• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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 #include "internal.h"
29 
30 static const char *
strcmp_prefix(const char * a,const char * a_prefix)31 strcmp_prefix(const char *a, const char *a_prefix)
32 {
33 	while (*a_prefix && *a == *a_prefix) {
34 		a++;
35 		a_prefix++;
36 	}
37 	return *a_prefix ? NULL : a;
38 }
39 
40 /*
41  * In order to implement different sets of xattr operations for each xattr
42  * prefix, a filesystem should create a null-terminated array of struct
43  * xattr_handler (one for each prefix) and hang a pointer to it off of the
44  * s_xattr field of the superblock.
45  */
46 #define for_each_xattr_handler(handlers, handler)		\
47 	if (handlers)						\
48 		for ((handler) = *(handlers)++;			\
49 			(handler) != NULL;			\
50 			(handler) = *(handlers)++)
51 
52 /*
53  * Find the xattr_handler with the matching prefix.
54  */
55 static const struct xattr_handler *
xattr_resolve_name(struct inode * inode,const char ** name)56 xattr_resolve_name(struct inode *inode, const char **name)
57 {
58 	const struct xattr_handler **handlers = inode->i_sb->s_xattr;
59 	const struct xattr_handler *handler;
60 
61 	if (!(inode->i_opflags & IOP_XATTR)) {
62 		if (unlikely(is_bad_inode(inode)))
63 			return ERR_PTR(-EIO);
64 		return ERR_PTR(-EOPNOTSUPP);
65 	}
66 	for_each_xattr_handler(handlers, handler) {
67 		const char *n;
68 
69 		n = strcmp_prefix(*name, xattr_prefix(handler));
70 		if (n) {
71 			if (!handler->prefix ^ !*n) {
72 				if (*n)
73 					continue;
74 				return ERR_PTR(-EINVAL);
75 			}
76 			*name = n;
77 			return handler;
78 		}
79 	}
80 	return ERR_PTR(-EOPNOTSUPP);
81 }
82 
83 /*
84  * Check permissions for extended attribute access.  This is a bit complicated
85  * because different namespaces have very different rules.
86  */
87 static int
xattr_permission(struct user_namespace * mnt_userns,struct inode * inode,const char * name,int mask)88 xattr_permission(struct user_namespace *mnt_userns, struct inode *inode,
89 		 const char *name, int mask)
90 {
91 	/*
92 	 * We can never set or remove an extended attribute on a read-only
93 	 * filesystem  or on an immutable / append-only inode.
94 	 */
95 	if (mask & MAY_WRITE) {
96 		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
97 			return -EPERM;
98 		/*
99 		 * Updating an xattr will likely cause i_uid and i_gid
100 		 * to be writen back improperly if their true value is
101 		 * unknown to the vfs.
102 		 */
103 		if (HAS_UNMAPPED_ID(mnt_userns, inode))
104 			return -EPERM;
105 	}
106 
107 	/*
108 	 * No restriction for security.* and system.* from the VFS.  Decision
109 	 * on these is left to the underlying filesystem / security module.
110 	 */
111 	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
112 	    !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
113 		return 0;
114 
115 	/*
116 	 * The trusted.* namespace can only be accessed by privileged users.
117 	 */
118 	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
119 		if (!capable(CAP_SYS_ADMIN))
120 			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
121 		return 0;
122 	}
123 
124 	/*
125 	 * In the user.* namespace, only regular files and directories can have
126 	 * extended attributes. For sticky directories, only the owner and
127 	 * privileged users can write attributes.
128 	 */
129 	if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
130 		if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
131 			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
132 		if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
133 		    (mask & MAY_WRITE) &&
134 		    !inode_owner_or_capable(mnt_userns, inode))
135 			return -EPERM;
136 	}
137 
138 	return inode_permission(mnt_userns, inode, mask);
139 }
140 
141 /*
142  * Look for any handler that deals with the specified namespace.
143  */
144 int
xattr_supported_namespace(struct inode * inode,const char * prefix)145 xattr_supported_namespace(struct inode *inode, const char *prefix)
146 {
147 	const struct xattr_handler **handlers = inode->i_sb->s_xattr;
148 	const struct xattr_handler *handler;
149 	size_t preflen;
150 
151 	if (!(inode->i_opflags & IOP_XATTR)) {
152 		if (unlikely(is_bad_inode(inode)))
153 			return -EIO;
154 		return -EOPNOTSUPP;
155 	}
156 
157 	preflen = strlen(prefix);
158 
159 	for_each_xattr_handler(handlers, handler) {
160 		if (!strncmp(xattr_prefix(handler), prefix, preflen))
161 			return 0;
162 	}
163 
164 	return -EOPNOTSUPP;
165 }
166 EXPORT_SYMBOL(xattr_supported_namespace);
167 
168 int
__vfs_setxattr(struct user_namespace * mnt_userns,struct dentry * dentry,struct inode * inode,const char * name,const void * value,size_t size,int flags)169 __vfs_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
170 	       struct inode *inode, const char *name, const void *value,
171 	       size_t size, int flags)
172 {
173 	const struct xattr_handler *handler;
174 
175 	handler = xattr_resolve_name(inode, &name);
176 	if (IS_ERR(handler))
177 		return PTR_ERR(handler);
178 	if (!handler->set)
179 		return -EOPNOTSUPP;
180 	if (size == 0)
181 		value = "";  /* empty EA, do not remove */
182 	return handler->set(handler, mnt_userns, dentry, inode, name, value,
183 			    size, flags);
184 }
185 EXPORT_SYMBOL(__vfs_setxattr);
186 
187 /**
188  *  __vfs_setxattr_noperm - perform setxattr operation without performing
189  *  permission checks.
