4 Extended attribute handling.
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>
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>
25 #include <asm/uaccess.h>
28 * Check permissions for extended attribute access. This is a bit complicated
29 * because different namespaces have very different rules.
32 xattr_permission(struct inode
*inode
, const char *name
, int mask
)
35 * We can never set or remove an extended attribute on a read-only
36 * filesystem or on an immutable / append-only inode.
38 if (mask
& MAY_WRITE
) {
39 if (IS_IMMUTABLE(inode
) || IS_APPEND(inode
))
44 * No restriction for security.* and system.* from the VFS. Decision
45 * on these is left to the underlying filesystem / security module.
47 if (!strncmp(name
, XATTR_SECURITY_PREFIX
, XATTR_SECURITY_PREFIX_LEN
) ||
48 !strncmp(name
, XATTR_SYSTEM_PREFIX
, XATTR_SYSTEM_PREFIX_LEN
))
52 * The trusted.* namespace can only be accessed by privileged users.
54 if (!strncmp(name
, XATTR_TRUSTED_PREFIX
, XATTR_TRUSTED_PREFIX_LEN
)) {
55 if (!capable(CAP_SYS_ADMIN
))
56 return (mask
& MAY_WRITE
) ? -EPERM
: -ENODATA
;
61 * In the user.* namespace, only regular files and directories can have
62 * extended attributes. For sticky directories, only the owner and
63 * privileged users can write attributes.
65 if (!strncmp(name
, XATTR_USER_PREFIX
, XATTR_USER_PREFIX_LEN
)) {
66 if (!S_ISREG(inode
->i_mode
) && !S_ISDIR(inode
->i_mode
))
67 return (mask
& MAY_WRITE
) ? -EPERM
: -ENODATA
;
68 if (S_ISDIR(inode
->i_mode
) && (inode
->i_mode
& S_ISVTX
) &&
69 (mask
& MAY_WRITE
) && !inode_owner_or_capable(inode
))
73 return inode_permission(inode
, mask
);
77 * __vfs_setxattr_noperm - perform setxattr operation without performing
80 * @dentry - object to perform setxattr on
81 * @name - xattr name to set
82 * @value - value to set @name to
83 * @size - size of @value
84 * @flags - flags to pass into filesystem operations
86 * returns the result of the internal setxattr or setsecurity operations.
88 * This function requires the caller to lock the inode's i_mutex before it
89 * is executed. It also assumes that the caller will make the appropriate
92 int __vfs_setxattr_noperm(struct dentry
*dentry
, const char *name
,
93 const void *value
, size_t size
, int flags
)
95 struct inode
*inode
= dentry
->d_inode
;
96 int error
= -EOPNOTSUPP
;
97 int issec
= !strncmp(name
, XATTR_SECURITY_PREFIX
,
98 XATTR_SECURITY_PREFIX_LEN
);
101 inode
->i_flags
&= ~S_NOSEC
;
102 if (inode
->i_op
->setxattr
) {
103 error
= inode
->i_op
->setxattr(dentry
, name
, value
, size
, flags
);
105 fsnotify_xattr(dentry
);
106 security_inode_post_setxattr(dentry
, name
, value
,
110 const char *suffix
= name
+ XATTR_SECURITY_PREFIX_LEN
;
111 error
= security_inode_setsecurity(inode
, suffix
, value
,
114 fsnotify_xattr(dentry
);
122 vfs_setxattr(struct dentry
*dentry
, const char *name
, const void *value
,
123 size_t size
, int flags
)
125 struct inode
*inode
= dentry
->d_inode
;
128 error
= xattr_permission(inode
, name
, MAY_WRITE
);
132 mutex_lock(&inode
->i_mutex
);
133 error
= security_inode_setxattr(dentry
, name
, value
, size
, flags
);
137 error
= __vfs_setxattr_noperm(dentry
, name
, value
, size
, flags
);
140 mutex_unlock(&inode
->i_mutex
);
143 EXPORT_SYMBOL_GPL(vfs_setxattr
);
146 xattr_getsecurity(struct inode
*inode
, const char *name
, void *value
,
152 if (!value
|| !size
) {
153 len
= security_inode_getsecurity(inode
, name
, &buffer
, false);
157 len
= security_inode_getsecurity(inode
, name
, &buffer
, true);
164 memcpy(value
, buffer
, len
);
166 security_release_secctx(buffer
, len
);
170 EXPORT_SYMBOL_GPL(xattr_getsecurity
);
173 * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
175 * Allocate memory, if not already allocated, or re-allocate correct size,
176 * before retrieving the extended attribute.
