active_mm is being loaded and
996 	 * it and mm are being updated, which could cause problems for
997 	 * lazy tlb mm refcounting when these are updated by context
998 	 * switches. Not all architectures can handle irqs off over
999 	 * activate_mm yet.
1000 	 */
1001 	if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
1002 		local_irq_enable();
1003 	activate_mm(active_mm, mm);
1004 	if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
1005 		local_irq_enable();
1006 	lru_gen_add_mm(mm);
1007 	task_unlock(tsk);
1008 	lru_gen_use_mm(mm);
1009 	if (old_mm) {
1010 		mmap_read_unlock(old_mm);
1011 		BUG_ON(active_mm != old_mm);
1012 		setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
1013 		mm_update_next_owner(old_mm);
1014 		mmput(old_mm);
1015 		return 0;
1016 	}
1017 	mmdrop_lazy_tlb(active_mm);
1018 	return 0;
1019 }
1020 
de_thread(struct task_struct * tsk)1021 static int de_thread(struct task_struct *tsk)
1022 {
1023 	struct signal_struct *sig = tsk->signal;
1024 	struct sighand_struct *oldsighand = tsk->sighand;
1025 	spinlock_t *lock = &oldsighand->siglock;
1026 
1027 	if (thread_group_empty(tsk))
1028 		goto no_thread_group;
1029 
1030 	/*
1031 	 * Kill all other threads in the thread group.
1032 	 */
1033 	spin_lock_irq(lock);
1034 	if ((sig->flags & SIGNAL_GROUP_EXIT) || sig->group_exec_task) {
1035 		/*
1036 		 * Another group action in progress, just
1037 		 * return so that the signal is processed.
1038 		 */
1039 		spin_unlock_irq(lock);
1040 		return -EAGAIN;
1041 	}
1042 
1043 	sig->group_exec_task = tsk;
1044 	sig->notify_count = zap_other_threads(tsk);
1045 	if (!thread_group_leader(tsk))
1046 		sig->notify_count--;
1047 
1048 	while (sig->notify_count) {
1049 		__set_current_state(TASK_KILLABLE);
1050 		spin_unlock_irq(lock);
1051 		schedule();
1052 		if (__fatal_signal_pending(tsk))
1053 			goto killed;
1054 		spin_lock_irq(lock);
1055 	}
1056 	spin_unlock_irq(lock);
1057 
1058 	/*
1059 	 * At this point all other threads have exited, all we have to
1060 	 * do is to wait for the thread group leader to become inactive,
1061 	 * and to assume its PID:
1062 	 */
1063 	if (!thread_group_leader(tsk)) {
1064 		struct task_struct *leader = tsk->group_leader;
1065 
1066 		for (;;) {
1067 			cgroup_threadgroup_change_begin(tsk);
1068 			write_lock_irq(&tasklist_lock);
1069 			/*
1070 			 * Do this under tasklist_lock to ensure that
1071 			 * exit_notify() can't miss ->group_exec_task
1072 			 */
1073 			sig->notify_count = -1;
1074 			if (likely(leader->exit_state))
1075 				break;
1076 			__set_current_state(TASK_KILLABLE);
1077 			write_unlock_irq(&tasklist_lock);
1078 			cgroup_threadgroup_change_end(tsk);
1079 			schedule();
1080 			if (__fatal_signal_pending(tsk))
1081 				goto killed;
1082 		}
1083 
1084 		/*
1085 		 * The only record we have of the real-time age of a
1086 		 * process, regardless of execs it's done, is start_time.
1087 		 * All the past CPU time is accumulated in signal_struct
1088 		 * from sister threads now dead.  But in this non-leader
1089 		 * exec, nothing survives from the original leader thread,
1090 		 * whose birth marks the true age of this process now.
1091 		 * When we take on its identity by switching to its PID, we
1092 		 * also take its birthdate (always earlier than our own).
1093 		 */
1094 		tsk->start_time = leader->start_time;
1095 		tsk->start_boottime = leader->start_boottime;
1096 
1097 		BUG_ON(!same_thread_group(leader, tsk));
1098 		/*
1099 		 * An exec() starts a new thread group with the
1100 		 * TGID of the previous thread group. Rehash the
1101 		 * two threads with a switched PID, and release
1102 		 * the former thread group leader:
1103 		 */
1104 
1105 		/* Become a process group leader with the old leader's pid.
1106 		 * The old leader becomes a thread of the this thread group.
1107 		 */
1108 		exchange_tids(tsk, leader);
1109 		transfer_pid(leader, tsk, PIDTYPE_TGID);
1110 		transfer_pid(leader, tsk, PIDTYPE_PGID);
1111 		transfer_pid(leader, tsk, PIDTYPE_SID);
1112 
1113 		list_replace_rcu(&leader->tasks, &tsk->tasks);
1114 		list_replace_init(&leader->sibling, &tsk->sibling);
1115 
1116 		tsk->group_leader = tsk;
1117 		leader->group_leader = tsk;
1118 
1119 		tsk->exit_signal = SIGCHLD;
1120 		leader->exit_signal = -1;
1121 
1122 		BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1123 		leader->exit_state = EXIT_DEAD;
1124 		/*
1125 		 * We are going to release_task()->ptrace_unlink() silently,
1126 		 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1127 		 * the tracer won't block again waiting for this thread.