190  *
191  *  @mnt_userns: user namespace of the mount the inode was found from
192  *  @dentry: object to perform setxattr on
193  *  @name: xattr name to set
194  *  @value: value to set @name to
195  *  @size: size of @value
196  *  @flags: flags to pass into filesystem operations
197  *
198  *  returns the result of the internal setxattr or setsecurity operations.
199  *
200  *  This function requires the caller to lock the inode's i_mutex before it
201  *  is executed. It also assumes that the caller will make the appropriate
202  *  permission checks.
203  */
__vfs_setxattr_noperm(struct user_namespace * mnt_userns,struct dentry * dentry,const char * name,const void * value,size_t size,int flags)204 int __vfs_setxattr_noperm(struct user_namespace *mnt_userns,
205 			  struct dentry *dentry, const char *name,
206 			  const void *value, size_t size, int flags)
207 {
208 	struct inode *inode = dentry->d_inode;
209 	int error = -EAGAIN;
210 	int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
211 				   XATTR_SECURITY_PREFIX_LEN);
212 
213 	if (issec)
214 		inode->i_flags &= ~S_NOSEC;
215 	if (inode->i_opflags & IOP_XATTR) {
216 		error = __vfs_setxattr(mnt_userns, dentry, inode, name, value,
217 				       size, flags);
218 		if (!error) {
219 			fsnotify_xattr(dentry);
220 			security_inode_post_setxattr(dentry, name, value,
221 						     size, flags);
222 		}
223 	} else {
224 		if (unlikely(is_bad_inode(inode)))
225 			return -EIO;
226 	}
227 	if (error == -EAGAIN) {
228 		error = -EOPNOTSUPP;
229 
230 		if (issec) {
231 			const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
232 
233 			error = security_inode_setsecurity(inode, suffix, value,
234 							   size, flags);
235 			if (!error)
236 				fsnotify_xattr(dentry);
237 		}
238 	}
239 
240 	return error;
241 }
242 
243 /**
244  * __vfs_setxattr_locked - set an extended attribute while holding the inode
245  * lock
246  *
247  *  @mnt_userns: user namespace of the mount of the target inode
248  *  @dentry: object to perform setxattr on
249  *  @name: xattr name to set
250  *  @value: value to set @name to
251  *  @size: size of @value
252  *  @flags: flags to pass into filesystem operations
253  *  @delegated_inode: on return, will contain an inode pointer that
254  *  a delegation was broken on, NULL if none.
255  */
256 int
__vfs_setxattr_locked(struct user_namespace * mnt_userns,struct dentry * dentry,const char * name,const void * value,size_t size,int flags,struct inode ** delegated_inode)257 __vfs_setxattr_locked(struct user_namespace *mnt_userns, struct dentry *dentry,
258 		      const char *name, const void *value, size_t size,
259 		      int flags, struct inode **delegated_inode)
260 {
261 	struct inode *inode = dentry->d_inode;
262 	int error;
263 
264 	error = xattr_permission(mnt_userns, inode, name, MAY_WRITE);
265 	if (error)
266 		return error;
267 
268 	error = security_inode_setxattr(mnt_userns, dentry, name, value, size,
269 					flags);
270 	if (error)
271 		goto out;
272 
273 	error = try_break_deleg(inode, delegated_inode);
274 	if (error)
275 		goto out;
276 
277 	error = __vfs_setxattr_noperm(mnt_userns, dentry, name, value,
278 				      size, flags);
279 
280 out:
281 	return error;
282 }
283 EXPORT_SYMBOL_GPL(__vfs_setxattr_locked);
284 
285 int
vfs_setxattr(struct user_namespace * mnt_userns,struct dentry * dentry,const char * name,const void * value,size_t size,int flags)286 vfs_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
287 	     const char *name, const void *value, size_t size, int flags)
288 {
289 	struct inode *inode = dentry->d_inode;
290 	struct inode *delegated_inode = NULL;
291 	const void  *orig_value = value;
292 	int error;
293 
294 	if (size && strcmp(name, XATTR_NAME_CAPS) == 0) {
295 		error = cap_convert_nscap(mnt_userns, dentry, &value, size);
296 		if (error < 0)
297 			return error;
298 		size = error;
299 	}
300 
301 retry_deleg:
302 	inode_lock(inode);
303 	error = __vfs_setxattr_locked(mnt_userns, dentry, name, value, size,
304 				      flags, &delegated_inode);
305 	inode_unlock(inode);
306 
307 	if (delegated_inode) {
308 		error = break_deleg_wait(&delegated_inode);
309 		if (!error)
310 			goto retry_deleg;
311 	}
312 	if (value != orig_value)
313 		kfree(value);
314 
315 	return error;
316 }
317 EXPORT_SYMBOL_NS_GPL(vfs_setxattr, ANDROID_GKI_VFS_EXPORT_ONLY);
318 
319 static ssize_t
xattr_getsecurity(struct user_namespace * mnt_userns,struct inode * inode,const char * name,void * value,size_t size)320 xattr_getsecurity(struct user_namespace *mnt_userns, struct inode *inode,
321 		  const char *name, void *value, size_t size)
322 {
323 	void *buffer = NULL;
324 	ssize_t len;
325 
326 	if (!value || !size) {
327 		len = security_inode_getsecurity(mnt_userns, inode, name,
328 						 &buffer, false);
329 		goto out_noalloc;
330 	}
331 
332 	len = security_inode_getsecurity(mnt_userns, inode, name, &buffer,
333 					 true);
334 	if (len < 0)
335 		return len;
336 	if (size < len) {
337 		len = -ERANGE;
338 		goto out;
339 	}
340 	memcpy(value, buffer, len);
341 out:
342 	kfree(buffer);
343 out_noalloc:
344 	return len;
345 }
346 
347 /*
348  * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
349  *
350  * Allocate memory, if not already allocated, or re-allocate correct size,
351  * before retrieving the extended attribute.
