1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3   File: fs/xattr.c
4 
5   Extended attribute handling.
6 
7   Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
8   Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
9   Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
10  */
11 #include <linux/fs.h>
12 #include <linux/slab.h>
13 #include <linux/file.h>
14 #include <linux/xattr.h>
15 #include <linux/mount.h>
16 #include <linux/namei.h>
17 #include <linux/security.h>
18 #include <linux/evm.h>
19 #include <linux/syscalls.h>
20 #include <linux/export.h>
21 #include <linux/fsnotify.h>
22 #include <linux/audit.h>
23 #include <linux/vmalloc.h>
24 #include <linux/posix_acl_xattr.h>
25 
26 #include <linux/uaccess.h>
27 
28 static const char *
strcmp_prefix(const char * a,const char * a_prefix)29 strcmp_prefix(const char *a, const char *a_prefix)
30 {
31 	while (*a_prefix && *a == *a_prefix) {
32 		a++;
33 		a_prefix++;
34 	}
35 	return *a_prefix ? NULL : a;
36 }
37 
38 /*
39  * In order to implement different sets of xattr operations for each xattr
40  * prefix, a filesystem should create a null-terminated array of struct
41  * xattr_handler (one for each prefix) and hang a pointer to it off of the
42  * s_xattr field of the superblock.
43  */
44 #define for_each_xattr_handler(handlers, handler)		\
45 	if (handlers)						\
46 		for ((handler) = *(handlers)++;			\
47 			(handler) != NULL;			\
48 			(handler) = *(handlers)++)
49 
50 /*
51  * Find the xattr_handler with the matching prefix.
52  */
53 static const struct xattr_handler *
xattr_resolve_name(struct inode * inode,const char ** name)54 xattr_resolve_name(struct inode *inode, const char **name)
55 {
56 	const struct xattr_handler **handlers = inode->i_sb->s_xattr;
57 	const struct xattr_handler *handler;
58 
59 	if (!(inode->i_opflags & IOP_XATTR)) {
60 		if (unlikely(is_bad_inode(inode)))
61 			return ERR_PTR(-EIO);
62 		return ERR_PTR(-EOPNOTSUPP);
63 	}
64 	for_each_xattr_handler(handlers, handler) {
65 		const char *n;
66 
67 		n = strcmp_prefix(*name, xattr_prefix(handler));
68 		if (n) {
69 			if (!handler->prefix ^ !*n) {
70 				if (*n)
71 					continue;
72 				return ERR_PTR(-EINVAL);
73 			}
74 			*name = n;
75 			return handler;
76 		}
77 	}
78 	return ERR_PTR(-EOPNOTSUPP);
79 }
80 
81 /*
82  * Check permissions for extended attribute access.  This is a bit complicated
83  * because different namespaces have very different rules.
84  */
85 static int
xattr_permission(struct inode * inode,const char * name,int mask)86 xattr_permission(struct inode *inode, const char *name, int mask)
87 {
88 	/*
89 	 * We can never set or remove an extended attribute on a read-only
90 	 * filesystem  or on an immutable / append-only inode.
91 	 */
92 	if (mask & MAY_WRITE) {
93 		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
94 			return -EPERM;
95 		/*
96 		 * Updating an xattr will likely cause i_uid and i_gid
97 		 * to be writen back improperly if their true value is
98 		 * unknown to the vfs.
99 		 */
100 		if (HAS_UNMAPPED_ID(inode))
101 			return -EPERM;
102 	}
103 
104 	/*
105 	 * No restriction for security.* and system.* from the VFS.  Decision
106 	 * on these is left to the underlying filesystem / security module.
107 	 */
108 	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
109 	    !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
110 		return 0;
111 
112 	/*
113 	 * The trusted.* namespace can only be accessed by privileged users.
114 	 */
115 	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
116 		if (!capable(CAP_SYS_ADMIN))
117 			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
118 		return 0;
119 	}
120 
121 	/*
122 	 * In the user.* namespace, only regular files and directories can have
123 	 * extended attributes. For sticky directories, only the owner and
124 	 * privileged users can write attributes.
125 	 */
126 	if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
127 		if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
128 			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
129 		if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
130 		    (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
131 			return -EPERM;
132 	}
133 
134 	return inode_permission(inode, mask);
135 }
136 
137 /*
138  * Look for any handler that deals with the specified namespace.