1128 		 */
1129 		if (unlikely(leader->ptrace))
1130 			__wake_up_parent(leader, leader->parent);
1131 		write_unlock_irq(&tasklist_lock);
1132 		cgroup_threadgroup_change_end(tsk);
1133 
1134 		release_task(leader);
1135 	}
1136 
1137 	sig->group_exec_task = NULL;
1138 	sig->notify_count = 0;
1139 
1140 no_thread_group:
1141 	/* we have changed execution domain */
1142 	tsk->exit_signal = SIGCHLD;
1143 
1144 	BUG_ON(!thread_group_leader(tsk));
1145 	return 0;
1146 
1147 killed:
1148 	/* protects against exit_notify() and __exit_signal() */
1149 	read_lock(&tasklist_lock);
1150 	sig->group_exec_task = NULL;
1151 	sig->notify_count = 0;
1152 	read_unlock(&tasklist_lock);
1153 	return -EAGAIN;
1154 }
1155 
1156 
1157 /*
1158  * This function makes sure the current process has its own signal table,
1159  * so that flush_signal_handlers can later reset the handlers without
1160  * disturbing other processes.  (Other processes might share the signal
1161  * table via the CLONE_SIGHAND option to clone().)
1162  */
unshare_sighand(struct task_struct * me)1163 static int unshare_sighand(struct task_struct *me)
1164 {
1165 	struct sighand_struct *oldsighand = me->sighand;
1166 
1167 	if (refcount_read(&oldsighand->count) != 1) {
1168 		struct sighand_struct *newsighand;
1169 		/*
1170 		 * This ->sighand is shared with the CLONE_SIGHAND
1171 		 * but not CLONE_THREAD task, switch to the new one.
1172 		 */
1173 		newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1174 		if (!newsighand)
1175 			return -ENOMEM;
1176 
1177 		refcount_set(&newsighand->count, 1);
1178 
1179 		write_lock_irq(&tasklist_lock);
1180 		spin_lock(&oldsighand->siglock);
1181 		memcpy(newsighand->action, oldsighand->action,
1182 		       sizeof(newsighand->action));
1183 		rcu_assign_pointer(me->sighand, newsighand);
1184 		spin_unlock(&oldsighand->siglock);
1185 		write_unlock_irq(&tasklist_lock);
1186 
1187 		__cleanup_sighand(oldsighand);
1188 	}
1189 	return 0;
1190 }
1191 
__get_task_comm(char * buf,size_t buf_size,struct task_struct * tsk)1192 char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
1193 {
1194 	task_lock(tsk);
1195 	/* Always NUL terminated and zero-padded */
1196 	strscpy_pad(buf, tsk->comm, buf_size);
1197 	task_unlock(tsk);
1198 	return buf;
1199 }
1200 EXPORT_SYMBOL_GPL(__get_task_comm);
1201 
1202 /*
1203  * These functions flushes out all traces of the currently running executable
1204  * so that a new one can be started
1205  */
1206 
__set_task_comm(struct task_struct * tsk,const char * buf,bool exec)1207 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1208 {
1209 	task_lock(tsk);
1210 	trace_task_rename(tsk, buf);
1211 	strscpy_pad(tsk->comm, buf, sizeof(tsk->comm));
1212 	task_unlock(tsk);
1213 	perf_event_comm(tsk, exec);
1214 }
1215 
1216 /*
1217  * Calling this is the point of no return. None of the failures will be
1218  * seen by userspace since either the process is already taking a fatal
1219  * signal (via de_thread() or coredump), or will have SEGV raised
1220  * (after exec_mmap()) by search_binary_handler (see below).
1221  */
begin_new_exec(struct linux_binprm * bprm)1222 int begin_new_exec(struct linux_binprm * bprm)
1223 {
1224 	struct task_struct *me = current;
1225 	int retval;
1226 
1227 	/* Once we are committed compute the creds */
1228 	retval = bprm_creds_from_file(bprm);
1229 	if (retval)
1230 		return retval;
1231 
1232 	/*
1233 	 * This tracepoint marks the point before flushing the old exec where
1234 	 * the current task is still unchanged, but errors are fatal (point of
1235 	 * no return). The later "sched_process_exec" tracepoint is called after
1236 	 * the current task has successfully switched to the new exec.
1237 	 */
1238 	trace_sched_prepare_exec(current, bprm);
1239 
1240 	/*
1241 	 * Ensure all future errors are fatal.
1242 	 */
1243 	bprm->point_of_no_return = true;
1244 
1245 	/*
1246 	 * Make this the only thread in the thread group.
1247 	 */
1248 	retval = de_thread(me);
1249 	if (retval)
1250 		goto out;
1251 
1252 	/*
1253 	 * Cancel any io_uring activity across execve
1254 	 */
1255 	io_uring_task_cancel();
1256 
1257 	/* Ensure the files table is not shared. */
1258 	retval = unshare_files();
1259 	if (retval)
1260 		goto out;
1261 
1262 	/*
1263 	 * Must be called _before_ exec_mmap() as bprm->mm is
1264 	 * not visible until then. Doing it here also ensures
1265 	 * we don't race against replace_mm_exe_file().
1266 	 */
1267 	retval = set_mm_exe_file(bprm->mm, bprm->file);
1268 	if (retval)
1269 		goto out;
1270 
1271 	/* If the binary is not readable then enforce mm->dumpable=0 */
1272 	would_dump(bprm, bprm->file);
1273 	if (bprm->have_execfd)
1274 		would_dump(bprm, bprm->executable);
1275 
1276 	/*
1277 	 * Release all of the old mmap stuff
1278 	 */
1279 	acct_arg_size(bprm, 0);
1280 	retval = exec_mmap(bprm->mm);
1281 	if (retval)
1282 		goto out;
1283 
1284 	bprm->mm = NULL;
1285 
1286 	retval = exec_task_namespaces();
1287 	if (retval)
1288 		goto out_unlock;
1289 
1290 #ifdef CONFIG_POSIX_TIMERS
1291 	spin_lock_irq(&me->sighand->siglock);
1292 	posix_cpu_timers_exit(me);
1293 	spin_unlock_irq(&me->sighand->siglock);
1294 	exit_itimers(me);
1295 	flush_itimer_signals();
1296 #endif
1297 
1298 	/*
1299 	 * Make the signal table private.