352  *
353  * Returns the result of alloc, if failed, or the getxattr operation.
354  */
355 ssize_t
vfs_getxattr_alloc(struct user_namespace * mnt_userns,struct dentry * dentry,const char * name,char ** xattr_value,size_t xattr_size,gfp_t flags)356 vfs_getxattr_alloc(struct user_namespace *mnt_userns, struct dentry *dentry,
357 		   const char *name, char **xattr_value, size_t xattr_size,
358 		   gfp_t flags)
359 {
360 	const struct xattr_handler *handler;
361 	struct inode *inode = dentry->d_inode;
362 	char *value = *xattr_value;
363 	int error;
364 
365 	error = xattr_permission(mnt_userns, inode, name, MAY_READ);
366 	if (error)
367 		return error;
368 
369 	handler = xattr_resolve_name(inode, &name);
370 	if (IS_ERR(handler))
371 		return PTR_ERR(handler);
372 	if (!handler->get)
373 		return -EOPNOTSUPP;
374 	error = handler->get(handler, dentry, inode, name, NULL, 0);
375 	if (error < 0)
376 		return error;
377 
378 	if (!value || (error > xattr_size)) {
379 		value = krealloc(*xattr_value, error + 1, flags);
380 		if (!value)
381 			return -ENOMEM;
382 		memset(value, 0, error + 1);
383 	}
384 
385 	error = handler->get(handler, dentry, inode, name, value, error);
386 	*xattr_value = value;
387 	return error;
388 }
389 
390 ssize_t
__vfs_getxattr(struct dentry * dentry,struct inode * inode,const char * name,void * value,size_t size)391 __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
392 	       void *value, size_t size)
393 {
394 	const struct xattr_handler *handler;
395 
396 	handler = xattr_resolve_name(inode, &name);
397 	if (IS_ERR(handler))
398 		return PTR_ERR(handler);
399 	if (!handler->get)
400 		return -EOPNOTSUPP;
401 	return handler->get(handler, dentry, inode, name, value, size);
402 }
403 EXPORT_SYMBOL(__vfs_getxattr);
404 
405 ssize_t
vfs_getxattr(struct user_namespace * mnt_userns,struct dentry * dentry,const char * name,void * value,size_t size)406 vfs_getxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
407 	     const char *name, void *value, size_t size)
408 {
409 	struct inode *inode = dentry->d_inode;
410 	int error;
411 
412 	error = xattr_permission(mnt_userns, inode, name, MAY_READ);
413 	if (error)
414 		return error;
415 
416 	error = security_inode_getxattr(dentry, name);
417 	if (error)
418 		return error;
419 
420 	if (!strncmp(name, XATTR_SECURITY_PREFIX,
421 				XATTR_SECURITY_PREFIX_LEN)) {
422 		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
423 		int ret = xattr_getsecurity(mnt_userns, inode, suffix, value,
424 					    size);
425 		/*
426 		 * Only overwrite the return value if a security module
427 		 * is actually active.
