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
)
373 unsigned int lookup_flags
= LOOKUP_FOLLOW
;
375 error
= user_path_at(AT_FDCWD
, pathname
, lookup_flags
, &path
);
378 error
= mnt_want_write(path
.mnt
);
380 error
= setxattr(path
.dentry
, name
, value
, size
, flags
);
381 mnt_drop_write(path
.mnt
);
384 if (retry_estale(error
, lookup_flags
)) {
385 lookup_flags
|= LOOKUP_REVAL
;
391 SYSCALL_DEFINE5(lsetxattr
, const char __user
*, pathname
,
392 const char __user
*, name
, const void __user
*, value
,
393 size_t, size
, int, flags
)
397 unsigned int lookup_flags
= 0;
399 error
= user_path_at(AT_FDCWD
, pathname
, lookup_flags
, &path
);
402 error
= mnt_want_write(path
.mnt
);
404 error
= setxattr(path
.dentry
, name
, value
, size
, flags
);
405 mnt_drop_write(path
.mnt
);
408 if (retry_estale(error
, lookup_flags
)) {
409 lookup_flags
|= LOOKUP_REVAL
;
415 SYSCALL_DEFINE5(fsetxattr
, int, fd
, const char __user
*, name
,
416 const void __user
*,value
, size_t, size
, int, flags
)
418 struct fd f
= fdget(fd
);
419 struct dentry
*dentry
;
424 dentry
= f
.file
->f_path
.dentry
;
425 audit_inode(NULL
, dentry
, 0);
426 error
= mnt_want_write_file(f
.file
);
428 error
= setxattr(dentry
, name
, value
, size
, flags
);
429 mnt_drop_write_file(f
.file
);
436 * Extended attribute GET operations
439 getxattr(struct dentry
*d
, const char __user
*name
, void __user
*value
,
445 char kname
[XATTR_NAME_MAX
+ 1];
447 error
= strncpy_from_user(kname
, name
, sizeof(kname
));
448 if (error
== 0 || error
== sizeof(kname
))
454 if (size
> XATTR_SIZE_MAX
)
455 size
= XATTR_SIZE_MAX
;
456 kvalue
= kzalloc(size
, GFP_KERNEL
| __GFP_NOWARN
);
458 vvalue
= vmalloc(size
);
465 error
= vfs_getxattr(d
, kname
, kvalue
, size
);
467 if ((strcmp(kname
, XATTR_NAME_POSIX_ACL_ACCESS
) == 0) ||
468 (strcmp(kname
, XATTR_NAME_POSIX_ACL_DEFAULT
) == 0))
469 posix_acl_fix_xattr_to_user(kvalue
, size
);
470 if (size
&& copy_to_user(value
, kvalue
, error
))
472 } else if (error
== -ERANGE
&& size
>= XATTR_SIZE_MAX
) {
473 /* The file system tried to returned a value bigger
474 than XATTR_SIZE_MAX bytes. Not possible. */
484 SYSCALL_DEFINE4(getxattr
, const char __user
*, pathname
,
485 const char __user
*, name
, void __user
*, value
, size_t, size
)
490 error
= user_path(pathname
, &path
);
493 error
= getxattr(path
.dentry
, name
, value
, size
);
498 SYSCALL_DEFINE4(lgetxattr
, const char __user
*, pathname
,
499 const char __user
*, name
, void __user
*, value
, size_t, size
)
504 error
= user_lpath(pathname
, &path
);
507 error
= getxattr(path
.dentry
, name
, value
, size
);
512 SYSCALL_DEFINE4(fgetxattr
, int, fd
, const char __user
*, name
,
513 void __user
*, value
, size_t, size
)
515 struct fd f
= fdget(fd
);
516 ssize_t error
= -EBADF
;
520 audit_inode(NULL
, f
.file
->f_path
.dentry
, 0);
521 error
= getxattr(f
.file
->f_path
.dentry
, name
, value
, size
);
527 * Extended attribute LIST operations
530 listxattr(struct dentry
*d
, char __user
*list
, size_t size
)
534 char *vlist
= NULL
; /* If non-NULL, we used vmalloc() */
537 if (size
> XATTR_LIST_MAX
)
538 size
= XATTR_LIST_MAX
;
539 klist
= kmalloc(size
, __GFP_NOWARN
| GFP_KERNEL
);
541 vlist
= vmalloc(size
);
548 error
= vfs_listxattr(d
, klist
, size
);
550 if (size
&& copy_to_user(list
, klist
, error
))
552 } else if (error
== -ERANGE
&& size
>= XATTR_LIST_MAX
) {
553 /* The file system tried to returned a list bigger
554 than XATTR_LIST_MAX bytes. Not possible. */
564 SYSCALL_DEFINE3(listxattr
, const char __user
*, pathname
, char __user
*, list
,
570 error
= user_path(pathname
, &path
);
573 error
= listxattr(path
.dentry
, list
, size
);
578 SYSCALL_DEFINE3(llistxattr
, const char __user
*, pathname
, char __user
*, list
,
584 error
= user_lpath(pathname
, &path
);
587 error
= listxattr(path
.dentry
, list
, size
);