139  */
140 int
xattr_supported_namespace(struct inode * inode,const char * prefix)141 xattr_supported_namespace(struct inode *inode, const char *prefix)
142 {
143 	const struct xattr_handler **handlers = inode->i_sb->s_xattr;
144 	const struct xattr_handler *handler;
145 	size_t preflen;
146 
147 	if (!(inode->i_opflags & IOP_XATTR)) {
148 		if (unlikely(is_bad_inode(inode)))
149 			return -EIO;
150 		return -EOPNOTSUPP;
151 	}
152 
153 	preflen = strlen(prefix);
154 
155 	for_each_xattr_handler(handlers, handler) {
156 		if (!strncmp(xattr_prefix(handler), prefix, preflen))
157 			return 0;
158 	}
159 
160 	return -EOPNOTSUPP;
161 }
162 EXPORT_SYMBOL(xattr_supported_namespace);
163 
164 int
__vfs_setxattr(struct dentry * dentry,struct inode * inode,const char * name,const void * value,size_t size,int flags)165 __vfs_setxattr(struct dentry *dentry, struct inode *inode, const char *name,
166 	       const void *value, size_t size, int flags)
167 {
168 	const struct xattr_handler *handler;
169 
170 	handler = xattr_resolve_name(inode, &name);
171 	if (IS_ERR(handler))
172 		return PTR_ERR(handler);
173 	if (!handler->set)
174 		return -EOPNOTSUPP;
175 	if (size == 0)
176 		value = "";  /* empty EA, do not remove */
177 	return handler->set(handler, dentry, inode, name, value, size, flags);
178 }
179 EXPORT_SYMBOL(__vfs_setxattr);
180 
181 /**
182  *  __vfs_setxattr_noperm - perform setxattr operation without performing
183  *  permission checks.
184  *
185  *  @dentry - object to perform setxattr on
186  *  @name - xattr name to set
187  *  @value - value to set @name to
188  *  @size - size of @value
189  *  @flags - flags to pass into filesystem operations
190  *
191  *  returns the result of the internal setxattr or setsecurity operations.
192  *
193  *  This function requires the caller to lock the inode's i_mutex before it
194  *  is executed. It also assumes that the caller will make the appropriate
195  *  permission checks.
196  */
__vfs_setxattr_noperm(struct dentry * dentry,const char * name,const void * value,size_t size,int flags)197 int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
198 		const void *value, size_t size, int flags)
199 {
200 	struct inode *inode = dentry->d_inode;
201 	int error = -EAGAIN;
202 	int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
203 				   XATTR_SECURITY_PREFIX_LEN);
204 
205 	if (issec)
206 		inode->i_flags &= ~S_NOSEC;
207 	if (inode->i_opflags & IOP_XATTR) {
208 		error = __vfs_setxattr(dentry, inode, name, value, size, flags);
209 		if (!error) {
210 			fsnotify_xattr(dentry);
211 			security_inode_post_setxattr(dentry, name, value,
212 						     size, flags);
213 		}
214 	} else {
215 		if (unlikely(is_bad_inode(inode)))
216 			return -EIO;
217 	}
218 	if (error == -EAGAIN) {
219 		error = -EOPNOTSUPP;
220 
221 		if (issec) {
222 			const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
223 
224 			error = security_inode_setsecurity(inode, suffix, value,
225 							   size, flags);
226 			if (!error)
227 				fsnotify_xattr(dentry);
228 		}
229 	}
230 
231 	return error;
232 }
233 
234 /**
235  * __vfs_setxattr_locked - set an extended attribute while holding the inode
236  * lock
237  *
238  *  @dentry: object to perform setxattr on
239  *  @name: xattr name to set
240  *  @value: value to set @name to
241  *  @size: size of @value
242  *  @flags: flags to pass into filesystem operations
243  *  @delegated_inode: on return, will contain an inode pointer that
244  *  a delegation was broken on, NULL if none.
