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>
24 #include <asm/uaccess.h>
27 * Check permissions for extended attribute access. This is a bit complicated
28 * because different namespaces have very different rules.
31 xattr_permission(struct inode
*inode
, const char *name
, int mask
)
34 * We can never set or remove an extended attribute on a read-only
35 * filesystem or on an immutable / append-only inode.
37 if (mask
& MAY_WRITE
) {
38 if (IS_IMMUTABLE(inode
) || IS_APPEND(inode
))
43 * No restriction for security.* and system.* from the VFS. Decision
44 * on these is left to the underlying filesystem / security module.
46 if (!strncmp(name
, XATTR_SECURITY_PREFIX
, XATTR_SECURITY_PREFIX_LEN
) ||
47 !strncmp(name
, XATTR_SYSTEM_PREFIX
, XATTR_SYSTEM_PREFIX_LEN
))
51 * The trusted.* namespace can only be accessed by privileged users.
53 if (!strncmp(name
, XATTR_TRUSTED_PREFIX
, XATTR_TRUSTED_PREFIX_LEN
)) {
54 if (!capable(CAP_SYS_ADMIN
))
55 return (mask
& MAY_WRITE
) ? -EPERM
: -ENODATA
;
60 * In the user.* namespace, only regular files and directories can have
61 * extended attributes. For sticky directories, only the owner and
62 * privileged users can write attributes.
64 if (!strncmp(name
, XATTR_USER_PREFIX
, XATTR_USER_PREFIX_LEN
)) {
65 if (!S_ISREG(inode
->i_mode
) && !S_ISDIR(inode
->i_mode
))
66 return (mask
& MAY_WRITE
) ? -EPERM
: -ENODATA
;
67 if (S_ISDIR(inode
->i_mode
) && (inode
->i_mode
& S_ISVTX
) &&
68 (mask
& MAY_WRITE
) && !inode_owner_or_capable(inode
))
72 return inode_permission(inode
, mask
);
76 * __vfs_setxattr_noperm - perform setxattr operation without performing
79 * @dentry - object to perform setxattr on
80 * @name - xattr name to set
81 * @value - value to set @name to
82 * @size - size of @value
83 * @flags - flags to pass into filesystem operations
85 * returns the result of the internal setxattr or setsecurity operations.
87 * This function requires the caller to lock the inode's i_mutex before it
88 * is executed. It also assumes that the caller will make the appropriate
91 int __vfs_setxattr_noperm(struct dentry
*dentry
, const char *name
,
92 const void *value
, size_t size
, int flags
)
94 struct inode
*inode
= dentry
->d_inode
;
95 int error
= -EOPNOTSUPP
;
96 int issec
= !strncmp(name
, XATTR_SECURITY_PREFIX
,
97 XATTR_SECURITY_PREFIX_LEN
);
100 inode
->i_flags
&= ~S_NOSEC
;
101 if (inode
->i_op
->setxattr
) {
102 error
= inode
->i_op
->setxattr(dentry
, name
, value
, size
, flags
);
104 fsnotify_xattr(dentry
);
105 security_inode_post_setxattr(dentry
, name
, value
,
109 const char *suffix
= name
+ XATTR_SECURITY_PREFIX_LEN
;
110 error
= security_inode_setsecurity(inode
, suffix
, value
,
113 fsnotify_xattr(dentry
);
121 vfs_setxattr(struct dentry
*dentry
, const char *name
, const void *value
,
122 size_t size
, int flags
)
124 struct inode
*inode
= dentry
->d_inode
;
127 error
= xattr_permission(inode
, name
, MAY_WRITE
);
131 mutex_lock(&inode
->i_mutex
);
132 error
= security_inode_setxattr(dentry
, name
, value
, size
, flags
);
136 error
= __vfs_setxattr_noperm(dentry
, name
, value
, size
, flags
);
139 mutex_unlock(&inode
->i_mutex
);
142 EXPORT_SYMBOL_GPL(vfs_setxattr
);
145 xattr_getsecurity(struct inode
*inode
, const char *name
, void *value
,
151 if (!value
|| !size
) {
152 len
= security_inode_getsecurity(inode
, name
, &buffer
, false);
156 len
= security_inode_getsecurity(inode
, name
, &buffer
, true);
163 memcpy(value
, buffer
, len
);
165 security_release_secctx(buffer
, len
);
169 EXPORT_SYMBOL_GPL(xattr_getsecurity
);
172 * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
174 * Allocate memory, if not already allocated, or re-allocate correct size,
175 * before retrieving the extended attribute.
177 * Returns the result of alloc, if failed, or the getxattr operation.