178 * Returns the result of alloc, if failed, or the getxattr operation.
181 vfs_getxattr_alloc(struct dentry
*dentry
, const char *name
, char **xattr_value
,
182 size_t xattr_size
, gfp_t flags
)
184 struct inode
*inode
= dentry
->d_inode
;
185 char *value
= *xattr_value
;
188 error
= xattr_permission(inode
, name
, MAY_READ
);
192 if (!inode
->i_op
->getxattr
)
195 error
= inode
->i_op
->getxattr(dentry
, name
, NULL
, 0);
199 if (!value
|| (error
> xattr_size
)) {
200 value
= krealloc(*xattr_value
, error
+ 1, flags
);
203 memset(value
, 0, error
+ 1);
206 error
= inode
->i_op
->getxattr(dentry
, name
, value
, error
);
207 *xattr_value
= value
;
211 /* Compare an extended attribute value with the given value */
212 int vfs_xattr_cmp(struct dentry
*dentry
, const char *xattr_name
,
213 const char *value
, size_t size
, gfp_t flags
)
215 char *xattr_value
= NULL
;
218 rc
= vfs_getxattr_alloc(dentry
, xattr_name
, &xattr_value
, 0, flags
);
222 if ((rc
!= size
) || (memcmp(xattr_value
, value
, rc
) != 0))
231 vfs_getxattr(struct dentry
*dentry
, const char *name
, void *value
, size_t size
)
233 struct inode
*inode
= dentry
->d_inode
;
236 error
= xattr_permission(inode
, name
, MAY_READ
);
240 error
= security_inode_getxattr(dentry
, name
);
244 if (!strncmp(name
, XATTR_SECURITY_PREFIX
,
245 XATTR_SECURITY_PREFIX_LEN
)) {
246 const char *suffix
= name
+ XATTR_SECURITY_PREFIX_LEN
;
247 int ret
= xattr_getsecurity(inode
, suffix
, value
, size
);
249 * Only overwrite the return value if a security module
250 * is actually active.
252 if (ret
== -EOPNOTSUPP
)
257 if (inode
->i_op
->getxattr
)
258 error
= inode
->i_op
->getxattr(dentry
, name
, value
, size
);
264 EXPORT_SYMBOL_GPL(vfs_getxattr
);
267 vfs_listxattr(struct dentry
*d
, char *list
, size_t size
)
271 error
= security_inode_listxattr(d
);
275 if (d
->d_inode
->i_op
->listxattr
) {
276 error
= d
->d_inode
->i_op
->listxattr(d
, list
, size
);
278 error
= security_inode_listsecurity(d
->d_inode
, list
, size
);
279 if (size
&& error
> size
)
284 EXPORT_SYMBOL_GPL(vfs_listxattr
);
287 vfs_removexattr(struct dentry
*dentry
, const char *name
)
289 struct inode
*inode
= dentry
->d_inode
;
292 if (!inode
->i_op
->removexattr
)
295 error
= xattr_permission(inode
, name
, MAY_WRITE
);
299 mutex_lock(&inode
->i_mutex
);
300 error
= security_inode_removexattr(dentry
, name
);
302 mutex_unlock(&inode
->i_mutex
);
306 error
= inode
->i_op
->removexattr(dentry
, name
);
307 mutex_unlock(&inode
->i_mutex
);
310 fsnotify_xattr(dentry
);
311 evm_inode_post_removexattr(dentry
, name
);
315 EXPORT_SYMBOL_GPL(vfs_removexattr
);
319 * Extended attribute SET operations
322 setxattr(struct dentry
*d
, const char __user
*name
, const void __user
*value
,
323 size_t size
, int flags
)
327 void *vvalue
= NULL
; /* If non-NULL, we used vmalloc() */
328 char kname
[XATTR_NAME_MAX
+ 1];
330 if (flags
& ~(XATTR_CREATE
|XATTR_REPLACE
))
333 error
= strncpy_from_user(kname
, name
