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/fs/xattr.c

https://bitbucket.org/emiliolopez/linux
C | 985 lines | 736 code | 114 blank | 135 comment | 162 complexity | d6beb68b1e6423eb1aa74fdd888043c6 MD5 | raw file
  1/*
  2  File: fs/xattr.c
  3
  4  Extended attribute handling.
  5
  6  Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
  7  Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
  8  Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
  9 */
 10#include <linux/fs.h>
 11#include <linux/slab.h>
 12#include <linux/file.h>
 13#include <linux/xattr.h>
 14#include <linux/mount.h>
 15#include <linux/namei.h>
 16#include <linux/security.h>
 17#include <linux/evm.h>
 18#include <linux/syscalls.h>
 19#include <linux/export.h>
 20#include <linux/fsnotify.h>
 21#include <linux/audit.h>
 22#include <linux/vmalloc.h>
 23#include <linux/posix_acl_xattr.h>
 24
 25#include <linux/uaccess.h>
 26
 27static const char *
 28strcmp_prefix(const char *a, const char *a_prefix)
 29{
 30	while (*a_prefix && *a == *a_prefix) {
 31		a++;
 32		a_prefix++;
 33	}
 34	return *a_prefix ? NULL : a;
 35}
 36
 37/*
 38 * In order to implement different sets of xattr operations for each xattr
 39 * prefix, a filesystem should create a null-terminated array of struct
 40 * xattr_handler (one for each prefix) and hang a pointer to it off of the
 41 * s_xattr field of the superblock.
 42 */
 43#define for_each_xattr_handler(handlers, handler)		\
 44	if (handlers)						\
 45		for ((handler) = *(handlers)++;			\
 46			(handler) != NULL;			\
 47			(handler) = *(handlers)++)
 48
 49/*
 50 * Find the xattr_handler with the matching prefix.
 51 */
 52static const struct xattr_handler *
 53xattr_resolve_name(struct inode *inode, const char **name)
 54{
 55	const struct xattr_handler **handlers = inode->i_sb->s_xattr;
 56	const struct xattr_handler *handler;
 57
 58	if (!(inode->i_opflags & IOP_XATTR)) {
 59		if (unlikely(is_bad_inode(inode)))
 60			return ERR_PTR(-EIO);
 61		return ERR_PTR(-EOPNOTSUPP);
 62	}
 63	for_each_xattr_handler(handlers, handler) {
 64		const char *n;
 65
 66		n = strcmp_prefix(*name, xattr_prefix(handler));
 67		if (n) {
 68			if (!handler->prefix ^ !*n) {
 69				if (*n)
 70					continue;
 71				return ERR_PTR(-EINVAL);
 72			}
 73			*name = n;
 74			return handler;
 75		}
 76	}
 77	return ERR_PTR(-EOPNOTSUPP);
 78}
 79
 80/*
 81 * Check permissions for extended attribute access.  This is a bit complicated
 82 * because different namespaces have very different rules.
 83 */
 84static int
 85xattr_permission(struct inode *inode, const char *name, int mask)
 86{
 87	/*
 88	 * We can never set or remove an extended attribute on a read-only
 89	 * filesystem  or on an immutable / append-only inode.
 90	 */
 91	if (mask & MAY_WRITE) {
 92		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 93			return -EPERM;
 94		/*
 95		 * Updating an xattr will likely cause i_uid and i_gid
 96		 * to be writen back improperly if their true value is
 97		 * unknown to the vfs.
 98		 */
 99		if (HAS_UNMAPPED_ID(inode))
100			return -EPERM;
101	}
102
103	/*
104	 * No restriction for security.* and system.* from the VFS.  Decision
105	 * on these is left to the underlying filesystem / security module.
106	 */
107	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
108	    !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
109		return 0;
110
111	/*
112	 * The trusted.* namespace can only be accessed by privileged users.