180 vfs_getxattr_alloc(struct dentry
*dentry
, const char *name
, char **xattr_value
,
181 size_t xattr_size
, gfp_t flags
)
183 struct inode
*inode
= dentry
->d_inode
;
184 char *value
= *xattr_value
;
187 error
= xattr_permission(inode
, name
, MAY_READ
);
191 if (!inode
->i_op
->getxattr
)
194 error
= inode
->i_op
->getxattr(dentry
, name
, NULL
, 0);
198 if (!value
|| (error
> xattr_size
)) {
199 value
= krealloc(*xattr_value
, error
+ 1, flags
);
202 memset(value
, 0, error
+ 1);
205 error
= inode
->i_op
->getxattr(dentry
, name
, value
, error
);
206 *xattr_value
= value
;
210 /* Compare an extended attribute value with the given value */
211 int vfs_xattr_cmp(struct dentry
*dentry
, const char *xattr_name
,
212 const char *value
, size_t size
, gfp_t flags
)
214 char *xattr_value
= NULL
;
217 rc
= vfs_getxattr_alloc(dentry
, xattr_name
, &xattr_value
, 0, flags
);
221 if ((rc
!= size
) || (memcmp(xattr_value
, value
, rc
) != 0))
230 vfs_getxattr(struct dentry
*dentry
, const char *name
, void *value
, size_t size
)
232 struct inode
*inode
= dentry
->d_inode
;
235 error
= xattr_permission(inode
, name
, MAY_READ
);
239 error
= security_inode_getxattr(dentry
, name
);
243 if (!strncmp(name
, XATTR_SECURITY_PREFIX
,
244 XATTR_SECURITY_PREFIX_LEN
)) {
245 const char *suffix
= name
+ XATTR_SECURITY_PREFIX_LEN
;
246 int ret
= xattr_getsecurity(inode
, suffix
, value
, size
);
248 * Only overwrite the return value if a security module
249 * is actually active.
251 if (ret
== -EOPNOTSUPP
)
256 if (inode
->i_op
->getxattr
)
257 error
= inode
->i_op
->getxattr(dentry
, name
, value
, size
);
263 EXPORT_SYMBOL_GPL(vfs_getxattr
);
266 vfs_listxattr(struct dentry
*d
, char *list
, size_t size
)
270 error
= security_inode_listxattr(d
);
274 if (d
->d_inode
->i_op
->listxattr
) {
275 error
= d
->d_inode
->i_op
->listxattr(d
, list
, size
);
277 error
= security_inode_listsecurity(d
->d_inode
, list
, size
);
278 if (size
&& error
> size
)
283 EXPORT_SYMBOL_GPL(vfs_listxattr
);
286 vfs_removexattr(struct dentry
*dentry
, const char *name
)
288 struct inode
*inode
= dentry
->d_inode
;
291 if (!inode
->i_op
->removexattr
)
294 error
= xattr_permission(inode
, name
, MAY_WRITE
);
298 mutex_lock(&inode
->i_mutex
);
299 error
= security_inode_removexattr(dentry
, name
);
301 mutex_unlock(&inode
->i_mutex
);
305 error
= inode
->i_op
->removexattr(dentry
, name
);
306 mutex_unlock(&inode
->i_mutex
);
309 fsnotify_xattr(dentry
);
310 evm_inode_post_removexattr(dentry
, name
);
314 EXPORT_SYMBOL_GPL(vfs_removexattr
);
318 * Extended attribute SET operations
321 setxattr(struct dentry
*d
, const char __user
*name
, const void __user
*value
,
322 size_t size
, int flags
)
326 void *vvalue
= NULL
; /* If non-NULL, we used vmalloc() */
327 char kname
[XATTR_NAME_MAX
+ 1];
329 if (flags
& ~(XATTR_CREATE
|XATTR_REPLACE
))
332 error
= strncpy_from_user(kname
, name
, sizeof(kname
));
333 if (error
== 0 || error
== sizeof(kname
))
339 if (size
> XATTR_SIZE_MAX
)
341 kvalue
= kmalloc(size
, GFP_KERNEL
| __GFP_NOWARN
);
343 vvalue
= vmalloc(size
);
348 if (copy_from_user(kvalue
, value
, size
)) {
354 error
= vfs_setxattr(d
, kname
, kvalue
, size
, flags
);
363 SYSCALL_DEFINE5(setxattr
, const char __user
*, pathname
,
364 const char __user
*, name
, const void __user
*, value
,
365 size_t, size
, int, flags
)
370 error
= user_path(pathname
, &path
);
373 error
= mnt_want_write(path
.mnt
);
375 error
= setxattr(path
.dentry
, name
, value
, size
, flags
);
376 mnt_drop_write(path
.mnt
);
382 SYSCALL_DEFINE5(lsetxattr
, const char __user
*, pathname
,
383 const char __user
*, name
, const void __user
*, value
,
384 size_t, size
, int, flags