592 SYSCALL_DEFINE3(flistxattr
, int, fd
, char __user
*, list
, size_t, size
)
594 struct fd f
= fdget(fd
);
595 ssize_t error
= -EBADF
;
599 audit_inode(NULL
, f
.file
->f_path
.dentry
, 0);
600 error
= listxattr(f
.file
->f_path
.dentry
, list
, size
);
606 * Extended attribute REMOVE operations
609 removexattr(struct dentry
*d
, const char __user
*name
)
612 char kname
[XATTR_NAME_MAX
+ 1];
614 error
= strncpy_from_user(kname
, name
, sizeof(kname
));
615 if (error
== 0 || error
== sizeof(kname
))
620 return vfs_removexattr(d
, kname
);
623 SYSCALL_DEFINE2(removexattr
, const char __user
*, pathname
,
624 const char __user
*, name
)
629 error
= user_path(pathname
, &path
);
632 error
= mnt_want_write(path
.mnt
);
634 error
= removexattr(path
.dentry
, name
);
635 mnt_drop_write(path
.mnt
);
641 SYSCALL_DEFINE2(lremovexattr
, const char __user
*, pathname
,
642 const char __user
*, name
)
647 error
= user_lpath(pathname
, &path
);
650 error
= mnt_want_write(path
.mnt
);
652 error
= removexattr(path
.dentry
, name
);
653 mnt_drop_write(path
.mnt
);
659 SYSCALL_DEFINE2(fremovexattr
, int, fd
, const char __user
*, name
)
661 struct fd f
= fdget(fd
);
662 struct dentry
*dentry
;
667 dentry
= f
.file
->f_path
.dentry
;
668 audit_inode(NULL
, dentry
, 0);
669 error
= mnt_want_write_file(f
.file
);
671 error
= removexattr(dentry
, name
);
672 mnt_drop_write_file(f
.file
);
680 strcmp_prefix(const char *a
, const char *a_prefix
)
682 while (*a_prefix
&& *a
== *a_prefix
) {
686 return *a_prefix
? NULL
: a
;
690 * In order to implement different sets of xattr operations for each xattr
691 * prefix with the generic xattr API, a filesystem should create a
692 * null-terminated array of struct xattr_handler (one for each prefix) and
693 * hang a pointer to it off of the s_xattr field of the superblock.
695 * The generic_fooxattr() functions will use this list to dispatch xattr
696 * operations to the correct xattr_handler.
698 #define for_each_xattr_handler(handlers, handler) \
699 for ((handler) = *(handlers)++; \
701 (handler) = *(handlers)++)
704 * Find the xattr_handler with the matching prefix.
706 static const struct xattr_handler
*
707 xattr_resolve_name(const struct xattr_handler
**handlers
, const char **name
)
709 const struct xattr_handler
*handler
;
714 for_each_xattr_handler(handlers
, handler
) {
715 const char *n
= strcmp_prefix(*name
, handler
->prefix
);
725 * Find the handler for the prefix and dispatch its get() operation.
728 generic_getxattr(struct dentry
*dentry
, const char *name
, void *buffer
, size_t size
)
730 const struct xattr_handler
*handler
;
732 handler
= xattr_resolve_name(dentry
->d_sb
->s_xattr
, &name
);
735 return handler
->get(dentry
, name
, buffer
, size
, handler
->flags
);
739 * Combine the results of the list() operation from every xattr_handler in the
743 generic_listxattr(struct dentry
*dentry
, char *buffer
, size_t buffer_size
)
745 const struct xattr_handler
*handler
, **handlers
= dentry
->d_sb
->s_xattr
;
746 unsigned int size
= 0;
749 for_each_xattr_handler(handlers
, handler
) {
750 size
+= handler
->list(dentry
, NULL
, 0, NULL
, 0,
756 for_each_xattr_handler(handlers
, handler
) {
757 size
= handler
->list(dentry
, buf
, buffer_size
,
758 NULL
, 0, handler
->flags
);
759 if (size
> buffer_size
)
770 * Find the handler for the prefix and dispatch its set() operation.
773 generic_setxattr(struct dentry
*dentry
, const char *name
, const void *value
, size_t size
, int flags
)
775 const struct xattr_handler
*handler
;
778 value
= ""; /* empty EA, do not remove */
779 handler
= xattr_resolve_name(dentry
->d_sb
->s_xattr
, &name
);
782 return handler
->set(dentry
, name
, value
, size
, flags
, handler
->flags
);
786 * Find the handler for the prefix and dispatch its set() operation to remove
787 * any associated extended attribute.