428 		 */
429 		if (ret == -EOPNOTSUPP)
430 			goto nolsm;
431 		return ret;
432 	}
433 nolsm:
434 	return __vfs_getxattr(dentry, inode, name, value, size);
435 }
436 EXPORT_SYMBOL_NS_GPL(vfs_getxattr, ANDROID_GKI_VFS_EXPORT_ONLY);
437 
438 ssize_t
vfs_listxattr(struct dentry * dentry,char * list,size_t size)439 vfs_listxattr(struct dentry *dentry, char *list, size_t size)
440 {
441 	struct inode *inode = d_inode(dentry);
442 	ssize_t error;
443 
444 	error = security_inode_listxattr(dentry);
445 	if (error)
446 		return error;
447 	if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
448 		error = inode->i_op->listxattr(dentry, list, size);
449 	} else {
450 		error = security_inode_listsecurity(inode, list, size);
451 		if (size && error > size)
452 			error = -ERANGE;
453 	}
454 	return error;
455 }
456 EXPORT_SYMBOL_NS_GPL(vfs_listxattr, ANDROID_GKI_VFS_EXPORT_ONLY);
457 
458 int
__vfs_removexattr(struct user_namespace * mnt_userns,struct dentry * dentry,const char * name)459 __vfs_removexattr(struct user_namespace *mnt_userns, struct dentry *dentry,
460 		  const char *name)
461 {
462 	struct inode *inode = d_inode(dentry);
463 	const struct xattr_handler *handler;
464 
465 	handler = xattr_resolve_name(inode, &name);
466 	if (IS_ERR(handler))
467 		return PTR_ERR(handler);
468 	if (!handler->set)
469 		return -EOPNOTSUPP;
470 	return handler->set(handler, mnt_userns, dentry, inode, name, NULL, 0,
471 			    XATTR_REPLACE);
472 }
473 EXPORT_SYMBOL(__vfs_removexattr);
474 
475 /**
476  * __vfs_removexattr_locked - set an extended attribute while holding the inode
477  * lock
478  *
479  *  @mnt_userns: user namespace of the mount of the target inode
480  *  @dentry: object to perform setxattr on
481  *  @name: name of xattr to remove
482  *  @delegated_inode: on return, will contain an inode pointer that
483  *  a delegation was broken on, NULL if none.
484  */
485 int
__vfs_removexattr_locked(struct user_namespace * mnt_userns,struct dentry * dentry,const char * name,struct inode ** delegated_inode)486 __vfs_removexattr_locked(struct user_namespace *mnt_userns,
487 			 struct dentry *dentry, const char *name,
488 			 struct inode **delegated_inode)
489 {
490 	struct inode *inode = dentry->d_inode;
491 	int error;
492 
493 	error = xattr_permission(mnt_userns, inode, name, MAY_WRITE);
494 	if (error)
495 		return error;
496 
497 	error = security_inode_removexattr(mnt_userns, dentry, name);
498 	if (error)
499 		goto out;
500 
501 	error = try_break_deleg(inode, delegated_inode);
502 	if (error)
503 		goto out;
504 
505 	error = __vfs_removexattr(mnt_userns, dentry, name);
506 
507 	if (!error) {
508 		fsnotify_xattr(dentry);
509 		evm_inode_post_removexattr(dentry, name);
510 	}
511 
512 out:
513 	return error;
514 }
515 EXPORT_SYMBOL_GPL(__vfs_removexattr_locked);
516 
517 int
vfs_removexattr(struct user_namespace * mnt_userns,struct dentry * dentry,const char * name)518 vfs_removexattr(struct user_namespace *mnt_userns, struct dentry *dentry,
519 		const char *name)
520 {
521 	struct inode *inode = dentry->d_inode;
522 	struct inode *delegated_inode = NULL;
523 	int error;
524 
525 retry_deleg:
526 	inode_lock(inode);
527 	error = __vfs_removexattr_locked(mnt_userns, dentry,
528 					 name, &delegated_inode);
529 	inode_unlock(inode);
530 
531 	if (delegated_inode) {
532 		error = break_deleg_wait(&delegated_inode);
533 		if (!error)
534 			goto retry_deleg;
535 	}
536 
537 	return error;
538 }
539 EXPORT_SYMBOL_GPL(vfs_removexattr);
540 
541 /*
542  * Extended attribute SET operations
543  */
544 
setxattr_copy(const char __user * name,struct xattr_ctx * ctx)545 int setxattr_copy(const char __user *name, struct xattr_ctx *ctx)
546 {
547 	int error;
548 
549 	if (ctx->flags & ~(XATTR_CREATE|XATTR_REPLACE))
550 		return -EINVAL;
551 
552 	error = strncpy_from_user(ctx->kname->name, name,
553 				sizeof(ctx->kname->name));
554 	if (error == 0 || error == sizeof(ctx->kname->name))
555 		return  -ERANGE;
556 	if (error < 0)
557 		return error;
558 
559 	error = 0;
560 	if (ctx->size) {
561 		if (ctx->size > XATTR_SIZE_MAX)
562 			return -E2BIG;
563 
564 		ctx->kvalue = vmemdup_user(ctx->cvalue, ctx->size);
565 		if (IS_ERR(ctx->kvalue)) {
566 			error = PTR_ERR(ctx->kvalue);
567 			ctx->kvalue = NULL;
568 		}
569 	}
570 
571 	return error;
572 }
573 
setxattr_convert(struct user_namespace * mnt_userns,struct dentry * d,struct xattr_ctx * ctx)574 static void setxattr_convert(struct user_namespace *mnt_userns,
575 			     struct dentry *d, struct xattr_ctx *ctx)
576 {
577 	if (ctx->size &&
578 		((strcmp(ctx->kname->name, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
579 		(strcmp(ctx->kname->name, XATTR_NAME_POSIX_ACL_DEFAULT) == 0)))
580 		posix_acl_fix_xattr_from_user(mnt_userns, d_inode(d),
581 						ctx->kvalue, ctx->size);
582 }
583 
do_setxattr(struct user_namespace * mnt_userns,struct dentry * dentry,struct xattr_ctx * ctx)584 int do_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
585 		struct xattr_ctx *ctx)
586 {
587 	setxattr_convert(mnt_userns, dentry, ctx);
588 	return vfs_setxattr(mnt_userns, dentry, ctx->kname->name,
589 			ctx->kvalue, ctx->size, ctx->flags);
590 }
591 
592 static long
