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);
304 error = inode->i_op->removexattr(dentry, name);
307 fsnotify_xattr(dentry);
308 evm_inode_post_removexattr(dentry, name);
312 mutex_unlock(&inode->i_mutex);
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 static int path_setxattr(const char __user *pathname,
368 const char __user *name, const void __user *value,
369 size_t size, int flags, unsigned int lookup_flags)
374 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
377 error = mnt_want_write(path.mnt);
379 error = setxattr(path.dentry, name, value, size, flags);
380 mnt_drop_write(path.mnt);
383 if (retry_estale(error, lookup_flags)) {
384 lookup_flags |= LOOKUP_REVAL;
390 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
391 const char __user *, name, const void __user *, value,
392 size_t, size, int, flags)
394 return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
397 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
398 const char __user *, name, const void __user *, value,
399 size_t, size, int, flags)
401 return path_setxattr(pathname, name, value, size, flags, 0);
404 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
405 const void __user *,value, size_t, size, int, flags)
407 struct fd f = fdget(fd);
413 error = mnt_want_write_file(f.file);
415 error = setxattr(f.file->f_path.dentry, name, value, size, flags);
416 mnt_drop_write_file(f.file);
423 * Extended attribute GET operations
426 getxattr(struct dentry *d, const char __user *name, void __user *value,
432 char kname[XATTR_NAME_MAX + 1];
434 error = strncpy_from_user(kname, name, sizeof(kname));
435 if (error == 0 || error == sizeof(kname))
441 if (size > XATTR_SIZE_MAX)
442 size = XATTR_SIZE_MAX;
443 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
445 vvalue = vmalloc(size);
452 error = vfs_getxattr(d, kname, kvalue, size);
454 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
455 (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
456 posix_acl_fix_xattr_to_user(kvalue, size);
457 if (size && copy_to_user(value, kvalue, error))
459 } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
460 /* The file system tried to returned a value bigger
461 than XATTR_SIZE_MAX bytes. Not possible. */
471 static ssize_t path_getxattr(const char __user *pathname,
472 const char __user *name, void __user *value,
473 size_t size, unsigned int lookup_flags)
478 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
481 error = getxattr(path.dentry, name, value, size);
483 if (retry_estale(error, lookup_flags)) {
484 lookup_flags |= LOOKUP_REVAL;
490 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
491 const char __user *, name, void __user *, value, size_t, size)
493 return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
496 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
497 const char __user *, name, void __user *, value, size_t, size)
499 return path_getxattr(pathname, name, value, size, 0);
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;
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 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
555 size_t size, unsigned int lookup_flags)
560 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
563 error = listxattr(path.dentry, list, size);
565 if (retry_estale(error, lookup_flags)) {
566 lookup_flags |= LOOKUP_REVAL;
572 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
575 return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
578 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
581 return path_listxattr(pathname, list, size, 0);
584 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
586 struct fd f = fdget(fd);
587 ssize_t error = -EBADF;
592 error = listxattr(f.file->f_path.dentry, list, size);
598 * Extended attribute REMOVE operations
601 removexattr(struct dentry *d, const char __user *name)
604 char kname[XATTR_NAME_MAX + 1];
606 error = strncpy_from_user(kname, name, sizeof(kname));
607 if (error == 0 || error == sizeof(kname))
612 return vfs_removexattr(d, kname);
615 static int path_removexattr(const char __user *pathname,
616 const char __user *name, unsigned int lookup_flags)
621 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
624 error = mnt_want_write(path.mnt);
626 error = removexattr(path.dentry, name);
627 mnt_drop_write(path.mnt);
630 if (retry_estale(error, lookup_flags)) {
631 lookup_flags |= LOOKUP_REVAL;
637 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
638 const char __user *, name)
640 return path_removexattr(pathname, name, LOOKUP_FOLLOW);
643 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
644 const char __user *, name)
646 return path_removexattr(pathname, name, 0);
649 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
651 struct fd f = fdget(fd);
657 error = mnt_want_write_file(f.file);
659 error = removexattr(f.file->f_path.dentry, name);
660 mnt_drop_write_file(f.file);
668 strcmp_prefix(const char *a, const char *a_prefix)
670 while (*a_prefix && *a == *a_prefix) {
674 return *a_prefix ? NULL : a;
678 * In order to implement different sets of xattr operations for each xattr
679 * prefix with the generic xattr API, a filesystem should create a
680 * null-terminated array of struct xattr_handler (one for each prefix) and
681 * hang a pointer to it off of the s_xattr field of the superblock.
683 * The generic_fooxattr() functions will use this list to dispatch xattr
684 * operations to the correct xattr_handler.
686 #define for_each_xattr_handler(handlers, handler) \
687 for ((handler) = *(handlers)++; \
689 (handler) = *(handlers)++)
692 * Find the xattr_handler with the matching prefix.
694 static const struct xattr_handler *
695 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
697 const struct xattr_handler *handler;
702 for_each_xattr_handler(handlers, handler) {
703 const char *n = strcmp_prefix(*name, handler->prefix);
713 * Find the handler for the prefix and dispatch its get() operation.