245  */
246 int
__vfs_setxattr_locked(struct dentry * dentry,const char * name,const void * value,size_t size,int flags,struct inode ** delegated_inode)247 __vfs_setxattr_locked(struct dentry *dentry, const char *name,
248 		const void *value, size_t size, int flags,
249 		struct inode **delegated_inode)
250 {
251 	struct inode *inode = dentry->d_inode;
252 	int error;
253 
254 	error = xattr_permission(inode, name, MAY_WRITE);
255 	if (error)
256 		return error;
257 
258 	error = security_inode_setxattr(dentry, name, value, size, flags);
259 	if (error)
260 		goto out;
261 
262 	error = try_break_deleg(inode, delegated_inode);
263 	if (error)
264 		goto out;
265 
266 	error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
267 
268 out:
269 	return error;
270 }
271 EXPORT_SYMBOL_GPL(__vfs_setxattr_locked);
272 
273 int
vfs_setxattr(struct dentry * dentry,const char * name,const void * value,size_t size,int flags)274 vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
275 		size_t size, int flags)
276 {
277 	struct inode *inode = dentry->d_inode;
278 	struct inode *delegated_inode = NULL;
279 	int error;
280 
281 retry_deleg:
282 	inode_lock(inode);
283 	error = __vfs_setxattr_locked(dentry, name, value, size, flags,
284 	    &delegated_inode);
285 	inode_unlock(inode);
286 
287 	if (delegated_inode) {
288 		error = break_deleg_wait(&delegated_inode);
289 		if (!error)
290 			goto retry_deleg;
291 	}
292 	return error;
293 }
294 EXPORT_SYMBOL_GPL(vfs_setxattr);
295 
296 static ssize_t
xattr_getsecurity(struct inode * inode,const char * name,void * value,size_t size)297 xattr_getsecurity(struct inode *inode, const char *name, void *value,
298 			size_t size)
299 {
300 	void *buffer = NULL;
301 	ssize_t len;
302 
303 	if (!value || !size) {
304 		len = security_inode_getsecurity(inode, name, &buffer, false);
305 		goto out_noalloc;
306 	}
307 
308 	len = security_inode_getsecurity(inode, name, &buffer, true);
309 	if (len < 0)
310 		return len;
311 	if (size < len) {
312 		len = -ERANGE;
313 		goto out;
314 	}
315 	memcpy(value, buffer, len);
316 out:
317 	kfree(buffer);
318 out_noalloc:
319 	return len;
320 }
321 
322 /*
323  * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
324  *
325  * Allocate memory, if not already allocated, or re-allocate correct size,
326  * before retrieving the extended attribute.
327  *
328  * Returns the result of alloc, if failed, or the getxattr operation.
329  */
330 ssize_t
vfs_getxattr_alloc(struct dentry * dentry,const char * name,char ** xattr_value,size_t xattr_size,gfp_t flags)331 vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
332 		   size_t xattr_size, gfp_t flags)
333 {
334 	const struct xattr_handler *handler;
335 	struct inode *inode = dentry->d_inode;
336 	char *value = *xattr_value;
337 	int error;
338 
339 	error = xattr_permission(inode, name, MAY_READ);
340 	if (error)
341 		return error;
342 
343 	handler = xattr_resolve_name(inode, &name);
344 	if (IS_ERR(handler))
345 		return PTR_ERR(handler);
346 	if (!handler->get)
347 		return -EOPNOTSUPP;
348 	error = handler->get(handler, dentry, inode, name, NULL, 0);
349 	if (error < 0)
350 		return error;
351 
352 	if (!value || (error > xattr_size)) {
353 		value = krealloc(*xattr_value, error + 1, flags);
354 		if (!value)
355 			return -ENOMEM;
356 		memset(value, 0, error + 1);
357 	}
358 
359 	error = handler->get(handler, dentry, inode, name, value, error);
360 	*xattr_value = value;
361 	return error;
362 }
363 
364 ssize_t
__vfs_getxattr(struct dentry * dentry,struct inode * inode,const char * name,void * value,size_t size)365 __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
366 	       void *value, size_t size)
367 {
368 	const struct xattr_handler *handler;
369 
370 	handler = xattr_resolve_name(inode, &name);
371 	if (IS_ERR(handler))
372 		return PTR_ERR(handler);
373 	if (!handler->get)
374 		return -EOPNOTSUPP;
375 	return handler->get(handler, dentry, inode, name, value, size);
376 }
377 EXPORT_SYMBOL(__vfs_getxattr);
378 
379 ssize_t
vfs_getxattr(struct dentry * dentry,const char * name,void * value,size_t size)380 vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
381 {
382 	struct inode *inode = dentry->d_inode;
383 	int error;
384 
385 	error = xattr_permission(inode, name, MAY_READ);
386 	if (error)
387 		return error;
388 
389 	error = security_inode_getxattr(dentry, name);
390 	if (error)
391 		return error;
392 
393 	if (!strncmp(name, XATTR_SECURITY_PREFIX,
394 				XATTR_SECURITY_PREFIX_LEN)) {
395 		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
396 		int ret = xattr_getsecurity(inode, suffix, value, size);
397 		/*
398 		 * Only overwrite the return value if a security module
399 		 * is actually active.