1300 	 */
1301 	retval = unshare_sighand(me);
1302 	if (retval)
1303 		goto out_unlock;
1304 
1305 	me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC |
1306 					PF_NOFREEZE | PF_NO_SETAFFINITY);
1307 	flush_thread();
1308 	me->personality &= ~bprm->per_clear;
1309 
1310 	clear_syscall_work_syscall_user_dispatch(me);
1311 
1312 	/*
1313 	 * We have to apply CLOEXEC before we change whether the process is
1314 	 * dumpable (in setup_new_exec) to avoid a race with a process in userspace
1315 	 * trying to access the should-be-closed file descriptors of a process
1316 	 * undergoing exec(2).
1317 	 */
1318 	do_close_on_exec(me->files);
1319 
1320 	if (bprm->secureexec) {
1321 		/* Make sure parent cannot signal privileged process. */
1322 		me->pdeath_signal = 0;
1323 
1324 		/*
1325 		 * For secureexec, reset the stack limit to sane default to
1326 		 * avoid bad behavior from the prior rlimits. This has to
1327 		 * happen before arch_pick_mmap_layout(), which examines
1328 		 * RLIMIT_STACK, but after the point of no return to avoid
1329 		 * needing to clean up the change on failure.
1330 		 */
1331 		if (bprm->rlim_stack.rlim_cur > _STK_LIM)
1332 			bprm->rlim_stack.rlim_cur = _STK_LIM;
1333 	}
1334 
1335 	me->sas_ss_sp = me->sas_ss_size = 0;
1336 
1337 	/*
1338 	 * Figure out dumpability. Note that this checking only of current
1339 	 * is wrong, but userspace depends on it. This should be testing
1340 	 * bprm->secureexec instead.
1341 	 */
1342 	if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
1343 	    !(uid_eq(current_euid(), current_uid()) &&
1344 	      gid_eq(current_egid(), current_gid())))
1345 		set_dumpable(current->mm, suid_dumpable);
1346 	else
1347 		set_dumpable(current->mm, SUID_DUMP_USER);
1348 
1349 	perf_event_exec();
1350 	__set_task_comm(me, kbasename(bprm->filename), true);
1351 
1352 	/* An exec changes our domain. We are no longer part of the thread
1353 	   group */
1354 	WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1);
1355 	flush_signal_handlers(me, 0);
1356 
1357 	retval = set_cred_ucounts(bprm->cred);
1358 	if (retval < 0)
1359 		goto out_unlock;
1360 
1361 	/*
1362 	 * install the new credentials for this executable
1363 	 */
1364 	security_bprm_committing_creds(bprm);
1365 
1366 	commit_creds(bprm->cred);
1367 	bprm->cred = NULL;
1368 
1369 	/*
1370 	 * Disable monitoring for regular users
1371 	 * when executing setuid binaries. Must
1372 	 * wait until new credentials are committed
1373 	 * by commit_creds() above
1374 	 */
1375 	if (get_dumpable(me->mm) != SUID_DUMP_USER)
1376 		perf_event_exit_task(me);
1377 	/*
1378 	 * cred_guard_mutex must be held at least to this point to prevent
1379 	 * ptrace_attach() from altering our determination of the task's
1380 	 * credentials; any time after this it may be unlocked.
1381 	 */
1382 	security_bprm_committed_creds(bprm);
1383 
1384 	/* Pass the opened binary to the interpreter. */
1385 	if (bprm->have_execfd) {
1386 		retval = get_unused_fd_flags(0);
1387 		if (retval < 0)
1388 			goto out_unlock;
1389 		fd_install(retval, bprm->executable);
1390 		bprm->executable = NULL;
1391 		bprm->execfd = retval;
1392 	}
1393 	return 0;
1394 
1395 out_unlock:
1396 	up_write(&me->signal->exec_update_lock);
1397 	if (!bprm->cred)
1398 		mutex_unlock(&me->signal->cred_guard_mutex);
1399 
1400 out:
1401 	return retval;
1402 }
1403 EXPORT_SYMBOL(begin_new_exec);
1404 
would_dump(struct linux_binprm * bprm,struct file * file)1405 void would_dump(struct linux_binprm *bprm, struct file *file)
1406 {
1407 	struct inode *inode = file_inode(file);
1408 	struct mnt_idmap *idmap = file_mnt_idmap(file);
1409 	if (inode_permission(idmap, inode, MAY_READ) < 0) {
1410 		struct user_namespace *old, *user_ns;
1411 		bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1412 
1413 		/* Ensure mm->user_ns contains the executable */
1414 		user_ns = old = bprm->mm->user_ns;
1415 		while ((user_ns != &init_user_ns) &&
1416 		       !privileged_wrt_inode_uidgid(user_ns, idmap, inode))
1417 			user_ns = user_ns->parent;
1418 
1419 		if (old != user_ns) {
1420 			bprm->mm->user_ns = get_user_ns(user_ns);
1421 			put_user_ns(old);
1422 		}
1423 	}
1424 }
1425 EXPORT_SYMBOL(would_dump);
1426 
setup_new_exec(struct linux_binprm * bprm)1427 void setup_new_exec(struct linux_binprm * bprm)
1428 {
1429 	/* Setup things that can depend upon the personality */
1430 	struct task_struct *me = current;
1431 
1432 	arch_pick_mmap_layout(me->mm, &bprm->rlim_stack);
1433 
1434 	arch_setup_new_exec();
1435 
1436 	/* Set the new mm task size. We have to do that late because it may
1437 	 * depend on TIF_32BIT which is only updated in flush_thread() on
1438 	 * some architectures like powerpc
1439 	 */
1440 	me->mm->task_size = TASK_SIZE;
1441 	up_write(&me->signal->exec_update_lock);
1442 	mutex_unlock(&me->signal->cred_guard_mutex);
1443 }
1444 EXPORT_SYMBOL(setup_new_exec);
1445 
1446 /* Runs immediately before start_thread() takes over. */
finalize_exec(struct linux_binprm * bprm)1447 void finalize_exec(struct linux_binprm *bprm)
1448 {
1449 	/* Store any stack rlimit changes before starting thread. */
1450 	task_lock(current->group_leader);
1451 	current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack;
1452 	task_unlock(current->group_leader);
1453 }
1454 EXPORT_SYMBOL(finalize_exec);
1455 
1456 /*
1457  * Prepare credentials and lock ->cred_guard_mutex.