113	 */
114	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
115		if (!capable(CAP_SYS_ADMIN))
116			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
117		return 0;
118	}
119
120	/*
121	 * In the user.* namespace, only regular files and directories can have
122	 * extended attributes. For sticky directories, only the owner and
123	 * privileged users can write attributes.
124	 */
125	if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
126		if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
127			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
128		if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
129		    (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
130			return -EPERM;
131	}
132
133	return inode_permission(inode, mask);
134}
135
136int
137__vfs_setxattr(struct dentry *dentry, struct inode *inode, const char *name,
138	       const void *value, size_t size, int flags)
139{
140	const struct xattr_handler *handler;
141
142	handler = xattr_resolve_name(inode, &name);
143	if (IS_ERR(handler))
144		return PTR_ERR(handler);
145	if (!handler->set)
146		return -EOPNOTSUPP;
147	if (size == 0)
148		value = "";  /* empty EA, do not remove */
149	return handler->set(handler, dentry, inode, name, value, size, flags);
150}
151EXPORT_SYMBOL(__vfs_setxattr);
152
153/**
154 *  __vfs_setxattr_noperm - perform setxattr operation without performing
155 *  permission checks.
156 *
157 *  @dentry - object to perform setxattr on
158 *  @name - xattr name to set
159 *  @value - value to set @name to
160 *  @size - size of @value
161 *  @flags - flags to pass into filesystem operations
162 *
163 *  returns the result of the internal setxattr or setsecurity operations.
164 *
165 *  This function requires the caller to lock the inode's i_mutex before it
166 *  is executed. It also assumes that the caller will make the appropriate
167 *  permission checks.
168 */
169int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
170		const void *value, size_t size, int flags)
171{
172	struct inode *inode = dentry->d_inode;
173	int error = -EAGAIN;
174	int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
175				   XATTR_SECURITY_PREFIX_LEN);
176
177	if (issec)
178		inode->i_flags &= ~S_NOSEC;
179	if (inode->i_opflags & IOP_XATTR) {
180		error = __vfs_setxattr(dentry, inode, name, value, size, flags);
181		if (!error) {
182			fsnotify_xattr(dentry);
183			security_inode_post_setxattr(dentry, name, value,
184						     size, flags);
185		}
186	} else {
187		if (unlikely(is_bad_inode(inode)))
188			return -EIO;
189	}
190	if (error == -EAGAIN) {
191		error = -EOPNOTSUPP;
192
193		if (issec) {
194			const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
195
196			error = security_inode_setsecurity(inode, suffix, value,
197							   size, flags);
198			if (!error)
199				fsnotify_xattr(dentry);
200		}
201	}
202
203	return error;
204}
205
206
207int
208vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
209		size_t size, int flags)
210{
211	struct inode *inode = dentry->d_inode;
212	int error;
213
214	error = xattr_permission(inode, name, MAY_WRITE);
215	if (error)
216		return error;
217
218	inode_lock(inode);
219	error = security_inode_setxattr(dentry, name, value, size, flags);
220	if (error)
221		goto out;
222
223	error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
224
225out:
226	inode_unlock(inode);
227	return error;
228}
229EXPORT_SYMBOL_GPL(vfs_setxattr);
230
231ssize_t
232xattr_getsecurity(struct inode *inode, const char *name, void *value,
233			size_t size)
234{
235	void *buffer = NULL;
236	ssize_t len;
237
238	if (!value || !size) {
239		len = security_inode_getsecurity(inode, name, &buffer, false);
240		goto out_noalloc;
241	}
242
243	len = security_inode_getsecurity(inode, name, &buffer, true);
244	if (len < 0)
245		return len;
246	if (size < len) {
247		len = -ERANGE;
248		goto out;
249	}
250	memcpy(value, buffer, len);
251out:
252	security_release_secctx(buffer, len);
253out_noalloc:
254	return len;
255}
256EXPORT_SYMBOL_GPL(xattr_getsecurity);
257
258/*
259 * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
260 *
261 * Allocate memory, if not already allocated, or re-allocate correct size,
262 * before retrieving the extended attribute.