400 		 */
401 		if (ret == -EOPNOTSUPP)
402 			goto nolsm;
403 		return ret;
404 	}
405 nolsm:
406 	return __vfs_getxattr(dentry, inode, name, value, size);
407 }
408 EXPORT_SYMBOL_GPL(vfs_getxattr);
409 
410 ssize_t
vfs_listxattr(struct dentry * dentry,char * list,size_t size)411 vfs_listxattr(struct dentry *dentry, char *list, size_t size)
412 {
413 	struct inode *inode = d_inode(dentry);
414 	ssize_t error;
415 
416 	error = security_inode_listxattr(dentry);
417 	if (error)
418 		return error;
419 	if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
420 		error = inode->i_op->listxattr(dentry, list, size);
421 	} else {
422 		error = security_inode_listsecurity(inode, list, size);
423 		if (size && error > size)
424 			error = -ERANGE;
425 	}
426 	return error;
427 }
428 EXPORT_SYMBOL_GPL(vfs_listxattr);
429 
430 int
__vfs_removexattr(struct dentry * dentry,const char * name)431 __vfs_removexattr(struct dentry *dentry, const char *name)
432 {
433 	struct inode *inode = d_inode(dentry);
434 	const struct xattr_handler *handler;
435 
436 	handler = xattr_resolve_name(inode, &name);
437 	if (IS_ERR(handler))
438 		return PTR_ERR(handler);
439 	if (!handler->set)
440 		return -EOPNOTSUPP;
441 	return handler->set(handler, dentry, inode, name, NULL, 0, XATTR_REPLACE);
442 }
443 EXPORT_SYMBOL(__vfs_removexattr);
444 
445 /**
446  * __vfs_removexattr_locked - set an extended attribute while holding the inode
447  * lock
448  *
449  *  @dentry: object to perform setxattr on
450  *  @name: name of xattr to remove
451  *  @delegated_inode: on return, will contain an inode pointer that
452  *  a delegation was broken on, NULL if none.
453  */
454 int
__vfs_removexattr_locked(struct dentry * dentry,const char * name,struct inode ** delegated_inode)455 __vfs_removexattr_locked(struct dentry *dentry, const char *name,
456 		struct inode **delegated_inode)
457 {
458 	struct inode *inode = dentry->d_inode;
459 	int error;
460 
461 	error = xattr_permission(inode, name, MAY_WRITE);
462 	if (error)
463 		return error;
464 
465 	error = security_inode_removexattr(dentry, name);
466 	if (error)
467 		goto out;
468 
469 	error = try_break_deleg(inode, delegated_inode);
470 	if (error)
471 		goto out;
472 
473 	error = __vfs_removexattr(dentry, name);
474 
475 	if (!error) {
476 		fsnotify_xattr(dentry);
477 		evm_inode_post_removexattr(dentry, name);
478 	}
479 
480 out:
481 	return error;
482 }
483 EXPORT_SYMBOL_GPL(__vfs_removexattr_locked);
484 
485 int
vfs_removexattr(struct dentry * dentry,const char * name)486 vfs_removexattr(struct dentry *dentry, const char *name)
487 {
488 	struct inode *inode = dentry->d_inode;
489 	struct inode *delegated_inode = NULL;
490 	int error;
491 
492 retry_deleg:
493 	inode_lock(inode);
494 	error = __vfs_removexattr_locked(dentry, name, &delegated_inode);
495 	inode_unlock(inode);
496 
497 	if (delegated_inode) {
498 		error = break_deleg_wait(&delegated_inode);
499 		if (!error)
500 			goto retry_deleg;
501 	}
502 
503 	return error;
504 }
505 EXPORT_SYMBOL_GPL(vfs_removexattr);
506 
507 /*
508  * Extended attribute SET operations
509  */
510 static long
setxattr(struct dentry * d,const char __user * name,const void __user * value,size_t size,int flags)511 setxattr(struct dentry *d, const char __user *name, const void __user *value,
512 	 size_t size, int flags)
513 {
514 	int error;
515 	void *kvalue = NULL;
516 	char kname[XATTR_NAME_MAX + 1];
517 
518 	if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
519 		return -EINVAL;
520 
521 	error = strncpy_from_user(kname, name, sizeof(kname));
522 	if (error == 0 || error == sizeof(kname))
523 		error = -ERANGE;
524 	if (error < 0)
525 		return error;
526 
527 	if (size) {
528 		if (size > XATTR_SIZE_MAX)
529 			return -E2BIG;
530 		kvalue = kvmalloc(size, GFP_KERNEL);
531 		if (!kvalue)
532 			return -ENOMEM;
533 		if (copy_from_user(kvalue, value, size)) {
534 			error = -EFAULT;
535 			goto out;
536 		}
537 		if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
538 		    (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
539 			posix_acl_fix_xattr_from_user(kvalue, size);
540 		else if (strcmp(kname, XATTR_NAME_CAPS) == 0) {
541 			error = cap_convert_nscap(d, &kvalue, size);
542 			if (error < 0)
543 				goto out;
544 			size = error;
545 		}
546 	}
547 
548 	error = vfs_setxattr(d, kname, kvalue, size, flags);
549 out:
550 	kvfree(kvalue);
551 
552 	return error;
553 }
554 
path_setxattr(const char __user * pathname,const char __user * name,const void __user * value,size_t size,int flags,unsigned int lookup_flags)555 static int path_setxattr(const char __user *pathname,