)
389 error
= user_lpath(pathname
, &path
);
392 error
= mnt_want_write(path
.mnt
);
394 error
= setxattr(path
.dentry
, name
, value
, size
, flags
);
395 mnt_drop_write(path
.mnt
);
401 SYSCALL_DEFINE5(fsetxattr
, int, fd
, const char __user
*, name
,
402 const void __user
*,value
, size_t, size
, int, flags
)
406 struct dentry
*dentry
;
409 f
= fget_light(fd
, &fput_needed
);
412 dentry
= f
->f_path
.dentry
;
413 audit_inode(NULL
, dentry
);
414 error
= mnt_want_write_file(f
);
416 error
= setxattr(dentry
, name
, value
, size
, flags
);
417 mnt_drop_write_file(f
);
419 fput_light(f
, fput_needed
);
424 * Extended attribute GET operations
427 getxattr(struct dentry
*d
, const char __user
*name
, void __user
*value
,
433 char kname
[XATTR_NAME_MAX
+ 1];
435 error
= strncpy_from_user(kname
, name
, sizeof(kname
));
436 if (error
== 0 || error
== sizeof(kname
))
442 if (size
> XATTR_SIZE_MAX
)
443 size
= XATTR_SIZE_MAX
;
444 kvalue
= kzalloc(size
, GFP_KERNEL
| __GFP_NOWARN
);
446 vvalue
= vmalloc(size
);
453 error
= vfs_getxattr(d
, kname
, kvalue
, size
);
455 if (size
&& copy_to_user(value
, kvalue
, error
))
457 } else if (error
== -ERANGE
&& size
>= XATTR_SIZE_MAX
) {
458 /* The file system tried to returned a value bigger
459 than XATTR_SIZE_MAX bytes. Not possible. */
469 SYSCALL_DEFINE4(getxattr
, const char __user
*, pathname
,
470 const char __user
*, name
, void __user
*, value
, size_t, size
)
475 error
= user_path(pathname
, &path
);
478 error
= getxattr(path
.dentry
, name
, value
, size
);
483 SYSCALL_DEFINE4(lgetxattr
, const char __user
*, pathname
,
484 const char __user
*, name
, void __user
*, value
, size_t, size
)
489 error
= user_lpath(pathname
, &path
);
492 error
= getxattr(path
.dentry
, name
, value
, size
);
497 SYSCALL_DEFINE4(fgetxattr
, int, fd
, const char __user
*, name
,
498 void __user
*, value
, size_t, size
)
502 ssize_t error
= -EBADF
;
504 f
= fget_light(fd
, &fput_needed
);
507 audit_inode(NULL
, f
->f_path
.dentry
);
508 error
= getxattr(f
->f_path
.dentry
, name
, value
, size
);
509 fput_light(f
, fput_needed
);
514 * Extended attribute LIST operations
517 listxattr(struct dentry
*d
, char __user
*list
, size_t size
)
521 char *vlist
= NULL
; /* If non-NULL, we used vmalloc() */
524 if (size
> XATTR_LIST_MAX
)
525 size
= XATTR_LIST_MAX
;
526 klist
= kmalloc(size
, __GFP_NOWARN
| GFP_KERNEL
);
528 vlist
= vmalloc(size
);
535 error
= vfs_listxattr(d
, klist
, size
);
537 if (size
&& copy_to_user(list
, klist
, error
))
539 } else if (error
== -ERANGE
&& size
>= XATTR_LIST_MAX
) {
540 /* The file system tried to returned a list bigger
541 than XATTR_LIST_MAX bytes. Not possible. */
551 SYSCALL_DEFINE3(listxattr
, const char __user
*, pathname
, char __user
*, list
,
557 error
= user_path(pathname
, &path
);
560 error
= listxattr(path
.dentry
, list
, size
);
565 SYSCALL_DEFINE3(llistxattr
, const char __user
*, pathname
, char __user
*, list
,
571 error
= user_lpath(pathname
, &path
);
574 error
= listxattr(path
.dentry
, list
, size
);
579 SYSCALL_DEFINE3(flistxattr
, int, fd
, char __user
*, list
, size_t, size
)
583 ssize_t error
= -EBADF
;
585 f
= fget_light(fd
, &fput_needed
);
588 audit_inode(NULL
, f
->f_path
.dentry
);
589 error
= listxattr(f
->f_path
.dentry
, list
, size
);
590 fput_light(f
, fput_needed
);
595 * Extended attribute REMOVE operations
598 removexattr(struct dentry
*d
, const char __user
*name
)
601 char kname
[XATTR_NAME_MAX
+ 1];
603 error
= strncpy_from_user(kname
, name
, sizeof(kname
));
604 if (error
== 0 || error
== sizeof(kname
))
609 return vfs_removexattr(d
, kname
);
612 SYSCALL_DEFINE2(removexattr
, const char __user
*, pathname