263 *
264 * Returns the result of alloc, if failed, or the getxattr operation.
265 */
266ssize_t
267vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
268		   size_t xattr_size, gfp_t flags)
269{
270	const struct xattr_handler *handler;
271	struct inode *inode = dentry->d_inode;
272	char *value = *xattr_value;
273	int error;
274
275	error = xattr_permission(inode, name, MAY_READ);
276	if (error)
277		return error;
278
279	handler = xattr_resolve_name(inode, &name);
280	if (IS_ERR(handler))
281		return PTR_ERR(handler);
282	if (!handler->get)
283		return -EOPNOTSUPP;
284	error = handler->get(handler, dentry, inode, name, NULL, 0);
285	if (error < 0)
286		return error;
287
288	if (!value || (error > xattr_size)) {
289		value = krealloc(*xattr_value, error + 1, flags);
290		if (!value)
291			return -ENOMEM;
292		memset(value, 0, error + 1);
293	}
294
295	error = handler->get(handler, dentry, inode, name, value, error);
296	*xattr_value = value;
297	return error;
298}
299
300ssize_t
301__vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
302	       void *value, size_t size)
303{
304	const struct xattr_handler *handler;
305
306	handler = xattr_resolve_name(inode, &name);
307	if (IS_ERR(handler))
308		return PTR_ERR(handler);
309	if (!handler->get)
310		return -EOPNOTSUPP;
311	return handler->get(handler, dentry, inode, name, value, size);
312}
313EXPORT_SYMBOL(__vfs_getxattr);
314
315ssize_t
316vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
317{
318	struct inode *inode = dentry->d_inode;
319	int error;
320
321	error = xattr_permission(inode, name, MAY_READ);
322	if (error)
323		return error;
324
325	error = security_inode_getxattr(dentry, name);
326	if (error)
327		return error;
328
329	if (!strncmp(name, XATTR_SECURITY_PREFIX,
330				XATTR_SECURITY_PREFIX_LEN)) {
331		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
332		int ret = xattr_getsecurity(inode, suffix, value, size);
333		/*
334		 * Only overwrite the return value if a security module
335		 * is actually active.
336		 */
337		if (ret == -EOPNOTSUPP)
338			goto nolsm;
339		return ret;
340	}
341nolsm:
342	return __vfs_getxattr(dentry, inode, name, value, size);
343}
344EXPORT_SYMBOL_GPL(vfs_getxattr);
345
346ssize_t
347vfs_listxattr(struct dentry *dentry, char *list, size_t size)
348{
349	struct inode *inode = d_inode(dentry);
350	ssize_t error;
351
352	error = security_inode_listxattr(dentry);
353	if (error)
354		return error;
355	if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
356		error = -EOPNOTSUPP;
357		error = inode->i_op->listxattr(dentry, list, size);
358	} else {
359		error = security_inode_listsecurity(inode, list, size);
360		if (size && error > size)
361			error = -ERANGE;
362	}
363	return error;
364}
365EXPORT_SYMBOL_GPL(vfs_listxattr);
366
367int
368__vfs_removexattr(struct dentry *dentry, const char *name)
369{
370	struct inode *inode = d_inode(dentry);
371	const struct xattr_handler *handler;
372
373	handler = xattr_resolve_name(inode, &name);
374	if (IS_ERR(handler))
375		return PTR_ERR(handler);
376	if (!handler->set)
377		return -EOPNOTSUPP;
378	return handler->set(handler, dentry, inode, name, NULL, 0, XATTR_REPLACE);
379}
380EXPORT_SYMBOL(__vfs_removexattr);
381
382int
383vfs_removexattr(struct dentry *dentry, const char *name)
384{
385	struct inode *inode = dentry->d_inode;
386	int error;
387
388	error = xattr_permission(inode, name, MAY_WRITE);
389	if (error)
390		return error;
391
392	inode_lock(inode);
393	error = security_inode_removexattr(dentry, name);
394	if (error)
395		goto out;
396
397	error = __vfs_removexattr(dentry, name);
398
399	if (!error) {
400		fsnotify_xattr(dentry);
401		evm_inode_post_removexattr(dentry, name);
402	}
403
404out:
405	inode_unlock(inode);
406	return error;
407}
408EXPORT_SYMBOL_GPL(vfs_removexattr);
409
410
411/*
412 * Extended attribute SET operations
413 */
414static long
415setxattr(struct dentry *d, const char __user *name, const void __user *value,
416	 size_t size, int flags)
417{
418	int error;
419	void *kvalue = NULL;
420	char kname[XATTR_NAME_MAX + 1];
421
422	if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