556 			 const char __user *name, const void __user *value,
557 			 size_t size, int flags, unsigned int lookup_flags)
558 {
559 	struct path path;
560 	int error;
561 retry:
562 	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
563 	if (error)
564 		return error;
565 	error = mnt_want_write(path.mnt);
566 	if (!error) {
567 		error = setxattr(path.dentry, name, value, size, flags);
568 		mnt_drop_write(path.mnt);
569 	}
570 	path_put(&path);
571 	if (retry_estale(error, lookup_flags)) {
572 		lookup_flags |= LOOKUP_REVAL;
573 		goto retry;
574 	}
575 	return error;
576 }
577 
SYSCALL_DEFINE5(setxattr,const char __user *,pathname,const char __user *,name,const void __user *,value,size_t,size,int,flags)578 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
579 		const char __user *, name, const void __user *, value,
580 		size_t, size, int, flags)
581 {
582 	return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
583 }
584 
SYSCALL_DEFINE5(lsetxattr,const char __user *,pathname,const char __user *,name,const void __user *,value,size_t,size,int,flags)585 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
586 		const char __user *, name, const void __user *, value,
587 		size_t, size, int, flags)
588 {
589 	return path_setxattr(pathname, name, value, size, flags, 0);
590 }
591 
SYSCALL_DEFINE5(fsetxattr,int,fd,const char __user *,name,const void __user *,value,size_t,size,int,flags)592 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
593 		const void __user *,value, size_t, size, int, flags)
594 {
595 	struct fd f = fdget(fd);
596 	int error = -EBADF;
597 
598 	if (!f.file)
599 		return error;
600 	audit_file(f.file);
601 	error = mnt_want_write_file(f.file);
602 	if (!error) {
603 		error = setxattr(f.file->f_path.dentry, name, value, size, flags);
604 		mnt_drop_write_file(f.file);
605 	}
606 	fdput(f);
607 	return error;
608 }
609 
610 /*
611  * Extended attribute GET operations
612  */
613 static ssize_t
getxattr(struct dentry * d,const char __user * name,void __user * value,size_t size)614 getxattr(struct dentry *d, const char __user *name, void __user *value,
615 	 size_t size)
616 {
617 	ssize_t error;
618 	void *kvalue = NULL;
619 	char kname[XATTR_NAME_MAX + 1];
620 
621 	error = strncpy_from_user(kname, name, sizeof(kname));
622 	if (error == 0 || error == sizeof(kname))
623 		error = -ERANGE;
624 	if (error < 0)
625 		return error;
626 
627 	if (size) {
628 		if (size > XATTR_SIZE_MAX)
629 			size = XATTR_SIZE_MAX;
630 		kvalue = kvzalloc(size, GFP_KERNEL);
631 		if (!kvalue)
632 			return -ENOMEM;
633 	}
634 
635 	error = vfs_getxattr(d, kname, kvalue, size);
636 	if (error > 0) {
637 		if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
638 		    (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
639 			posix_acl_fix_xattr_to_user(kvalue, error);
640 		if (size && copy_to_user(value, kvalue, error))
641 			error = -EFAULT;
642 	} else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
643 		/* The file system tried to returned a value bigger
644 		   than XATTR_SIZE_MAX bytes. Not possible. */
645 		error = -E2BIG;
646 	}
647 
648 	kvfree(kvalue);
649 
650 	return error;
651 }
652 
path_getxattr(const char __user * pathname,const char __user * name,void __user * value,size_t size,unsigned int lookup_flags)653 static ssize_t path_getxattr(const char __user *pathname,
654 			     const char __user *name, void __user *value,
655 			     size_t size, unsigned int lookup_flags)
656 {
657 	struct path path;
658 	ssize_t error;
659 retry:
660 	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
661 	if (error)
662 		return error;
663 	error = getxattr(path.dentry, name, value, size);
664 	path_put(&path);
665 	if (retry_estale(error, lookup_flags)) {
666 		lookup_flags |= LOOKUP_REVAL;
667 		goto retry;
668 	}
669 	return error;
670 }
671 
SYSCALL_DEFINE4(getxattr,const char __user *,pathname,const char __user *,name,void __user *,value,size_t,size)672 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
673 		const char __user *, name, void __user *, value, size_t, size)
674 {
675 	return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
676 }
677 
SYSCALL_DEFINE4(lgetxattr,const char __user *,pathname,const char __user *,name,void __user *,value,size_t,size)678 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
679 		const char __user *, name, void __user *, value, size_t, size)
680 {
681 	return path_getxattr(pathname, name, value, size, 0);
682 }
683 
SYSCALL_DEFINE4(fgetxattr,int,fd,const char __user *,name,void __user *,value,size_t,size)684 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
685 		void __user *, value, size_t, size)
686 {
687 	struct fd f = fdget(fd);