, sizeof(kname
));
334 if (error
== 0 || error
== sizeof(kname
))
340 if (size
> XATTR_SIZE_MAX
)
342 kvalue
= kmalloc(size
, GFP_KERNEL
| __GFP_NOWARN
);
344 vvalue
= vmalloc(size
);
349 if (copy_from_user(kvalue
, value
, size
)) {
353 if ((strcmp(kname
, XATTR_NAME_POSIX_ACL_ACCESS
) == 0) ||
354 (strcmp(kname
, XATTR_NAME_POSIX_ACL_DEFAULT
) == 0))
355 posix_acl_fix_xattr_from_user(kvalue
, size
);
358 error
= vfs_setxattr(d
, kname
, kvalue
, size
, flags
);
367 SYSCALL_DEFINE5(setxattr
, const char __user
*, pathname
,
368 const char __user
*, name
, const void __user
*, value
,
369 size_t, size
, int, flags
)
374 error
= user_path(pathname
, &path
);
377 error
= mnt_want_write(path
.mnt
);
379 error
= setxattr(path
.dentry
, name
, value
, size
, flags
);
380 mnt_drop_write(path
.mnt
);
386 SYSCALL_DEFINE5(lsetxattr
, const char __user
*, pathname
,
387 const char __user
*, name
, const void __user
*, value
,
388 size_t, size
, int, flags
)
393 error
= user_lpath(pathname
, &path
);
396 error
= mnt_want_write(path
.mnt
);
398 error
= setxattr(path
.dentry
, name
, value
, size
, flags
);
399 mnt_drop_write(path
.mnt
);
405 SYSCALL_DEFINE5(fsetxattr
, int, fd
, const char __user
*, name
,
406 const void __user
*,value
, size_t, size
, int, flags
)
408 struct fd f
= fdget(fd
);
409 struct dentry
*dentry
;
414 dentry
= f
.file
->f_path
.dentry
;
415 audit_inode(NULL
, dentry
, 0);
416 error
= mnt_want_write_file(f
.file
);
418 error
= setxattr(dentry
, name
, value
, size
, flags
);
419 mnt_drop_write_file(f
.file
);
426 * Extended attribute GET operations
429 getxattr(struct dentry
*d
, const char __user
*name
, void __user
*value
,
435 char kname
[XATTR_NAME_MAX
+ 1];
437 error
= strncpy_from_user(kname
, name
, sizeof(kname
));
438 if (error
== 0 || error
== sizeof(kname
))
444 if (size
> XATTR_SIZE_MAX
)
445 size
= XATTR_SIZE_MAX
;
446 kvalue
= kzalloc(size
, GFP_KERNEL
| __GFP_NOWARN
);
448 vvalue
= vmalloc(size
);
455 error
= vfs_getxattr(d
, kname
, kvalue
, size
);
457 if ((strcmp(kname
, XATTR_NAME_POSIX_ACL_ACCESS
) == 0) ||
458 (strcmp(kname
, XATTR_NAME_POSIX_ACL_DEFAULT
) == 0))
459 posix_acl_fix_xattr_to_user(kvalue
, size
);
460 if (size
&& copy_to_user(value
, kvalue
, error
))
462 } else if (error
== -ERANGE
&& size
>= XATTR_SIZE_MAX
) {
463 /* The file system tried to returned a value bigger
464 than XATTR_SIZE_MAX bytes. Not possible. */
474 SYSCALL_DEFINE4(getxattr
, const char __user
*, pathname
,
475 const char __user
*, name
, void __user
*, value
, size_t, size
)
480 error
= user_path(pathname
, &path
);
483 error
= getxattr(path
.dentry
, name
, value
, size
);
488 SYSCALL_DEFINE4(lgetxattr
, const char __user
*, pathname
,
489 const char __user
*, name
, void __user
*, value
, size_t, size
)
494 error
= user_lpath(pathname
, &path
);
497 error
= getxattr(path
.dentry
, name
, value
, size
);
502 SYSCALL_DEFINE4(fgetxattr
, int, fd
, const char __user
*, name
,
503 void __user
*, value