423		return -EINVAL;
424
425	error = strncpy_from_user(kname, name, sizeof(kname));
426	if (error == 0 || error == sizeof(kname))
427		error = -ERANGE;
428	if (error < 0)
429		return error;
430
431	if (size) {
432		if (size > XATTR_SIZE_MAX)
433			return -E2BIG;
434		kvalue = kvmalloc(size, GFP_KERNEL);
435		if (!kvalue)
436			return -ENOMEM;
437		if (copy_from_user(kvalue, value, size)) {
438			error = -EFAULT;
439			goto out;
440		}
441		if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
442		    (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
443			posix_acl_fix_xattr_from_user(kvalue, size);
444	}
445
446	error = vfs_setxattr(d, kname, kvalue, size, flags);
447out:
448	kvfree(kvalue);
449
450	return error;
451}
452
453static int path_setxattr(const char __user *pathname,
454			 const char __user *name, const void __user *value,
455			 size_t size, int flags, unsigned int lookup_flags)
456{
457	struct path path;
458	int error;
459retry:
460	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
461	if (error)
462		return error;
463	error = mnt_want_write(path.mnt);
464	if (!error) {
465		error = setxattr(path.dentry, name, value, size, flags);
466		mnt_drop_write(path.mnt);
467	}
468	path_put(&path);
469	if (retry_estale(error, lookup_flags)) {
470		lookup_flags |= LOOKUP_REVAL;
471		goto retry;
472	}
473	return error;
474}
475
476SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
477		const char __user *, name, const void __user *, value,
478		size_t, size, int, flags)
479{
480	return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
481}
482
483SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
484		const char __user *, name, const void __user *, value,
485		size_t, size, int, flags)
486{
487	return path_setxattr(pathname, name, value, size, flags, 0);
488}
489
490SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
491		const void __user *,value, size_t, size, int, flags)
492{
493	struct fd f = fdget(fd);
494	int error = -EBADF;
495
496	if (!f.file)
497		return error;
498	audit_file(f.file);
499	error = mnt_want_write_file(f.file);
500	if (!error) {
501		error = setxattr(f.file->f_path.dentry, name, value, size, flags);
502		mnt_drop_write_file(f.file);
503	}
504	fdput(f);
505	return error;
506}
507
508/*
509 * Extended attribute GET operations
510 */
511static ssize_t
512getxattr(struct dentry *d, const char __user *name, void __user *value,
513	 size_t size)
514{
515	ssize_t error;
516	void *kvalue = NULL;
517	char kname[XATTR_NAME_MAX + 1];
518
519	error = strncpy_from_user(kname, name, sizeof(kname));
520	if (error == 0 || error == sizeof(kname))
521		error = -ERANGE;
522	if (error < 0)
523		return error;
524
525	if (size) {
526		if (size > XATTR_SIZE_MAX)
527			size = XATTR_SIZE_MAX;
528		kvalue = kvzalloc(size, GFP_KERNEL);
529		if (!kvalue)
530			return -ENOMEM;
531	}
532
533	error = vfs_getxattr(d, kname, kvalue, size);
534	if (error > 0) {
535		if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
536		    (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
537			posix_acl_fix_xattr_to_user(kvalue, size);
538		if (size && copy_to_user(value, kvalue, error))
539			error = -EFAULT;
540	} else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
541		/* The file system tried to returned a value bigger
542		   than XATTR_SIZE_MAX bytes. Not possible. */
543		error = -E2BIG;
544	}
545
546	kvfree(kvalue);
547
548	return error;
549}
550
551static ssize_t path_getxattr(const char __user *pathname,
552			     const char __user *name, void __user *value,
553			     size_t size, unsigned int lookup_flags)
554{
555	struct path path;
556	ssize_t error;
557retry:
558	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
559	if (error)
560		return error;
561	error = getxattr(path.dentry, name, value, size);
562	path_put(&path);
563	if (retry_estale(error, lookup_flags)) {
564		lookup_flags |= LOOKUP_REVAL;
565		goto retry;
566	}
567	return error;
568}
569
570SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
571		const char __user *, name, void __user *, value, size_t, size)
572{