688 	ssize_t error = -EBADF;
689 
690 	if (!f.file)
691 		return error;
692 	audit_file(f.file);
693 	error = getxattr(f.file->f_path.dentry, name, value, size);
694 	fdput(f);
695 	return error;
696 }
697 
698 /*
699  * Extended attribute LIST operations
700  */
701 static ssize_t
listxattr(struct dentry * d,char __user * list,size_t size)702 listxattr(struct dentry *d, char __user *list, size_t size)
703 {
704 	ssize_t error;
705 	char *klist = NULL;
706 
707 	if (size) {
708 		if (size > XATTR_LIST_MAX)
709 			size = XATTR_LIST_MAX;
710 		klist = kvmalloc(size, GFP_KERNEL);
711 		if (!klist)
712 			return -ENOMEM;
713 	}
714 
715 	error = vfs_listxattr(d, klist, size);
716 	if (error > 0) {
717 		if (size && copy_to_user(list, klist, error))
718 			error = -EFAULT;
719 	} else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
720 		/* The file system tried to returned a list bigger
721 		   than XATTR_LIST_MAX bytes. Not possible. */
722 		error = -E2BIG;
723 	}
724 
725 	kvfree(klist);
726 
727 	return error;
728 }
729 
path_listxattr(const char __user * pathname,char __user * list,size_t size,unsigned int lookup_flags)730 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
731 			      size_t size, unsigned int lookup_flags)
732 {
733 	struct path path;
734 	ssize_t error;
735 retry:
736 	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
737 	if (error)
738 		return error;
739 	error = listxattr(path.dentry, list, size);
740 	path_put(&path);
741 	if (retry_estale(error, lookup_flags)) {
742 		lookup_flags |= LOOKUP_REVAL;
743 		goto retry;
744 	}
745 	return error;
746 }
747 
SYSCALL_DEFINE3(listxattr,const char __user *,pathname,char __user *,list,size_t,size)748 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
749 		size_t, size)
750 {
751 	return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
752 }
753 
SYSCALL_DEFINE3(llistxattr,const char __user *,pathname,char __user *,list,size_t,size)754 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
755 		size_t, size)
756 {
757 	return path_listxattr(pathname, list, size, 0);
758 }
759 
SYSCALL_DEFINE3(flistxattr,int,fd,char __user *,list,size_t,size)760 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
761 {
762 	struct fd f = fdget(fd);
763 	ssize_t error = -EBADF;
764 
765 	if (!f.file)
766 		return error;
767 	audit_file(f.file);
768 	error = listxattr(f.file->f_path.dentry, list, size);
769 	fdput(f);
770 	return error;
771 }
772 
773 /*
774  * Extended attribute REMOVE operations
775  */
776 static long
removexattr(struct dentry * d,const char __user * name)777 removexattr(struct dentry *d, const char __user *name)
778 {
779 	int error;
780 	char kname[XATTR_NAME_MAX + 1];
781 
782 	error = strncpy_from_user(kname, name, sizeof(kname));
783 	if (error == 0 || error == sizeof(kname))
784 		error = -ERANGE;
785 	if (error < 0)
786 		return error;
787 
788 	return vfs_removexattr(d, kname);
789 }
790 
path_removexattr(const char __user * pathname,const char __user * name,unsigned int lookup_flags)791 static int path_removexattr(const char __user *pathname,
792 			    const char __user *name, unsigned int lookup_flags)
793 {
794 	struct path path;
795 	int error;
796 retry:
797 	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
798 	if (error)
799 		return error;
800 	error = mnt_want_write(path.mnt);
801 	if (!error) {
802 		error = removexattr(path.dentry, name);
803 		mnt_drop_write(path.mnt);
804 	}
805 	path_put(&path);
806 	if (retry_estale(error, lookup_flags)) {
807 		lookup_flags |= LOOKUP_REVAL;
808 		goto retry;
809 	}
810 	return error;
811 }
812 
SYSCALL_DEFINE2(removexattr,const char __user *,pathname,const char __user *,name)813 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
814 		const char __user *, name)
815 {
816 	return path_removexattr(pathname, name, LOOKUP_FOLLOW);
817 }
818 
SYSCALL_DEFINE2(lremovexattr,const char __user *,pathname,const char __user *,name)819 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
820 		const char __user *, name)
821 {
822 	return path_removexattr(pathname, name, 0);
823 }
824 
SYSCALL_DEFINE2(fremovexattr,int,fd,const char __user *,name)825 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
826 {
827 	struct fd f = fdget(fd);
828 	int error = -EBADF;
829 
830 	if (!f.file)
831 		return error;
832 	audit_file(f.file);
833 	error = mnt_want_write_file(f.file);
834 	if (!error) {
835 		error = removexattr(f.file->f_path.dentry, name);
836 		mnt_drop_write_file(f.file);
837 	}
838 	fdput(f);
839 	return error;
840 }
841 
842 /*
843  * Combine the results of the list() operation from every xattr_handler in the
844  * list.