, size_t, size
)
505 struct fd f
= fdget(fd
);
506 ssize_t error
= -EBADF
;
510 audit_inode(NULL
, f
.file
->f_path
.dentry
, 0);
511 error
= getxattr(f
.file
->f_path
.dentry
, name
, value
, size
);
517 * Extended attribute LIST operations
520 listxattr(struct dentry
*d
, char __user
*list
, size_t size
)
524 char *vlist
= NULL
; /* If non-NULL, we used vmalloc() */
527 if (size
> XATTR_LIST_MAX
)
528 size
= XATTR_LIST_MAX
;
529 klist
= kmalloc(size
, __GFP_NOWARN
| GFP_KERNEL
);
531 vlist
= vmalloc(size
);
538 error
= vfs_listxattr(d
, klist
, size
);
540 if (size
&& copy_to_user(list
, klist
, error
))
542 } else if (error
== -ERANGE
&& size
>= XATTR_LIST_MAX
) {
543 /* The file system tried to returned a list bigger
544 than XATTR_LIST_MAX bytes. Not possible. */
554 SYSCALL_DEFINE3(listxattr
, const char __user
*, pathname
, char __user
*, list
,
560 error
= user_path(pathname
, &path
);
563 error
= listxattr(path
.dentry
, list
, size
);
568 SYSCALL_DEFINE3(llistxattr
, const char __user
*, pathname
, char __user
*, list
,
574 error
= user_lpath(pathname
, &path
);
577 error
= listxattr(path
.dentry
, list
, size
);
582 SYSCALL_DEFINE3(flistxattr
, int, fd
, char __user
*, list
, size_t, size
)
584 struct fd f
= fdget(fd
);
585 ssize_t error
= -EBADF
;
589 audit_inode(NULL
, f
.file
->f_path
.dentry
, 0);
590 error
= listxattr(f
.file
->f_path
.dentry
, list
, size
);
596 * Extended attribute REMOVE operations
599 removexattr(struct dentry
*d
, const char __user
*name
)
602 char kname
[XATTR_NAME_MAX
+ 1];
604 error
= strncpy_from_user(kname
, name
, sizeof(kname
));
605 if (error
== 0 || error
== sizeof(kname
))
610 return vfs_removexattr(d
, kname
);
613 SYSCALL_DEFINE2(removexattr
, const char __user
*, pathname
,
614 const char __user
*, name
)
619 error
= user_path(pathname
, &path
);
622 error
= mnt_want_write(path
.mnt
);
624 error
= removexattr(path
.dentry
, name
);
625 mnt_drop_write(path
.mnt
);
631 SYSCALL_DEFINE2(lremovexattr
, const char __user
*, pathname
,
632 const char __user
*, name
)
637 error
= user_lpath(pathname
, &path
);
640 error
= mnt_want_write(path
.mnt
);
642 error
= removexattr(path
.dentry
, name
);
643 mnt_drop_write(path
.mnt
);
649 SYSCALL_DEFINE2(fremovexattr
, int, fd
, const char __user
*, name
)
651 struct fd f
= fdget(fd
);
652 struct dentry
*dentry
;
657 dentry
= f
.file
->f_path
.dentry
;
658 audit_inode(NULL
, dentry
, 0);
659 error
= mnt_want_write_file(f
.file
);
661 error
= removexattr(dentry
, name
);
662 mnt_drop_write_file(f
.file
);
670 strcmp_prefix(const char *a
, const char *a_prefix
)
672 while (*a_prefix
&& *a
== *a_prefix
) {
676 return *a_prefix
? NULL
: a
;
680 * In order to implement different sets of xattr operations for each xattr
681 * prefix with the generic xattr API, a filesystem should create a
682 * null-terminated array of struct xattr_handler (one for each prefix) and
683 * hang a pointer to it off of the s_xattr field of the superblock.