573	return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
574}
575
576SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
577		const char __user *, name, void __user *, value, size_t, size)
578{
579	return path_getxattr(pathname, name, value, size, 0);
580}
581
582SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
583		void __user *, value, size_t, size)
584{
585	struct fd f = fdget(fd);
586	ssize_t error = -EBADF;
587
588	if (!f.file)
589		return error;
590	audit_file(f.file);
591	error = getxattr(f.file->f_path.dentry, name, value, size);
592	fdput(f);
593	return error;
594}
595
596/*
597 * Extended attribute LIST operations
598 */
599static ssize_t
600listxattr(struct dentry *d, char __user *list, size_t size)
601{
602	ssize_t error;
603	char *klist = NULL;
604
605	if (size) {
606		if (size > XATTR_LIST_MAX)
607			size = XATTR_LIST_MAX;
608		klist = kvmalloc(size, GFP_KERNEL);
609		if (!klist)
610			return -ENOMEM;
611	}
612
613	error = vfs_listxattr(d, klist, size);
614	if (error > 0) {
615		if (size && copy_to_user(list, klist, error))
616			error = -EFAULT;
617	} else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
618		/* The file system tried to returned a list bigger
619		   than XATTR_LIST_MAX bytes. Not possible. */
620		error = -E2BIG;
621	}
622
623	kvfree(klist);
624
625	return error;
626}
627
628static ssize_t path_listxattr(const char __user *pathname, char __user *list,
629			      size_t size, unsigned int lookup_flags)
630{
631	struct path path;
632	ssize_t error;
633retry:
634	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
635	if (error)
636		return error;
637	error = listxattr(path.dentry, list, size);
638	path_put(&path);
639	if (retry_estale(error, lookup_flags)) {
640		lookup_flags |= LOOKUP_REVAL;
641		goto retry;
642	}
643	return error;
644}
645
646SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
647		size_t, size)
648{
649	return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
650}
651
652SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
653		size_t, size)
654{
655	return path_listxattr(pathname, list, size, 0);
656}
657
658SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
659{
660	struct fd f = fdget(fd);
661	ssize_t error = -EBADF;
662
663	if (!f.file)
664		return error;
665	audit_file(f.file);
666	error = listxattr(f.file->f_path.dentry, list, size);
667	fdput(f);
668	return error;
669}
670
671/*
672 * Extended attribute REMOVE operations
673 */
674static long
675removexattr(struct dentry *d, const char __user *name)
676{
677	int error;
678	char kname[XATTR_NAME_MAX + 1];
679
680	error = strncpy_from_user(kname, name, sizeof(kname));
681	if (error == 0 || error == sizeof(kname))
682		error = -ERANGE;
683	if (error < 0)
684		return error;
685
686	return vfs_removexattr(d, kname);
687}
688
689static int path_removexattr(const char __user *pathname,
690			    const char __user *name, unsigned int lookup_flags)
691{
692	struct path path;
693	int error;
694retry:
695	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
696	if (error)
697		return error;
698	error = mnt_want_write(path.mnt);
699	if (!error) {
700		error = removexattr(path.dentry, name);
701		mnt_drop_write(path.mnt);
702	}
703	path_put(&path);
704	if (retry_estale(error, lookup_flags)) {
705		lookup_flags |= LOOKUP_REVAL;
706		goto retry;
707	}
708	return error;
709}
710
711SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
712		const char __user *, name)
713{
714	return path_removexattr(pathname, name, LOOKUP_FOLLOW);
715}
716
717SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
718		const char __user *, name)
719{
720	return path_removexattr(pathname, name, 0);
721}
722
723SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
724{
725	struct fd f = fdget(fd);
726	int error = -EBADF;
727
728	if (!f.file)
729		return error;
730	audit_file(f.file);
731	error = mnt_want_write_file(f.file);
732	if (!error) {
733		error = removexattr(f.file->f_path.dentry, name);
734		mnt_drop_write_file(f.file);
735	}
736	fdput(f);
737	return error;
738}
739
740/*
741 * Combine the results of the list() operation from every xattr_handler in the
742 * list.