790 generic_removexattr(struct dentry
*dentry
, const char *name
)
792 const struct xattr_handler
*handler
;
794 handler
= xattr_resolve_name(dentry
->d_sb
->s_xattr
, &name
);
797 return handler
->set(dentry
, name
, NULL
, 0,
798 XATTR_REPLACE
, handler
->flags
);
801 EXPORT_SYMBOL(generic_getxattr
);
802 EXPORT_SYMBOL(generic_listxattr
);
803 EXPORT_SYMBOL(generic_setxattr
);
804 EXPORT_SYMBOL(generic_removexattr
);
807 * Allocate new xattr and copy in the value; but leave the name to callers.
809 struct simple_xattr
*simple_xattr_alloc(const void *value
, size_t size
)
811 struct simple_xattr
*new_xattr
;
815 len
= sizeof(*new_xattr
) + size
;
816 if (len
<= sizeof(*new_xattr
))
819 new_xattr
= kmalloc(len
, GFP_KERNEL
);
823 new_xattr
->size
= size
;
824 memcpy(new_xattr
->value
, value
, size
);
829 * xattr GET operation for in-memory/pseudo filesystems
831 int simple_xattr_get(struct simple_xattrs
*xattrs
, const char *name
,
832 void *buffer
, size_t size
)
834 struct simple_xattr
*xattr
;
837 spin_lock(&xattrs
->lock
);
838 list_for_each_entry(xattr
, &xattrs
->head
, list
) {
839 if (strcmp(name
, xattr
->name
))
844 if (size
< xattr
->size
)
847 memcpy(buffer
, xattr
->value
, xattr
->size
);
851 spin_unlock(&xattrs
->lock
);
855 static int __simple_xattr_set(struct simple_xattrs
*xattrs
, const char *name
,
856 const void *value
, size_t size
, int flags
)
858 struct simple_xattr
*xattr
;
859 struct simple_xattr
*new_xattr
= NULL
;
862 /* value == NULL means remove */
864 new_xattr
= simple_xattr_alloc(value
, size
);
868 new_xattr
->name
= kstrdup(name
, GFP_KERNEL
);
869 if (!new_xattr
->name
) {
875 spin_lock(&xattrs
->lock
);
876 list_for_each_entry(xattr
, &xattrs
->head
, list
) {
877 if (!strcmp(name
, xattr
->name
)) {
878 if (flags
& XATTR_CREATE
) {
881 } else if (new_xattr
) {
882 list_replace(&xattr
->list
, &new_xattr
->list
);
884 list_del(&xattr
->list
);
889 if (flags
& XATTR_REPLACE
) {
893 list_add(&new_xattr
->list
, &xattrs
->head
);
897 spin_unlock(&xattrs
->lock
);
907 * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
908 * @xattrs: target simple_xattr list
909 * @name: name of the new extended attribute
910 * @value: value of the new xattr. If %NULL, will remove the attribute
911 * @size: size of the new xattr
912 * @flags: %XATTR_{CREATE|REPLACE}
914 * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
915 * with -EEXIST. If %XATTR_REPLACE is set, the xattr should exist;
916 * otherwise, fails with -ENODATA.
918 * Returns 0 on success, -errno on failure.
920 int simple_xattr_set(struct simple_xattrs
*xattrs
, const char *name
,
921 const void *value
, size_t size
, int flags
)
924 value
= ""; /* empty EA, do not remove */
925 return __simple_xattr_set(xattrs
, name
, value
, size
, flags
);
929 * xattr REMOVE operation for in-memory/pseudo filesystems
931 int simple_xattr_remove(struct simple_xattrs
*xattrs
, const char *name
)
933 return __simple_xattr_set(xattrs
, name
, NULL
, 0, XATTR_REPLACE
);
936 static bool xattr_is_trusted(const char *name
)
938 return !strncmp(name
, XATTR_TRUSTED_PREFIX
, XATTR_TRUSTED_PREFIX_LEN
);
942 * xattr LIST operation for in-memory/pseudo filesystems
944 ssize_t
simple_xattr_list(struct simple_xattrs
*xattrs
, char *buffer
,
947 bool trusted
= capable(CAP_SYS_ADMIN
);
948 struct simple_xattr
*xattr
;
951 spin_lock(&xattrs
->lock
);
952 list_for_each_entry(xattr
, &xattrs
->head
, list
) {
955 /* skip "trusted." attributes for unprivileged callers */
956 if (!trusted
&& xattr_is_trusted(xattr
->name
))
959 len
= strlen(xattr
->name
) + 1;
966 memcpy(buffer
, xattr
->name
, len
);
970 spin_unlock(&xattrs
->lock
);
976 * Adds an extended attribute to the list
978 void simple_xattr_list_add(struct simple_xattrs
*xattrs
,
979 struct simple_xattr
*new_xattr
)
981 spin_lock(&xattrs
->lock
);
982 list_add(&new_xattr
->list
, &xattrs
->head
);
983 spin_unlock(&xattrs
->lock
);