1458  * setup_new_exec() commits the new creds and drops the lock.
1459  * Or, if exec fails before, free_bprm() should release ->cred
1460  * and unlock.
1461  */
prepare_bprm_creds(struct linux_binprm * bprm)1462 static int prepare_bprm_creds(struct linux_binprm *bprm)
1463 {
1464 	if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1465 		return -ERESTARTNOINTR;
1466 
1467 	bprm->cred = prepare_exec_creds();
1468 	if (likely(bprm->cred))
1469 		return 0;
1470 
1471 	mutex_unlock(&current->signal->cred_guard_mutex);
1472 	return -ENOMEM;
1473 }
1474 
1475 /* Matches do_open_execat() */
do_close_execat(struct file * file)1476 static void do_close_execat(struct file *file)
1477 {
1478 	if (file)
1479 		fput(file);
1480 }
1481 
free_bprm(struct linux_binprm * bprm)1482 static void free_bprm(struct linux_binprm *bprm)
1483 {
1484 	if (bprm->mm) {
1485 		acct_arg_size(bprm, 0);
1486 		mmput(bprm->mm);
1487 	}
1488 	free_arg_pages(bprm);
1489 	if (bprm->cred) {
1490 		mutex_unlock(&current->signal->cred_guard_mutex);
1491 		abort_creds(bprm->cred);
1492 	}
1493 	do_close_execat(bprm->file);
1494 	if (bprm->executable)
1495 		fput(bprm->executable);
1496 	/* If a binfmt changed the interp, free it. */
1497 	if (bprm->interp != bprm->filename)
1498 		kfree(bprm->interp);
1499 	kfree(bprm->fdpath);
1500 	kfree(bprm);
1501 }
1502 
alloc_bprm(int fd,struct filename * filename,int flags)1503 static struct linux_binprm *alloc_bprm(int fd, struct filename *filename, int flags)
1504 {
1505 	struct linux_binprm *bprm;
1506 	struct file *file;
1507 	int retval = -ENOMEM;
1508 
1509 	file = do_open_execat(fd, filename, flags);
1510 	if (IS_ERR(file))
1511 		return ERR_CAST(file);
1512 
1513 	bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1514 	if (!bprm) {
1515 		do_close_execat(file);
1516 		return ERR_PTR(-ENOMEM);
1517 	}
1518 
1519 	bprm->file = file;
1520 
1521 	if (fd == AT_FDCWD || filename->name[0] == '/') {
1522 		bprm->filename = filename->name;
1523 	} else {
1524 		if (filename->name[0] == '\0')
1525 			bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd);
1526 		else
1527 			bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s",
1528 						  fd, filename->name);
1529 		if (!bprm->fdpath)
1530 			goto out_free;
1531 
1532 		/*
1533 		 * Record that a name derived from an O_CLOEXEC fd will be
1534 		 * inaccessible after exec.  This allows the code in exec to
1535 		 * choose to fail when the executable is not mmaped into the
1536 		 * interpreter and an open file descriptor is not passed to
1537 		 * the interpreter.  This makes for a better user experience
1538 		 * than having the interpreter start and then immediately fail
1539 		 * when it finds the executable is inaccessible.
1540 		 */
1541 		if (get_close_on_exec(fd))
1542 			bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1543 
1544 		bprm->filename = bprm->fdpath;
1545 	}
1546 	bprm->interp = bprm->filename;
1547 
1548 	retval = bprm_mm_init(bprm);
1549 	if (!retval)
1550 		return bprm;
1551 
1552 out_free:
1553 	free_bprm(bprm);
1554 	return ERR_PTR(retval);
1555 }
1556 
bprm_change_interp(const char * interp,struct linux_binprm * bprm)1557 int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
1558 {
1559 	/* If a binfmt changed the interp, free it first. */
1560 	if (bprm->interp != bprm->filename)
1561 		kfree(bprm->interp);
1562 	bprm->interp = kstrdup(interp, GFP_KERNEL);
1563 	if (!bprm->interp)
1564 		return -ENOMEM;
1565 	return 0;
1566 }
1567 EXPORT_SYMBOL(bprm_change_interp);
1568 
1569 /*
1570  * determine how safe it is to execute the proposed program
1571  * - the caller must hold ->cred_guard_mutex to protect against
1572  *   PTRACE_ATTACH or seccomp thread-sync
1573  */
check_unsafe_exec(struct linux_binprm * bprm)1574 static void check_unsafe_exec(struct linux_binprm *bprm)
1575 {
1576 	struct task_struct *p = current, *t;
1577 	unsigned n_fs;
1578 
1579 	if (p->ptrace)
1580 		bprm->unsafe |= LSM_UNSAFE_PTRACE;
1581 
1582 	/*
1583 	 * This isn't strictly necessary, but it makes it harder for LSMs to
1584 	 * mess up.