setxattr(struct user_namespace * mnt_userns,struct dentry * d,const char __user * name,const void __user * value,size_t size,int flags)593 setxattr(struct user_namespace *mnt_userns, struct dentry *d,
594 	const char __user *name, const void __user *value, size_t size,
595 	int flags)
596 {
597 	struct xattr_name kname;
598 	struct xattr_ctx ctx = {
599 		.cvalue   = value,
600 		.kvalue   = NULL,
601 		.size     = size,
602 		.kname    = &kname,
603 		.flags    = flags,
604 	};
605 	int error;
606 
607 	error = setxattr_copy(name, &ctx);
608 	if (error)
609 		return error;
610 
611 	error = do_setxattr(mnt_userns, d, &ctx);
612 
613 	kvfree(ctx.kvalue);
614 	return error;
615 }
616 
path_setxattr(const char __user * pathname,const char __user * name,const void __user * value,size_t size,int flags,unsigned int lookup_flags)617 static int path_setxattr(const char __user *pathname,
618 			 const char __user *name, const void __user *value,
619 			 size_t size, int flags, unsigned int lookup_flags)
620 {
621 	struct path path;
622 	int error;
623 
624 retry:
625 	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
626 	if (error)
627 		return error;
628 	error = mnt_want_write(path.mnt);
629 	if (!error) {
630 		error = setxattr(mnt_user_ns(path.mnt), path.dentry, name,
631 				 value, size, flags);
632 		mnt_drop_write(path.mnt);
633 	}
634 	path_put(&path);
635 	if (retry_estale(error, lookup_flags)) {
636 		lookup_flags |= LOOKUP_REVAL;
637 		goto retry;
638 	}
639 	return error;
640 }
641 
SYSCALL_DEFINE5(setxattr,const char __user *,pathname,const char __user *,name,const void __user *,value,size_t,size,int,flags)642 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
643 		const char __user *, name, const void __user *, value,
644 		size_t, size, int, flags)
645 {
646 	return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
647 }
648 
SYSCALL_DEFINE5(lsetxattr,const char __user *,pathname,const char __user *,name,const void __user *,value,size_t,size,int,flags)649 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
650 		const char __user *, name, const void __user *, value,
651 		size_t, size, int, flags)
652 {
653 	return path_setxattr(pathname, name, value, size, flags, 0);
654 }
655 
SYSCALL_DEFINE5(fsetxattr,int,fd,const char __user *,name,const void __user *,value,size_t,size,int,flags)656 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
657 		const void __user *,value, size_t, size, int, flags)
658 {
659 	struct fd f = fdget(fd);
660 	int error = -EBADF;
661 
662 	if (!f.file)
663 		return error;
664 	audit_file(f.file);
665 	error = mnt_want_write_file(f.file);
666 	if (!error) {
667 		error = setxattr(file_mnt_user_ns(f.file),
668 				 f.file->f_path.dentry, name,
669 				 value, size, flags);
670 		mnt_drop_write_file(f.file);
671 	}
672 	fdput(f);
673 	return error;
674 }
675 
676 /*
677  * Extended attribute GET operations
678  */
679 static ssize_t
getxattr(struct user_namespace * mnt_userns,struct dentry * d,const char __user * name,void __user * value,size_t size)680 getxattr(struct user_namespace *mnt_userns, struct dentry *d,
681 	 const char __user *name, void __user *value, size_t size)
682 {
683 	ssize_t error;
684 	void *kvalue = NULL;
685 	char kname[XATTR_NAME_MAX + 1];
686 
687 	error = strncpy_from_user(kname, name, sizeof(kname));
688 	if (error == 0 || error == sizeof(kname))
689 		error = -ERANGE;
690 	if (error < 0)
691 		return error;
692 
693 	if (size) {
694 		if (size > XATTR_SIZE_MAX)
695 			size = XATTR_SIZE_MAX;
696 		kvalue = kvzalloc(size, GFP_KERNEL);
697 		if (!kvalue)
698 			return -ENOMEM;
699 	}
700 
701 	error = vfs_getxattr(mnt_userns, d, kname, kvalue, size);
702 	if (error > 0) {
703 		if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
704 		    (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
705 			posix_acl_fix_xattr_to_user(mnt_userns, d_inode(d),
706 						    kvalue, error);
707 		if (size && copy_to_user(value, kvalue, error))
708 			error = -EFAULT;
709 	} else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
710 		/* The file system tried to returned a value bigger
711 		   than XATTR_SIZE_MAX bytes. Not possible. */
712 		error = -E2BIG;
713 	}
714 
715 	kvfree(kvalue);
716 
717 	return error;
718 }
719 
path_getxattr(const char __user * pathname,const char __user * name,void __user * value,size_t size,unsigned int lookup_flags)720 static ssize_t path_getxattr(const char __user *pathname,
721 			     const char __user *name, void __user *value,
722 			     size_t size, unsigned int lookup_flags)
723 {
724 	struct path path;
725 	ssize_t error;
726 retry:
727 	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
728 	if (error)
729 		return error;
730 	error = getxattr(mnt_user_ns(path.mnt), path.dentry, name, value, size);
731 	path_put(&path);
732 	if (retry_estale(error, lookup_flags)) {
733 		lookup_flags |= LOOKUP_REVAL;
734 		goto retry;
735 	}
736 	return error;
737 }
738 
SYSCALL_DEFINE4(getxattr,const char __user *,pathname,const char __user *,name,void __user *,value,size_t,size)739 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
740 		const char __user *, name, void __user *, value, size_t, size)
741 {
742 	return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
743 }
744 
SYSCALL_DEFINE4(lgetxattr,const char __user *,pathname,const char __user *,name,void __user *,value,size_t,size)745 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