743 */
744ssize_t
745generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
746{
747	const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
748	unsigned int size = 0;
749
750	if (!buffer) {
751		for_each_xattr_handler(handlers, handler) {
752			if (!handler->name ||
753			    (handler->list && !handler->list(dentry)))
754				continue;
755			size += strlen(handler->name) + 1;
756		}
757	} else {
758		char *buf = buffer;
759		size_t len;
760
761		for_each_xattr_handler(handlers, handler) {
762			if (!handler->name ||
763			    (handler->list && !handler->list(dentry)))
764				continue;
765			len = strlen(handler->name);
766			if (len + 1 > buffer_size)
767				return -ERANGE;
768			memcpy(buf, handler->name, len + 1);
769			buf += len + 1;
770			buffer_size -= len + 1;
771		}
772		size = buf - buffer;
773	}
774	return size;
775}
776EXPORT_SYMBOL(generic_listxattr);
777
778/**
779 * xattr_full_name  -  Compute full attribute name from suffix
780 *
781 * @handler:	handler of the xattr_handler operation
782 * @name:	name passed to the xattr_handler operation
783 *
784 * The get and set xattr handler operations are called with the remainder of
785 * the attribute name after skipping the handler's prefix: for example, "foo"
786 * is passed to the get operation of a handler with prefix "user." to get
787 * attribute "user.foo".  The full name is still "there" in the name though.
788 *
789 * Note: the list xattr handler operation when called from the vfs is passed a
790 * NULL name; some file systems use this operation internally, with varying
791 * semantics.
792 */
793const char *xattr_full_name(const struct xattr_handler *handler,
794			    const char *name)
795{
796	size_t prefix_len = strlen(xattr_prefix(handler));
797
798	return name - prefix_len;
799}
800EXPORT_SYMBOL(xattr_full_name);
801
802/*
803 * Allocate new xattr and copy in the value; but leave the name to callers.
804 */
805struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
806{
807	struct simple_xattr *new_xattr;
808	size_t len;
809
810	/* wrap around? */
811	len = sizeof(*new_xattr) + size;
812	if (len < sizeof(*new_xattr))
813		return NULL;
814
815	new_xattr = kmalloc(len, GFP_KERNEL);
816	if (!new_xattr)
817		return NULL;
818
819	new_xattr->size = size;
820	memcpy(new_xattr->value, value, size);
821	return new_xattr;
822}
823
824/*
825 * xattr GET operation for in-memory/pseudo filesystems
826 */
827int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
828		     void *buffer, size_t size)
829{
830	struct simple_xattr *xattr;
831	int ret = -ENODATA;
832
833	spin_lock(&xattrs->lock);
834	list_for_each_entry(xattr, &xattrs->head, list) {
835		if (strcmp(name, xattr->name))
836			continue;
837
838		ret = xattr->size;
839		if (buffer) {
840			if (size < xattr->size)
841				ret = -ERANGE;
842			else
843				memcpy(buffer, xattr->value, xattr->size);
844		}
845		break;
846	}
847	spin_unlock(&xattrs->lock);
848	return ret;
849}
850
851/**
852 * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
853 * @xattrs: target simple_xattr list
854 * @name: name of the extended attribute
855 * @value: value of the xattr. If %NULL, will remove the attribute.