1585 	 */
1586 	if (task_no_new_privs(current))
1587 		bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1588 
1589 	/*
1590 	 * If another task is sharing our fs, we cannot safely
1591 	 * suid exec because the differently privileged task
1592 	 * will be able to manipulate the current directory, etc.
1593 	 * It would be nice to force an unshare instead...
1594 	 */
1595 	n_fs = 1;
1596 	spin_lock(&p->fs->lock);
1597 	rcu_read_lock();
1598 	for_other_threads(p, t) {
1599 		if (t->fs == p->fs)
1600 			n_fs++;
1601 	}
1602 	rcu_read_unlock();
1603 
1604 	/* "users" and "in_exec" locked for copy_fs() */
1605 	if (p->fs->users > n_fs)
1606 		bprm->unsafe |= LSM_UNSAFE_SHARE;
1607 	else
1608 		p->fs->in_exec = 1;
1609 	spin_unlock(&p->fs->lock);
1610 }
1611 
bprm_fill_uid(struct linux_binprm * bprm,struct file * file)1612 static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
1613 {
1614 	/* Handle suid and sgid on files */
1615 	struct mnt_idmap *idmap;
1616 	struct inode *inode = file_inode(file);
1617 	unsigned int mode;
1618 	vfsuid_t vfsuid;
1619 	vfsgid_t vfsgid;
1620 	int err;
1621 
1622 	if (!mnt_may_suid(file->f_path.mnt))
1623 		return;
1624 
1625 	if (task_no_new_privs(current))
1626 		return;
1627 
1628 	mode = READ_ONCE(inode->i_mode);
1629 	if (!(mode & (S_ISUID|S_ISGID)))
1630 		return;
1631 
1632 	idmap = file_mnt_idmap(file);
1633 
1634 	/* Be careful if suid/sgid is set */
1635 	inode_lock(inode);
1636 
1637 	/* Atomically reload and check mode/uid/gid now that lock held. */
1638 	mode = inode->i_mode;
1639 	vfsuid = i_uid_into_vfsuid(idmap, inode);
1640 	vfsgid = i_gid_into_vfsgid(idmap, inode);
1641 	err = inode_permission(idmap, inode, MAY_EXEC);
1642 	inode_unlock(inode);
1643 
1644 	/* Did the exec bit vanish out from under us? Give up. */
1645 	if (err)
1646 		return;
1647 
1648 	/* We ignore suid/sgid if there are no mappings for them in the ns */
1649 	if (!vfsuid_has_mapping(bprm->cred->user_ns, vfsuid) ||
1650 	    !vfsgid_has_mapping(bprm->cred->user_ns, vfsgid))
1651 		return;
1652 
1653 	if (mode & S_ISUID) {
1654 		bprm->per_clear |= PER_CLEAR_ON_SETID;
1655 		bprm->cred->euid = vfsuid_into_kuid(vfsuid);
1656 	}
1657 
1658 	if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1659 		bprm->per_clear |= PER_CLEAR_ON_SETID;
1660 		bprm->cred->egid = vfsgid_into_kgid(vfsgid);
1661 	}
1662 }
1663 
1664 /*
1665  * Compute brpm->cred based upon the final binary.
1666  */
bprm_creds_from_file(struct linux_binprm * bprm)1667 static int bprm_creds_from_file(struct linux_binprm *bprm)
1668 {
1669 	/* Compute creds based on which file? */
1670 	struct file *file = bprm->execfd_creds ? bprm->executable : bprm->file;
1671 
1672 	bprm_fill_uid(bprm, file);
1673 	return security_bprm_creds_from_file(bprm, file);
1674 }
1675 
1676 /*
1677  * Fill the binprm structure from the inode.
1678  * Read the first BINPRM_BUF_SIZE bytes
1679  *
1680  * This may be called multiple times for binary chains (scripts for example).
1681  */
prepare_binprm(struct linux_binprm * bprm)1682 static int prepare_binprm(struct linux_binprm *bprm)
1683 {
1684 	loff_t pos = 0;
1685 
1686 	memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1687 	return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
1688 }
1689 
1690 /*
1691  * Arguments are '\0' separated strings found at the location bprm->p
1692  * points to; chop off the first by relocating brpm->p to right after
1693  * the first '\0' encountered.