716 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
718 const struct xattr_handler *handler;
720 handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
723 return handler->get(handler, dentry, name, buffer, size);
727 * Combine the results of the list() operation from every xattr_handler in the
731 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
733 const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
734 unsigned int size = 0;
737 for_each_xattr_handler(handlers, handler) {
738 size += handler->list(handler, dentry, NULL, 0,
744 for_each_xattr_handler(handlers, handler) {
745 size = handler->list(handler, dentry, buf, buffer_size,
747 if (size > buffer_size)
758 * Find the handler for the prefix and dispatch its set() operation.
761 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
763 const struct xattr_handler *handler;
766 value = ""; /* empty EA, do not remove */
767 handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
770 return handler->set(handler, dentry, name, value, size, flags);
774 * Find the handler for the prefix and dispatch its set() operation to remove
775 * any associated extended attribute.
778 generic_removexattr(struct dentry *dentry, const char *name)
780 const struct xattr_handler *handler;
782 handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
785 return handler->set(handler, dentry, name, NULL, 0, XATTR_REPLACE);
788 EXPORT_SYMBOL(generic_getxattr);
789 EXPORT_SYMBOL(generic_listxattr);
790 EXPORT_SYMBOL(generic_setxattr);
791 EXPORT_SYMBOL(generic_removexattr);
794 * xattr_full_name - Compute full attribute name from suffix
796 * @handler: handler of the xattr_handler operation
797 * @name: name passed to the xattr_handler operation
799 * The get and set xattr handler operations are called with the remainder of
800 * the attribute name after skipping the handler's prefix: for example, "foo"
801 * is passed to the get operation of a handler with prefix "user." to get
802 * attribute "user.foo". The full name is still "there" in the name though.
804 * Note: the list xattr handler operation when called from the vfs is passed a
805 * NULL name; some file systems use this operation internally, with varying
808 const char *xattr_full_name(const struct xattr_handler *handler,
811 size_t prefix_len = strlen(handler->prefix);
813 return name - prefix_len;
815 EXPORT_SYMBOL(xattr_full_name);
818 * Allocate new xattr and copy in the value; but leave the name to callers.
820 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
822 struct simple_xattr *new_xattr;
826 len = sizeof(*new_xattr) + size;
827 if (len < sizeof(*new_xattr))
830 new_xattr = kmalloc(len, GFP_KERNEL);
834 new_xattr->size = size;
835 memcpy(new_xattr->value, value, size);
840 * xattr GET operation for in-memory/pseudo filesystems
842 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
843 void *buffer, size_t size)
845 struct simple_xattr *xattr;
848 spin_lock(&xattrs->lock);
849 list_for_each_entry(xattr, &xattrs->head, list) {
850 if (strcmp(name, xattr->name))
855 if (size < xattr->size)
858 memcpy(buffer, xattr->value, xattr->size);
862 spin_unlock(&xattrs->lock);
866 static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
867 const void *value, size_t size, int flags)
869 struct simple_xattr *xattr;
870 struct simple_xattr *new_xattr = NULL;
873 /* value == NULL means remove */
875 new_xattr = simple_xattr_alloc(value, size);
879 new_xattr->name = kstrdup(name, GFP_KERNEL);
880 if (!new_xattr->name) {
886 spin_lock(&xattrs->lock);
887 list_for_each_entry(xattr, &xattrs->head, list) {
888 if (!strcmp(name, xattr->name)) {
889 if (flags & XATTR_CREATE) {
892 } else if (new_xattr) {
893 list_replace(&xattr->list, &new_xattr->list);
895 list_del(&xattr->list);
900 if (flags & XATTR_REPLACE) {
904 list_add(&new_xattr->list, &xattrs->head);
908 spin_unlock(&xattrs->lock);
918 * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
919 * @xattrs: target simple_xattr list
920 * @name: name of the new extended attribute
921 * @value: value of the new xattr. If %NULL, will remove the attribute
922 * @size: size of the new xattr
923 * @flags: %XATTR_{CREATE|REPLACE}
925 * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
926 * with -EEXIST. If %XATTR_REPLACE is set, the xattr should exist;
927 * otherwise, fails with -ENODATA.
929 * Returns 0 on success, -errno on failure.
931 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
932 const void *value, size_t size, int flags)
935 value = ""; /* empty EA, do not remove */
936 return __simple_xattr_set(xattrs, name, value, size, flags);
940 * xattr REMOVE operation for in-memory/pseudo filesystems
942 int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
944 return __simple_xattr_set(xattrs, name, NULL, 0, XATTR_REPLACE);
947 static bool xattr_is_trusted(const char *name)
949 return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
953 * xattr LIST operation for in-memory/pseudo filesystems
955 ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer,
958 bool trusted = capable(CAP_SYS_ADMIN);
959 struct simple_xattr *xattr;
962 spin_lock(&xattrs->lock);
963 list_for_each_entry(xattr, &xattrs->head, list) {
966 /* skip "trusted." attributes for unprivileged callers */
967 if (!trusted && xattr_is_trusted(xattr->name))
970 len = strlen(xattr->name) + 1;
977 memcpy(buffer, xattr->name, len);
981 spin_unlock(&xattrs->lock);
987 * Adds an extended attribute to the list
989 void simple_xattr_list_add(struct simple_xattrs *xattrs,
990 struct simple_xattr *new_xattr)
992 spin_lock(&xattrs->lock);
993 list_add(&new_xattr->list, &xattrs->head);
994 spin_unlock(&xattrs->lock);