856 * @size: size of the new xattr
857 * @flags: %XATTR_{CREATE|REPLACE}
858 *
859 * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
860 * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
861 * otherwise, fails with -ENODATA.
862 *
863 * Returns 0 on success, -errno on failure.
864 */
865int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
866		     const void *value, size_t size, int flags)
867{
868	struct simple_xattr *xattr;
869	struct simple_xattr *new_xattr = NULL;
870	int err = 0;
871
872	/* value == NULL means remove */
873	if (value) {
874		new_xattr = simple_xattr_alloc(value, size);
875		if (!new_xattr)
876			return -ENOMEM;
877
878		new_xattr->name = kstrdup(name, GFP_KERNEL);
879		if (!new_xattr->name) {
880			kfree(new_xattr);
881			return -ENOMEM;
882		}
883	}
884
885	spin_lock(&xattrs->lock);
886	list_for_each_entry(xattr, &xattrs->head, list) {
887		if (!strcmp(name, xattr->name)) {
888			if (flags & XATTR_CREATE) {
889				xattr = new_xattr;
890				err = -EEXIST;
891			} else if (new_xattr) {
892				list_replace(&xattr->list, &new_xattr->list);
893			} else {
894				list_del(&xattr->list);
895			}
896			goto out;
897		}
898	}
899	if (flags & XATTR_REPLACE) {
900		xattr = new_xattr;
901		err = -ENODATA;
902	} else {
903		list_add(&new_xattr->list, &xattrs->head);
904		xattr = NULL;
905	}
906out:
907	spin_unlock(&xattrs->lock);
908	if (xattr) {
909		kfree(xattr->name);
910		kfree(xattr);
911	}
912	return err;
913
914}
915
916static bool xattr_is_trusted(const char *name)
917{
918	return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
919}
920
921static int xattr_list_one(char **buffer, ssize_t *remaining_size,
922			  const char *name)
923{
924	size_t len = strlen(name) + 1;
925	if (*buffer) {
926		if (*remaining_size < len)
927			return -ERANGE;
928		memcpy(*buffer, name, len);
929		*buffer += len;
930	}
931	*remaining_size -= len;
932	return 0;
933}
934
935/*
936 * xattr LIST operation for in-memory/pseudo filesystems
937 */
938ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
939			  char *buffer, size_t size)
940{
941	bool trusted = capable(CAP_SYS_ADMIN);
942	struct simple_xattr *xattr;
943	ssize_t remaining_size = size;
944	int err = 0;
945
946#ifdef CONFIG_FS_POSIX_ACL
947	if (inode->i_acl) {
948		err = xattr_list_one(&buffer, &remaining_size,
949				     XATTR_NAME_POSIX_ACL_ACCESS);
950		if (err)
951			return err;
952	}
953	if (inode->i_default_acl) {
954		err = xattr_list_one(&buffer, &remaining_size,
955				     XATTR_NAME_POSIX_ACL_DEFAULT);
956		if (err)
957			return err;
958	}
959#endif
960
961	spin_lock(&xattrs->lock);
962	list_for_each_entry(xattr, &xattrs->head, list) {
963		/* skip "trusted." attributes for unprivileged callers */
964		if (!trusted && xattr_is_trusted(xattr->name))
965			continue;
966
967		err = xattr_list_one(&buffer, &remaining_size, xattr->name);
968		if (err)
969			break;
970	}
971	spin_unlock(&xattrs->lock);
972
973	return err ? err : size - remaining_size;
974}
975
976/*
977 * Adds an extended attribute to the list
978 */
979void simple_xattr_list_add(struct simple_xattrs *xattrs,
980			   struct simple_xattr *new_xattr)
981{
982	spin_lock(&xattrs->lock);
983	list_add(&new_xattr->list, &xattrs->head);
984	spin_unlock(&xattrs->lock);
985}