1694  */
remove_arg_zero(struct linux_binprm * bprm)1695 int remove_arg_zero(struct linux_binprm *bprm)
1696 {
1697 	unsigned long offset;
1698 	char *kaddr;
1699 	struct page *page;
1700 
1701 	if (!bprm->argc)
1702 		return 0;
1703 
1704 	do {
1705 		offset = bprm->p & ~PAGE_MASK;
1706 		page = get_arg_page(bprm, bprm->p, 0);
1707 		if (!page)
1708 			return -EFAULT;
1709 		kaddr = kmap_local_page(page);
1710 
1711 		for (; offset < PAGE_SIZE && kaddr[offset];
1712 				offset++, bprm->p++)
1713 			;
1714 
1715 		kunmap_local(kaddr);
1716 		put_arg_page(page);
1717 	} while (offset == PAGE_SIZE);
1718 
1719 	bprm->p++;
1720 	bprm->argc--;
1721 
1722 	return 0;
1723 }
1724 EXPORT_SYMBOL(remove_arg_zero);
1725 
1726 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1727 /*
1728  * cycle the list of binary formats handler, until one recognizes the image
1729  */
search_binary_handler(struct linux_binprm * bprm)1730 static int search_binary_handler(struct linux_binprm *bprm)
1731 {
1732 	bool need_retry = IS_ENABLED(CONFIG_MODULES);
1733 	struct linux_binfmt *fmt;
1734 	int retval;
1735 
1736 	retval = prepare_binprm(bprm);
1737 	if (retval < 0)
1738 		return retval;
1739 
1740 	retval = security_bprm_check(bprm);
1741 	if (retval)
1742 		return retval;
1743 
1744 	retval = -ENOENT;
1745  retry:
1746 	read_lock(&binfmt_lock);
1747 	list_for_each_entry(fmt, &formats, lh) {
1748 		if (!try_module_get(fmt->module))
1749 			continue;
1750 		read_unlock(&binfmt_lock);
1751 
1752 		retval = fmt->load_binary(bprm);
1753 
1754 		read_lock(&binfmt_lock);
1755 		put_binfmt(fmt);
1756 		if (bprm->point_of_no_return || (retval != -ENOEXEC)) {
1757 			read_unlock(&binfmt_lock);
1758 			return retval;
1759 		}
1760 	}
1761 	read_unlock(&binfmt_lock);
1762 
1763 	if (need_retry) {
1764 		if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1765 		    printable(bprm->buf[2]) && printable(bprm->buf[3]))
1766 			return retval;
1767 		if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1768 			return retval;
1769 		need_retry = false;
1770 		goto retry;
1771 	}
1772 
1773 	return retval;
1774 }
1775 
1776 /* binfmt handlers will call back into begin_new_exec() on success. */
exec_binprm(struct linux_binprm * bprm)1777 static int exec_binprm(struct linux_binprm *bprm)
1778 {
1779 	pid_t old_pid, old_vpid;
1780 	int ret, depth;
1781 
1782 	/* Need to fetch pid before load_binary changes it */
1783 	old_pid = current->pid;
1784 	rcu_read_lock();
1785 	old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1786 	rcu_read_unlock();
1787 
1788 	/* This allows 4 levels of binfmt rewrites before failing hard. */
1789 	for (depth = 0;; depth++) {
1790 		struct file *exec;
1791 		if (depth > 5)
1792 			return -ELOOP;
1793 
1794 		ret = search_binary_handler(bprm);
1795 		if (ret < 0)
1796 			return ret;
1797 		if (!bprm->interpreter)
1798 			break;
1799 
1800 		exec = bprm->file;
1801 		bprm->file = bprm->interpreter;
1802 		bprm->interpreter = NULL;
1803 
1804 		if (unlikely(bprm->have_execfd)) {
1805 			if (bprm->executable) {
1806 				fput(exec);
1807 				return -ENOEXEC;
1808 			}
1809 			bprm->executable = exec;
1810 		} else
1811 			fput(exec);
1812 	}
1813 
1814 	audit_bprm(bprm);
1815 	trace_sched_process_exec(current, old_pid, bprm);
1816 	ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1817 	proc_exec_connector(current);
1818 	return 0;
1819 }
1820 
bprm_execve(struct linux_binprm * bprm)1821 static int bprm_execve(struct linux_binprm *bprm)
1822 {
1823 	int retval;
1824 
1825 	retval = prepare_bprm_creds(bprm);
1826 	if (retval)
1827 		return retval;
1828 
1829 	/*
1830 	 * Check for unsafe execution states before exec_binprm(), which
1831 	 * will call back into begin_new_exec(), into bprm_creds_from_file(),
1832 	 * where setuid-ness is evaluated.
1833 	 */
1834 	check_unsafe_exec(bprm);
1835 	current->in_execve = 1;
1836 	sched_mm_cid_before_execve(current);
1837 
1838 	sched_exec();
1839 
1840 	/* Set the unchanging part of bprm->cred */
1841 	retval = security_bprm_creds_for_exec(bprm);
1842 	if (retval)
1843 		goto out;
1844 
1845 	retval = exec_binprm(bprm);
1846 	if (retval < 0)
1847 		goto out;
1848 
1849 	sched_mm_cid_after_execve(current);
1850 	/* execve succeeded */
1851 	current->fs->in_exec = 0;
1852 	current->in_execve = 0;
1853 	rseq_execve(current);
1854 	user_events_execve(current);
1855 	acct_update_integrals(current);
1856 	task_numa_free(current, false);
1857 	return retval;
1858 
1859 out:
1860 	/*
1861 	 * If past the point of no return ensure the code never
1862 	 * returns to the userspace process.  Use an existing fatal
1863 	 * signal if present otherwise terminate the process with
1864 	 * SIGSEGV.
1865 	 */
1866 	if (bprm->point_of_no_return && !fatal_signal_pending(current))
1867 		force_fatal_sig(SIGSEGV);
1868 
1869 	sched_mm_cid_after_execve(current);
1870 	current->fs->in_exec = 0;
1871 	current->in_execve = 0;
1872 
1873 	return retval;
1874 }
1875 
do_execveat_common(int fd,struct filename * filename,struct user_arg_ptr argv,struct user_arg_ptr envp,int flags)1876 static int do_execveat_common(int fd, struct filename *filename,
1877 			      struct user_arg_ptr argv,
1878 			      struct user_arg_ptr envp,
1879 			      int flags)
1880 {
1881 	struct linux_binprm *bprm;
1882 	int retval;
1883 
1884 	if (IS_ERR(filename))
1885 		return PTR_ERR(filename);
1886 
1887 	/*
1888 	 * We move the actual failure in case of RLIMIT_NPROC excess from
1889 	 * set*uid() to execve() because too many poorly written programs
1890 	 * don't check setuid() return code.  Here we additionally recheck
1891 	 * whether NPROC limit is still exceeded.