685 * The generic_fooxattr() functions will use this list to dispatch xattr
686 * operations to the correct xattr_handler.
688 #define for_each_xattr_handler(handlers, handler) \
689 for ((handler) = *(handlers)++; \
691 (handler) = *(handlers)++)
694 * Find the xattr_handler with the matching prefix.
696 static const struct xattr_handler
*
697 xattr_resolve_name(const struct xattr_handler
**handlers
, const char **name
)
699 const struct xattr_handler
*handler
;
704 for_each_xattr_handler(handlers
, handler
) {
705 const char *n
= strcmp_prefix(*name
, handler
->prefix
);
715 * Find the handler for the prefix and dispatch its get() operation.
718 generic_getxattr(struct dentry
*dentry
, const char *name
, void *buffer
, size_t size
)
720 const struct xattr_handler
*handler
;
722 handler
= xattr_resolve_name(dentry
->d_sb
->s_xattr
, &name
);
725 return handler
->get(dentry
, name
, buffer
, size
, handler
->flags
);
729 * Combine the results of the list() operation from every xattr_handler in the
733 generic_listxattr(struct dentry
*dentry
, char *buffer
, size_t buffer_size
)
735 const struct xattr_handler
*handler
, **handlers
= dentry
->d_sb
->s_xattr
;
736 unsigned int size
= 0;
739 for_each_xattr_handler(handlers
, handler
) {
740 size
+= handler
->list(dentry
, NULL
, 0, NULL
, 0,
746 for_each_xattr_handler(handlers
, handler
) {
747 size
= handler
->list(dentry
, buf
, buffer_size
,
748 NULL
, 0, handler
->flags
);
749 if (size
> buffer_size
)
760 * Find the handler for the prefix and dispatch its set() operation.
763 generic_setxattr(struct dentry
*dentry
, const char *name
, const void *value
, size_t size
, int flags
)
765 const struct xattr_handler
*handler
;
768 value
= ""; /* empty EA, do not remove */
769 handler
= xattr_resolve_name(dentry
->d_sb
->s_xattr
, &name
);
772 return handler
->set(dentry
, name
, value
, size
, flags
, handler
->flags
);
776 * Find the handler for the prefix and dispatch its set() operation to remove
777 * any associated extended attribute.
780 generic_removexattr(struct dentry
*dentry
, const char *name
)
782 const struct xattr_handler
*handler
;
784 handler
= xattr_resolve_name(dentry
->d_sb
->s_xattr
, &name
);
787 return handler
->set(dentry
, name
, NULL
, 0,
788 XATTR_REPLACE
, handler
->flags
);
791 EXPORT_SYMBOL(generic_getxattr
);
792 EXPORT_SYMBOL(generic_listxattr
);
793 EXPORT_SYMBOL(generic_setxattr
);
794 EXPORT_SYMBOL(generic_removexattr
);
797 * Allocate new xattr and copy in the value; but leave the name to callers.