845  */
846 ssize_t
generic_listxattr(struct dentry * dentry,char * buffer,size_t buffer_size)847 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
848 {
849 	const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
850 	unsigned int size = 0;
851 
852 	if (!buffer) {
853 		for_each_xattr_handler(handlers, handler) {
854 			if (!handler->name ||
855 			    (handler->list && !handler->list(dentry)))
856 				continue;
857 			size += strlen(handler->name) + 1;
858 		}
859 	} else {
860 		char *buf = buffer;
861 		size_t len;
862 
863 		for_each_xattr_handler(handlers, handler) {
864 			if (!handler->name ||
865 			    (handler->list && !handler->list(dentry)))
866 				continue;
867 			len = strlen(handler->name);
868 			if (len + 1 > buffer_size)
869 				return -ERANGE;
870 			memcpy(buf, handler->name, len + 1);
871 			buf += len + 1;
872 			buffer_size -= len + 1;
873 		}
874 		size = buf - buffer;
875 	}
876 	return size;
877 }
878 EXPORT_SYMBOL(generic_listxattr);
879 
880 /**
881  * xattr_full_name  -  Compute full attribute name from suffix
882  *
883  * @handler:	handler of the xattr_handler operation
884  * @name:	name passed to the xattr_handler operation
885  *
886  * The get and set xattr handler operations are called with the remainder of
887  * the attribute name after skipping the handler's prefix: for example, "foo"
888  * is passed to the get operation of a handler with prefix "user." to get
889  * attribute "user.foo".  The full name is still "there" in the name though.
890  *
891  * Note: the list xattr handler operation when called from the vfs is passed a
892  * NULL name; some file systems use this operation internally, with varying
893  * semantics.
894  */
xattr_full_name(const struct xattr_handler * handler,const char * name)895 const char *xattr_full_name(const struct xattr_handler *handler,
896 			    const char *name)
897 {
898 	size_t prefix_len = strlen(xattr_prefix(handler));
899 
900 	return name - prefix_len;
901 }
902 EXPORT_SYMBOL(xattr_full_name);
903 
904 /*
905  * Allocate new xattr and copy in the value; but leave the name to callers.
906  */
simple_xattr_alloc(const void * value,size_t size)907 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
908 {
909 	struct simple_xattr *new_xattr;
910 	size_t len;
911 
912 	/* wrap around? */
913 	len = sizeof(*new_xattr) + size;
914 	if (len < sizeof(*new_xattr))
915 		return NULL;
916 
917 	new_xattr = kvmalloc(len, GFP_KERNEL);
918 	if (!new_xattr)
919 		return NULL;
920 
921 	new_xattr->size = size;
922 	memcpy(new_xattr->value, value, size);
923 	return new_xattr;
924 }
925 
926 /*
927  * xattr GET operation for in-memory/pseudo filesystems
928  */
simple_xattr_get(struct simple_xattrs * xattrs,const char * name,void * buffer,size_t size)929 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
930 		     void *buffer, size_t size)
931 {
932 	struct simple_xattr *xattr;
933 	int ret = -ENODATA;
934 
935 	spin_lock(&xattrs->lock);
936 	list_for_each_entry(xattr, &xattrs->head, list) {
937 		if (strcmp(name, xattr->name))
938 			continue;
939 
940 		ret = xattr->size;
941 		if (buffer) {
942 			if (size < xattr->size)
943 				ret = -ERANGE;
944 			else
945 				memcpy(buffer, xattr->value, xattr->size);
946 		}
947 		break;
948 	}
949 	spin_unlock(&xattrs->lock);
950 	return ret;
951 }
952 
953 /**
954  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
955  * @xattrs: target simple_xattr list
956  * @name: name of the extended attribute
957  * @value: value of the xattr. If %NULL, will remove the attribute.
958  * @size: size of the new xattr
959  * @flags: %XATTR_{CREATE|REPLACE}
960  * @removed_size: returns size of the removed xattr, -1 if none removed
961  *
962  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
963  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
964  * otherwise, fails with -ENODATA.
965  *
966  * Returns 0 on success, -errno on failure.