1892 	 */
1893 	if ((current->flags & PF_NPROC_EXCEEDED) &&
1894 	    is_rlimit_overlimit(current_ucounts(), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
1895 		retval = -EAGAIN;
1896 		goto out_ret;
1897 	}
1898 
1899 	/* We're below the limit (still or again), so we don't want to make
1900 	 * further execve() calls fail. */
1901 	current->flags &= ~PF_NPROC_EXCEEDED;
1902 
1903 	bprm = alloc_bprm(fd, filename, flags);
1904 	if (IS_ERR(bprm)) {
1905 		retval = PTR_ERR(bprm);
1906 		goto out_ret;
1907 	}
1908 
1909 	retval = count(argv, MAX_ARG_STRINGS);
1910 	if (retval == 0)
1911 		pr_warn_once("process '%s' launched '%s' with NULL argv: empty string added\n",
1912 			     current->comm, bprm->filename);
1913 	if (retval < 0)
1914 		goto out_free;
1915 	bprm->argc = retval;
1916 
1917 	retval = count(envp, MAX_ARG_STRINGS);
1918 	if (retval < 0)
1919 		goto out_free;
1920 	bprm->envc = retval;
1921 
1922 	retval = bprm_stack_limits(bprm);
1923 	if (retval < 0)
1924 		goto out_free;
1925 
1926 	retval = copy_string_kernel(bprm->filename, bprm);
1927 	if (retval < 0)
1928 		goto out_free;
1929 	bprm->exec = bprm->p;
1930 
1931 	retval = copy_strings(bprm->envc, envp, bprm);
1932 	if (retval < 0)
1933 		goto out_free;
1934 
1935 	retval = copy_strings(bprm->argc, argv, bprm);
1936 	if (retval < 0)
1937 		goto out_free;
1938 
1939 	/*
1940 	 * When argv is empty, add an empty string ("") as argv[0] to
1941 	 * ensure confused userspace programs that start processing
1942 	 * from argv[1] won't end up walking envp. See also
1943 	 * bprm_stack_limits().
1944 	 */
1945 	if (bprm->argc == 0) {
1946 		retval = copy_string_kernel("", bprm);
1947 		if (retval < 0)
1948 			goto out_free;
1949 		bprm->argc = 1;
1950 	}
1951 
1952 	retval = bprm_execve(bprm);
1953 out_free:
1954 	free_bprm(bprm);
1955 
1956 out_ret:
1957 	putname(filename);
1958 	return retval;
1959 }
1960 
kernel_execve(const char * kernel_filename,const char * const * argv,const char * const * envp)1961 int kernel_execve(const char *kernel_filename,
1962 		  const char *const *argv, const char *const *envp)
1963 {
1964 	struct filename *filename;
1965 	struct linux_binprm *bprm;
1966 	int fd = AT_FDCWD;
1967 	int retval;
1968 
1969 	/* It is non-sense for kernel threads to call execve */
1970 	if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
1971 		return -EINVAL;
1972 
1973 	filename = getname_kernel(kernel_filename);
1974 	if (IS_ERR(filename))
1975 		return PTR_ERR(filename);
1976 
1977 	bprm = alloc_bprm(fd, filename, 0);
1978 	if (IS_ERR(bprm)) {
1979 		retval = PTR_ERR(bprm);
1980 		goto out_ret;
1981 	}
1982 
1983 	retval = count_strings_kernel(argv);
1984 	if (WARN_ON_ONCE(retval == 0))
1985 		retval = -EINVAL;
1986 	if (retval < 0)
1987 		goto out_free;
1988 	bprm->argc = retval;
1989 
1990 	retval = count_strings_kernel(envp);
1991 	if (retval < 0)
1992 		goto out_free;
1993 	bprm->envc = retval;
1994 
1995 	retval = bprm_stack_limits(bprm);
1996 	if (retval < 0)
1997 		goto out_free;
1998 
1999 	retval = copy_string_kernel(bprm->filename, bprm);
2000 	if (retval < 0)
2001 		goto out_free;
2002 	bprm->exec = bprm->p;
2003 
2004 	retval = copy_strings_kernel(bprm->envc, envp, bprm);
2005 	if (retval < 0)
2006 		goto out_free;
2007 
2008 	retval = copy_strings_kernel(bprm->argc, argv, bprm);
2009 	if (retval < 0)
2010 		goto out_free;
2011 
2012 	retval = bprm_execve(bprm);
2013 out_free:
2014 	free_bprm(bprm);
2015 out_ret:
2016 	putname(filename);
2017 	return retval;
2018 }
2019 
do_execve(struct filename * filename,const char __user * const __user * __argv,const char __user * const __user * __envp)2020 static int do_execve(struct filename *filename,
2021 	const char __user *const __user *__argv,
2022 	const char __user *const __user *__envp)
2023 {
2024 	struct user_arg_ptr argv = { .ptr.native = __argv };
2025 	struct user_arg_ptr envp = { .ptr.native = __envp };
2026 	return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
2027 }
2028 
do_execveat(int fd,struct filename * filename,const char __user * const __user * __argv,const char __user * const __user * __envp,int flags)2029 static int do_execveat(int fd, struct filename *filename,
2030 		const char __user *const __user *__argv,
2031 		const char __user *const __user *__envp,
2032 		int flags)
2033 {
2034 	struct user_arg_ptr argv = { .ptr.native = __argv };
2035 	struct user_arg_ptr envp = { .ptr.native = __envp };
2036 
2037 	return do_execveat_common(fd, filename, argv, envp, flags);
2038 }
2039 
2040 #ifdef CONFIG_COMPAT