746 		const char __user *, name, void __user *, value, size_t, size)
747 {
748 	return path_getxattr(pathname, name, value, size, 0);
749 }
750 
SYSCALL_DEFINE4(fgetxattr,int,fd,const char __user *,name,void __user *,value,size_t,size)751 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
752 		void __user *, value, size_t, size)
753 {
754 	struct fd f = fdget(fd);
755 	ssize_t error = -EBADF;
756 
757 	if (!f.file)
758 		return error;
759 	audit_file(f.file);
760 	error = getxattr(file_mnt_user_ns(f.file), f.file->f_path.dentry,
761 			 name, value, size);
762 	fdput(f);
763 	return error;
764 }
765 
766 /*
767  * Extended attribute LIST operations
768  */
769 static ssize_t
listxattr(struct dentry * d,char __user * list,size_t size)770 listxattr(struct dentry *d, char __user *list, size_t size)
771 {
772 	ssize_t error;
773 	char *klist = NULL;
774 
775 	if (size) {
776 		if (size > XATTR_LIST_MAX)
777 			size = XATTR_LIST_MAX;
778 		klist = kvmalloc(size, GFP_KERNEL);
779 		if (!klist)
780 			return -ENOMEM;
781 	}
782 
783 	error = vfs_listxattr(d, klist, size);
784 	if (error > 0) {
785 		if (size && copy_to_user(list, klist, error))
786 			error = -EFAULT;
787 	} else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
788 		/* The file system tried to returned a list bigger
789 		   than XATTR_LIST_MAX bytes. Not possible. */
790 		error = -E2BIG;
791 	}
792 
793 	kvfree(klist);
794 
795 	return error;
796 }
797 
path_listxattr(const char __user * pathname,char __user * list,size_t size,unsigned int lookup_flags)798 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
799 			      size_t size, unsigned int lookup_flags)
800 {
801 	struct path path;
802 	ssize_t error;
803 retry:
804 	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
805 	if (error)
806 		return error;
807 	error = listxattr(path.dentry, list, size);
808 	path_put(&path);
809 	if (retry_estale(error, lookup_flags)) {
810 		lookup_flags |= LOOKUP_REVAL;
811 		goto retry;
812 	}
813 	return error;
814 }
815 
SYSCALL_DEFINE3(listxattr,const char __user *,pathname,char __user *,list,size_t,size)816 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
817 		size_t, size)
818 {
819 	return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
820 }
821 
SYSCALL_DEFINE3(llistxattr,const char __user *,pathname,char __user *,list,size_t,size)822 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
823 		size_t, size)
824 {
825 	return path_listxattr(pathname, list, size, 0);
826 }
827 
SYSCALL_DEFINE3(flistxattr,int,fd,char __user *,list,size_t,size)828 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
829 {
830 	struct fd f = fdget(fd);
831 	ssize_t error = -EBADF;
832 
833 	if (!f.file)
834 		return error;
835 	audit_file(f.file);
836 	error = listxattr(f.file->f_path.dentry, list, size);
837 	fdput(f);
838 	return error;
839 }
840 
841 /*
842  * Extended attribute REMOVE operations
843  */
844 static long
removexattr(struct user_namespace * mnt_userns,struct dentry * d,const char __user * name)845 removexattr(struct user_namespace *mnt_userns, struct dentry *d,
846 	    const char __user *name)
847 {
848 	int error;
849 	char kname[XATTR_NAME_MAX + 1];
850 
851 	error = strncpy_from_user(kname, name, sizeof(kname));
852 	if (error == 0 || error == sizeof(kname))
853 		error = -ERANGE;
854 	if (error < 0)
855 		return error;
856 
857 	return vfs_removexattr(mnt_userns, d, kname);
858 }
859 
path_removexattr(const char __user * pathname,const char __user * name,unsigned int lookup_flags)860 static int path_removexattr(const char __user *pathname,
861 			    const char __user *name, unsigned int lookup_flags)
862 {
863 	struct path path;
864 	int error;
865 retry:
866 	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
867 	if (error)
868 		return error;
869 	error = mnt_want_write(path.mnt);
870 	if (!error) {
871 		error = removexattr(mnt_user_ns(path.mnt), path.dentry, name);
872 		mnt_drop_write(path.mnt);
873 	}
874 	path_put(&path);
875 	if (retry_estale(error, lookup_flags)) {
876 		lookup_flags |= LOOKUP_REVAL;
877 		goto retry;
878 	}
879 	return error;
880 }
881 
SYSCALL_DEFINE2(removexattr,const char __user *,pathname,const char __user *,name)882 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
883 		const char __user *, name)
884 {
885 	return path_removexattr(pathname, name, LOOKUP_FOLLOW);
886 }
887 
SYSCALL_DEFINE2(lremovexattr,const char __user *,pathname,const char __user *,name)888 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
889 		const char __user *, name)
890 {
891 	return path_removexattr(pathname, name, 0);
892 }
893 
SYSCALL_DEFINE2(fremovexattr,int,fd,const char __user *,name)894 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
895 {
896 	struct fd f = fdget(fd);
897 	int error = -EBADF;
898 
899 	if (!f.file)
900 		return error;
901 	audit_file(f.file);
902 	error = mnt_want_write_file(f.file);
903 	if (!error) {
904 		error = removexattr(file_mnt_user_ns(f.file),
905 				    f.file->f_path.dentry, name);
906 		mnt_drop_write_file(f.file);
907 	}
908 	fdput(f);
909 	return error;
910 }
911 
912 /*
913  * Combine the results of the list() operation from every xattr_handler in the
914  * list.