,
613 const char __user
*, name
)
618 error
= user_path(pathname
, &path
);
621 error
= mnt_want_write(path
.mnt
);
623 error
= removexattr(path
.dentry
, name
);
624 mnt_drop_write(path
.mnt
);
630 SYSCALL_DEFINE2(lremovexattr
, const char __user
*, pathname
,
631 const char __user
*, name
)
636 error
= user_lpath(pathname
, &path
);
639 error
= mnt_want_write(path
.mnt
);
641 error
= removexattr(path
.dentry
, name
);
642 mnt_drop_write(path
.mnt
);
648 SYSCALL_DEFINE2(fremovexattr
, int, fd
, const char __user
*, name
)
652 struct dentry
*dentry
;
655 f
= fget_light(fd
, &fput_needed
);
658 dentry
= f
->f_path
.dentry
;
659 audit_inode(NULL
, dentry
);
660 error
= mnt_want_write_file(f
);
662 error
= removexattr(dentry
, name
);
663 mnt_drop_write_file(f
);
665 fput_light(f
, fput_needed
);
671 strcmp_prefix(const char *a
, const char *a_prefix
)
673 while (*a_prefix
&& *a
== *a_prefix
) {
677 return *a_prefix
? NULL
: a
;
681 * In order to implement different sets of xattr operations for each xattr
682 * prefix with the generic xattr API, a filesystem should create a
683 * null-terminated array of struct xattr_handler (one for each prefix) and
684 * hang a pointer to it off of the s_xattr field of the superblock.
686 * The generic_fooxattr() functions will use this list to dispatch xattr
687 * operations to the correct xattr_handler.
689 #define for_each_xattr_handler(handlers, handler) \
690 for ((handler) = *(handlers)++; \
692 (handler) = *(handlers)++)
695 * Find the xattr_handler with the matching prefix.
697 static const struct xattr_handler
*
698 xattr_resolve_name(const struct xattr_handler
**handlers
, const char **name
)
700 const struct xattr_handler
*handler
;
705 for_each_xattr_handler(handlers
, handler
) {
706 const char *n
= strcmp_prefix(*name
, handler
->prefix
);
716 * Find the handler for the prefix and dispatch its get() operation.
719 generic_getxattr(struct dentry
*dentry
, const char *name
, void *buffer
, size_t size
)
721 const struct xattr_handler
*handler
;
723 handler
= xattr_resolve_name(dentry
->d_sb
->s_xattr
, &name
);
726 return handler
->get(dentry
, name
, buffer
, size
, handler
->flags
);
730 * Combine the results of the list() operation from every xattr_handler in the
734 generic_listxattr(struct dentry
*dentry
, char *buffer
, size_t buffer_size
)
736 const struct xattr_handler
*handler
, **handlers
= dentry
->d_sb
->s_xattr
;
737 unsigned int size
= 0;
740 for_each_xattr_handler(handlers
, handler
) {
741 size
+= handler
->list(dentry
, NULL
, 0, NULL
, 0,
747 for_each_xattr_handler(handlers
, handler
) {
748 size
= handler
->list(dentry
, buf
, buffer_size
,
749 NULL
, 0, handler
->flags
);
750 if (size
> buffer_size
)
761 * Find the handler for the prefix and dispatch its set() operation.
764 generic_setxattr(struct dentry
*dentry
, const char *name
, const void *value
, size_t size
, int flags
)
766 const struct xattr_handler
*handler
;
769 value
= ""; /* empty EA, do not remove */
770 handler
= xattr_resolve_name(dentry
->d_sb
->s_xattr
, &name
);
773 return handler
->set(dentry
, name
, value
, size
, flags
, handler
->flags
);
777 * Find the handler for the prefix and dispatch its set() operation to remove
778 * any associated extended attribute.
781 generic_removexattr(struct dentry
*dentry
, const char *name
)
783 const struct xattr_handler
*handler
;
785 handler
= xattr_resolve_name(dentry
->d_sb
->s_xattr
, &name
);
788 return handler
->set(dentry
, name
, NULL
, 0,
789 XATTR_REPLACE
, handler
->flags
);
792 EXPORT_SYMBOL(generic_getxattr
);
793 EXPORT_SYMBOL(generic_listxattr
);
794 EXPORT_SYMBOL(generic_setxattr
);
795 EXPORT_SYMBOL(generic_removexattr
);