967  */
simple_xattr_set(struct simple_xattrs * xattrs,const char * name,const void * value,size_t size,int flags,ssize_t * removed_size)968 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
969 		     const void *value, size_t size, int flags,
970 		     ssize_t *removed_size)
971 {
972 	struct simple_xattr *xattr;
973 	struct simple_xattr *new_xattr = NULL;
974 	int err = 0;
975 
976 	if (removed_size)
977 		*removed_size = -1;
978 
979 	/* value == NULL means remove */
980 	if (value) {
981 		new_xattr = simple_xattr_alloc(value, size);
982 		if (!new_xattr)
983 			return -ENOMEM;
984 
985 		new_xattr->name = kstrdup(name, GFP_KERNEL);
986 		if (!new_xattr->name) {
987 			kvfree(new_xattr);
988 			return -ENOMEM;
989 		}
990 	}
991 
992 	spin_lock(&xattrs->lock);
993 	list_for_each_entry(xattr, &xattrs->head, list) {
994 		if (!strcmp(name, xattr->name)) {
995 			if (flags & XATTR_CREATE) {
996 				xattr = new_xattr;
997 				err = -EEXIST;
998 			} else if (new_xattr) {
999 				list_replace(&xattr->list, &new_xattr->list);
1000 				if (removed_size)
1001 					*removed_size = xattr->size;
1002 			} else {
1003 				list_del(&xattr->list);
1004 				if (removed_size)
1005 					*removed_size = xattr->size;
1006 			}
1007 			goto out;
1008 		}
1009 	}
1010 	if (flags & XATTR_REPLACE) {
1011 		xattr = new_xattr;
1012 		err = -ENODATA;
1013 	} else {
1014 		list_add(&new_xattr->list, &xattrs->head);
1015 		xattr = NULL;
1016 	}
1017 out:
1018 	spin_unlock(&xattrs->lock);
1019 	if (xattr) {
1020 		kfree(xattr->name);
1021 		kvfree(xattr);
1022 	}
1023 	return err;
1024 
1025 }
1026 
xattr_is_trusted(const char * name)1027 static bool xattr_is_trusted(const char *name)
1028 {
1029 	return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
1030 }
1031 
xattr_list_one(char ** buffer,ssize_t * remaining_size,const char * name)1032 static int xattr_list_one(char **buffer, ssize_t *remaining_size,
1033 			  const char *name)
1034 {
1035 	size_t len = strlen(name) + 1;
1036 	if (*buffer) {
1037 		if (*remaining_size < len)
1038 			return -ERANGE;
1039 		memcpy(*buffer, name, len);
1040 		*buffer += len;
1041 	}
1042 	*remaining_size -= len;
1043 	return 0;
1044 }
1045 
1046 /*
1047  * xattr LIST operation for in-memory/pseudo filesystems
1048  */
simple_xattr_list(struct inode * inode,struct simple_xattrs * xattrs,char * buffer,size_t size)1049 ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
1050 			  char *buffer, size_t size)
1051 {
1052 	bool trusted = capable(CAP_SYS_ADMIN);
1053 	struct simple_xattr *xattr;
1054 	ssize_t remaining_size = size;
1055 	int err = 0;
1056 
1057 #ifdef CONFIG_FS_POSIX_ACL
1058 	if (IS_POSIXACL(inode)) {
1059 		if (inode->i_acl) {
1060 			err = xattr_list_one(&buffer, &remaining_size,
1061 					     XATTR_NAME_POSIX_ACL_ACCESS);
1062 			if (err)
1063 				return err;
1064 		}
1065 		if (inode->i_default_acl) {
1066 			err = xattr_list_one(&buffer, &remaining_size,
1067 					     XATTR_NAME_POSIX_ACL_DEFAULT);
1068 			if (err)
1069 				return err;
1070 		}
1071 	}
1072 #endif
1073 
1074 	spin_lock(&xattrs->lock);
1075 	list_for_each_entry(xattr, &xattrs->head, list) {
1076 		/* skip "trusted." attributes for unprivileged callers */
1077 		if (!trusted && xattr_is_trusted(xattr->name))
1078 			continue;
1079 
1080 		err = xattr_list_one(&buffer, &remaining_size, xattr->name);
1081 		if (err)
1082 			break;
1083 	}
1084 	spin_unlock(&xattrs->lock);
1085 
1086 	return err ? err : size - remaining_size;
1087 }
1088 
1089 /*
1090  * Adds an extended attribute to the list
1091  */
simple_xattr_list_add(struct simple_xattrs * xattrs,struct simple_xattr * new_xattr)1092 void simple_xattr_list_add(struct simple_xattrs *xattrs,
1093 			   struct simple_xattr *new_xattr)
1094 {
1095 	spin_lock(&xattrs->lock);
1096 	list_add(&new_xattr->list, &xattrs->head);
1097 	spin_unlock(&xattrs->lock);
1098 }
1099