915  */
916 ssize_t
generic_listxattr(struct dentry * dentry,char * buffer,size_t buffer_size)917 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
918 {
919 	const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
920 	unsigned int size = 0;
921 
922 	if (!buffer) {
923 		for_each_xattr_handler(handlers, handler) {
924 			if (!handler->name ||
925 			    (handler->list && !handler->list(dentry)))
926 				continue;
927 			size += strlen(handler->name) + 1;
928 		}
929 	} else {
930 		char *buf = buffer;
931 		size_t len;
932 
933 		for_each_xattr_handler(handlers, handler) {
934 			if (!handler->name ||
935 			    (handler->list && !handler->list(dentry)))
936 				continue;
937 			len = strlen(handler->name);
938 			if (len + 1 > buffer_size)
939 				return -ERANGE;
940 			memcpy(buf, handler->name, len + 1);
941 			buf += len + 1;
942 			buffer_size -= len + 1;
943 		}
944 		size = buf - buffer;
945 	}
946 	return size;
947 }
948 EXPORT_SYMBOL(generic_listxattr);
949 
950 /**
951  * xattr_full_name  -  Compute full attribute name from suffix
952  *
953  * @handler:	handler of the xattr_handler operation
954  * @name:	name passed to the xattr_handler operation
955  *
956  * The get and set xattr handler operations are called with the remainder of
957  * the attribute name after skipping the handler's prefix: for example, "foo"
958  * is passed to the get operation of a handler with prefix "user." to get
959  * attribute "user.foo".  The full name is still "there" in the name though.
960  *
961  * Note: the list xattr handler operation when called from the vfs is passed a
962  * NULL name; some file systems use this operation internally, with varying
963  * semantics.
964  */
xattr_full_name(const struct xattr_handler * handler,const char * name)965 const char *xattr_full_name(const struct xattr_handler *handler,
966 			    const char *name)
967 {
968 	size_t prefix_len = strlen(xattr_prefix(handler));
969 
970 	return name - prefix_len;
971 }
972 EXPORT_SYMBOL(xattr_full_name);
973 
974 /*
975  * Allocate new xattr and copy in the value; but leave the name to callers.
976  */
simple_xattr_alloc(const void * value,size_t size)977 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
978 {
979 	struct simple_xattr *new_xattr;
980 	size_t len;
981 
982 	/* wrap around? */
983 	len = sizeof(*new_xattr) + size;
984 	if (len < sizeof(*new_xattr))
985 		return NULL;
986 
987 	new_xattr = kvmalloc(len, GFP_KERNEL);
988 	if (!new_xattr)
989 		return NULL;
990 
991 	new_xattr->size = size;
992 	memcpy(new_xattr->value, value, size);
993 	return new_xattr;
994 }
995 
996 /*
997  * xattr GET operation for in-memory/pseudo filesystems
998  */
simple_xattr_get(struct simple_xattrs * xattrs,const char * name,void * buffer,size_t size)999 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
1000 		     void *buffer, size_t size)
1001 {
1002 	struct simple_xattr *xattr;
1003 	int ret = -ENODATA;
1004 
1005 	spin_lock(&xattrs->lock);
1006 	list_for_each_entry(xattr, &xattrs->head, list) {
1007 		if (strcmp(name, xattr->name))
1008 			continue;
1009 
1010 		ret = xattr->size;
1011 		if (buffer) {
1012 			if (size < xattr->size)
1013 				ret = -ERANGE;
1014 			else
1015 				memcpy(buffer, xattr->value, xattr->size);
1016 		}
1017 		break;
1018 	}
1019 	spin_unlock(&xattrs->lock);
1020 	return ret;
1021 }
1022 
1023 /**
1024  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
1025  * @xattrs: target simple_xattr list
1026  * @name: name of the extended attribute
1027  * @value: value of the xattr. If %NULL, will remove the attribute.