compat_do_execve(struct filename * filename,const compat_uptr_t __user * __argv,const compat_uptr_t __user * __envp)2041 static int compat_do_execve(struct filename *filename,
2042 	const compat_uptr_t __user *__argv,
2043 	const compat_uptr_t __user *__envp)
2044 {
2045 	struct user_arg_ptr argv = {
2046 		.is_compat = true,
2047 		.ptr.compat = __argv,
2048 	};
2049 	struct user_arg_ptr envp = {
2050 		.is_compat = true,
2051 		.ptr.compat = __envp,
2052 	};
2053 	return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
2054 }
2055 
compat_do_execveat(int fd,struct filename * filename,const compat_uptr_t __user * __argv,const compat_uptr_t __user * __envp,int flags)2056 static int compat_do_execveat(int fd, struct filename *filename,
2057 			      const compat_uptr_t __user *__argv,
2058 			      const compat_uptr_t __user *__envp,
2059 			      int flags)
2060 {
2061 	struct user_arg_ptr argv = {
2062 		.is_compat = true,
2063 		.ptr.compat = __argv,
2064 	};
2065 	struct user_arg_ptr envp = {
2066 		.is_compat = true,
2067 		.ptr.compat = __envp,
2068 	};
2069 	return do_execveat_common(fd, filename, argv, envp, flags);
2070 }
2071 #endif
2072 
set_binfmt(struct linux_binfmt * new)2073 void set_binfmt(struct linux_binfmt *new)
2074 {
2075 	struct mm_struct *mm = current->mm;
2076 
2077 	if (mm->binfmt)
2078 		module_put(mm->binfmt->module);
2079 
2080 	mm->binfmt = new;
2081 	if (new)
2082 		__module_get(new->module);
2083 }
2084 EXPORT_SYMBOL(set_binfmt);
2085 
2086 /*
2087  * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
2088  */
set_dumpable(struct mm_struct * mm,int value)2089 void set_dumpable(struct mm_struct *mm, int value)
2090 {
2091 	if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
2092 		return;
2093 
2094 	set_mask_bits(&mm->flags, MMF_DUMPABLE_MASK, value);
2095 }
2096 
SYSCALL_DEFINE3(execve,const char __user *,filename,const char __user * const __user *,argv,const char __user * const __user *,envp)2097 SYSCALL_DEFINE3(execve,
2098 		const char __user *, filename,
2099 		const char __user *const __user *, argv,
2100 		const char __user *const __user *, envp)
2101 {
2102 	return do_execve(getname(filename), argv, envp);
2103 }
2104 
SYSCALL_DEFINE5(execveat,int,fd,const char __user *,filename,const char __user * const __user *,argv,const char __user * const __user *,envp,int,flags)2105 SYSCALL_DEFINE5(execveat,
2106 		int, fd, const char __user *, filename,
2107 		const char __user *const __user *, argv,
2108 		const char __user *const __user *, envp,
2109 		int, flags)
2110 {
2111 	return do_execveat(fd,
2112 			   getname_uflags(filename, flags),
2113 			   argv, envp, flags);
2114 }
2115 
2116 #ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE3(execve,const char __user *,filename,const compat_uptr_t __user *,argv,const compat_uptr_t __user *,envp)2117 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
2118 	const compat_uptr_t __user *, argv,
2119 	const compat_uptr_t __user *, envp)
2120 {
2121 	return compat_do_execve(getname(filename), argv, envp);
2122 }
2123 
COMPAT_SYSCALL_DEFINE5(execveat,int,fd,const char __user *,filename,const compat_uptr_t __user *,argv,const compat_uptr_t __user *,envp,int,flags)2124 COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
2125 		       const char __user *, filename,
2126 		       const compat_uptr_t __user *, argv,
2127 		       const compat_uptr_t __user *, envp,
2128 		       int,  flags)
2129 {
2130 	return compat_do_execveat(fd,
2131 				  getname_uflags(filename, flags),
2132 				  argv, envp, flags);
2133 }
2134 #endif
2135 
2136 #ifdef CONFIG_SYSCTL
2137 
proc_dointvec_minmax_coredump(const struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)2138 static int proc_dointvec_minmax_coredump(const struct ctl_table *table, int write,
2139 		void *buffer, size_t *lenp, loff_t *ppos)
2140 {
2141 	int error = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
2142 
2143 	if (!error)
2144 		validate_coredump_safety();
2145 	return error;
2146 }
2147 
2148 static struct ctl_table fs_exec_sysctls[] = {
2149 	{
2150 		.procname	= "suid_dumpable",
2151 		.data		= &suid_dumpable,
2152 		.maxlen		= sizeof(int),
2153 		.mode		= 0644,
2154 		.proc_handler	= proc_dointvec_minmax_coredump,
2155 		.extra1		= SYSCTL_ZERO,
2156 		.extra2		= SYSCTL_TWO,
2157 	},
2158 };
2159 
init_fs_exec_sysctls(void)2160 static int __init init_fs_exec_sysctls(void)
2161 {
2162 	register_sysctl_init("fs", fs_exec_sysctls);
2163 	return 0;
2164 }
2165 
2166 fs_initcall(init_fs_exec_sysctls);
2167 #endif /* CONFIG_SYSCTL */
2168 
2169 #ifdef CONFIG_EXEC_KUNIT_TEST
2170 #include "tests/exec_kunit.c"
2171 #endif
2172