799 struct simple_xattr
*simple_xattr_alloc(const void *value
, size_t size
)
801 struct simple_xattr
*new_xattr
;
805 len
= sizeof(*new_xattr
) + size
;
806 if (len
<= sizeof(*new_xattr
))
809 new_xattr
= kmalloc(len
, GFP_KERNEL
);
813 new_xattr
->size
= size
;
814 memcpy(new_xattr
->value
, value
, size
);
819 * xattr GET operation for in-memory/pseudo filesystems
821 int simple_xattr_get(struct simple_xattrs
*xattrs
, const char *name
,
822 void *buffer
, size_t size
)
824 struct simple_xattr
*xattr
;
827 spin_lock(&xattrs
->lock
);
828 list_for_each_entry(xattr
, &xattrs
->head
, list
) {
829 if (strcmp(name
, xattr
->name
))
834 if (size
< xattr
->size
)
837 memcpy(buffer
, xattr
->value
, xattr
->size
);
841 spin_unlock(&xattrs
->lock
);
845 static int __simple_xattr_set(struct simple_xattrs
*xattrs
, const char *name
,
846 const void *value
, size_t size
, int flags
)
848 struct simple_xattr
*xattr
;
849 struct simple_xattr
*uninitialized_var(new_xattr
);
852 /* value == NULL means remove */
854 new_xattr
= simple_xattr_alloc(value
, size
);
858 new_xattr
->name
= kstrdup(name
, GFP_KERNEL
);
859 if (!new_xattr
->name
) {
865 spin_lock(&xattrs
->lock
);
866 list_for_each_entry(xattr
, &xattrs
->head
, list
) {
867 if (!strcmp(name
, xattr
->name
)) {
868 if (flags
& XATTR_CREATE
) {
871 } else if (new_xattr
) {
872 list_replace(&xattr
->list
, &new_xattr
->list
);
874 list_del(&xattr
->list
);
879 if (flags
& XATTR_REPLACE
) {
883 list_add(&new_xattr
->list
, &xattrs
->head
);
887 spin_unlock(&xattrs
->lock
);
897 * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
898 * @xattrs: target simple_xattr list
899 * @name: name of the new extended attribute
900 * @value: value of the new xattr. If %NULL, will remove the attribute
901 * @size: size of the new xattr
902 * @flags: %XATTR_{CREATE|REPLACE}
904 * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
905 * with -EEXIST. If %XATTR_REPLACE is set, the xattr should exist;
906 * otherwise, fails with -ENODATA.
908 * Returns 0 on success, -errno on failure.
910 int simple_xattr_set(struct simple_xattrs
*xattrs
, const char *name
,
911 const void *value
, size_t size
, int flags
)
914 value
= ""; /* empty EA, do not remove */
915 return __simple_xattr_set(xattrs
, name
, value
, size
, flags
);
919 * xattr REMOVE operation for in-memory/pseudo filesystems
921 int simple_xattr_remove(struct simple_xattrs
*xattrs
, const char *name
)
923 return __simple_xattr_set(xattrs
, name
, NULL
, 0, XATTR_REPLACE
);
926 static bool xattr_is_trusted(const char *name
)
928 return !strncmp(name
, XATTR_TRUSTED_PREFIX
, XATTR_TRUSTED_PREFIX_LEN
);
932 * xattr LIST operation for in-memory/pseudo filesystems
934 ssize_t
simple_xattr_list(struct simple_xattrs
*xattrs
, char *buffer
,
937 bool trusted
= capable(CAP_SYS_ADMIN
);
938 struct simple_xattr
*xattr
;
941 spin_lock(&xattrs
->lock
);
942 list_for_each_entry(xattr
, &xattrs
->head
, list
) {
945 /* skip "trusted." attributes for unprivileged callers */
946 if (!trusted
&& xattr_is_trusted(xattr
->name
))
949 len
= strlen(xattr
->name
) + 1;
956 memcpy(buffer
, xattr
->name
, len
);
960 spin_unlock(&xattrs
->lock
);
966 * Adds an extended attribute to the list
968 void simple_xattr_list_add(struct simple_xattrs
*xattrs
,
969 struct simple_xattr
*new_xattr
)
971 spin_lock(&xattrs
->lock
);
972 list_add(&new_xattr
->list
, &xattrs
->head
);
973 spin_unlock(&xattrs
->lock
);