1028  * @size: size of the new xattr
1029  * @flags: %XATTR_{CREATE|REPLACE}
1030  * @removed_size: returns size of the removed xattr, -1 if none removed
1031  *
1032  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
1033  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
1034  * otherwise, fails with -ENODATA.
1035  *
1036  * Returns 0 on success, -errno on failure.
1037  */
simple_xattr_set(struct simple_xattrs * xattrs,const char * name,const void * value,size_t size,int flags,ssize_t * removed_size)1038 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
1039 		     const void *value, size_t size, int flags,
1040 		     ssize_t *removed_size)
1041 {
1042 	struct simple_xattr *xattr;
1043 	struct simple_xattr *new_xattr = NULL;
1044 	int err = 0;
1045 
1046 	if (removed_size)
1047 		*removed_size = -1;
1048 
1049 	/* value == NULL means remove */
1050 	if (value) {
1051 		new_xattr = simple_xattr_alloc(value, size);
1052 		if (!new_xattr)
1053 			return -ENOMEM;
1054 
1055 		new_xattr->name = kstrdup(name, GFP_KERNEL);
1056 		if (!new_xattr->name) {
1057 			kvfree(new_xattr);
1058 			return -ENOMEM;
1059 		}
1060 	}
1061 
1062 	spin_lock(&xattrs->lock);
1063 	list_for_each_entry(xattr, &xattrs->head, list) {
1064 		if (!strcmp(name, xattr->name)) {
1065 			if (flags & XATTR_CREATE) {
1066 				xattr = new_xattr;
1067 				err = -EEXIST;
1068 			} else if (new_xattr) {
1069 				list_replace(&xattr->list, &new_xattr->list);
1070 				if (removed_size)
1071 					*removed_size = xattr->size;
1072 			} else {
1073 				list_del(&xattr->list);
1074 				if (removed_size)
1075 					*removed_size = xattr->size;
1076 			}
1077 			goto out;
1078 		}
1079 	}
1080 	if (flags & XATTR_REPLACE) {
1081 		xattr = new_xattr;
1082 		err = -ENODATA;
1083 	} else {
1084 		list_add(&new_xattr->list, &xattrs->head);
1085 		xattr = NULL;
1086 	}
1087 out:
1088 	spin_unlock(&xattrs->lock);
1089 	if (xattr) {
1090 		kfree(xattr->name);
1091 		kvfree(xattr);
1092 	}
1093 	return err;
1094 
1095 }
1096 
xattr_is_trusted(const char * name)1097 static bool xattr_is_trusted(const char *name)
1098 {
1099 	return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
1100 }
1101 
xattr_list_one(char ** buffer,ssize_t * remaining_size,const char * name)1102 static int xattr_list_one(char **buffer, ssize_t *remaining_size,
1103 			  const char *name)
1104 {
1105 	size_t len = strlen(name) + 1;
1106 	if (*buffer) {
1107 		if (*remaining_size < len)
1108 			return -ERANGE;
1109 		memcpy(*buffer, name, len);
1110 		*buffer += len;
1111 	}
1112 	*remaining_size -= len;
1113 	return 0;
1114 }
1115 
1116 /*
1117  * xattr LIST operation for in-memory/pseudo filesystems
1118  */
simple_xattr_list(struct inode * inode,struct simple_xattrs * xattrs,char * buffer,size_t size)1119 ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
1120 			  char *buffer, size_t size)
1121 {
1122 	bool trusted = ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN);
1123 	struct simple_xattr *xattr;
1124 	ssize_t remaining_size = size;
1125 	int err = 0;
1126 
1127 #ifdef CONFIG_FS_POSIX_ACL
1128 	if (IS_POSIXACL(inode)) {
1129 		if (inode->i_acl) {
1130 			err = xattr_list_one(&buffer, &remaining_size,
1131 					     XATTR_NAME_POSIX_ACL_ACCESS);
1132 			if (err)
1133 				return err;
1134 		}
1135 		if (inode->i_default_acl) {
1136 			err = xattr_list_one(&buffer, &remaining_size,
1137 					     XATTR_NAME_POSIX_ACL_DEFAULT);
1138 			if (err)
1139 				return err;
1140 		}
1141 	}
1142 #endif
1143 
1144 	spin_lock(&xattrs->lock);
1145 	list_for_each_entry(xattr, &xattrs->head, list) {
1146 		/* skip "trusted." attributes for unprivileged callers */
1147 		if (!trusted && xattr_is_trusted(xattr->name))
1148 			continue;
1149 
1150 		err = xattr_list_one(&buffer, &remaining_size, xattr->name);
1151 		if (err)
1152 			break;
1153 	}
1154 	spin_unlock(&xattrs->lock);
1155 
1156 	return err ? err : size - remaining_size;
1157 }
1158 
1159 /*
1160  * Adds an extended attribute to the list
1161  */
simple_xattr_list_add(struct simple_xattrs * xattrs,struct simple_xattr * new_xattr)1162 void simple_xattr_list_add(struct simple_xattrs *xattrs,
1163 			   struct simple_xattr *new_xattr)
1164 {
1165 	spin_lock(&xattrs->lock);
1166 	list_add(&new_xattr->list, &xattrs->head);
1167 	spin_unlock(&xattrs->lock);
1168 }
1169