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 <linux/uaccess.h>
29 strcmp_prefix(const char *a, const char *a_prefix)
31 while (*a_prefix && *a == *a_prefix) {
35 return *a_prefix ? NULL : a;
39 * In order to implement different sets of xattr operations for each xattr
40 * prefix, a filesystem should create a null-terminated array of struct
41 * xattr_handler (one for each prefix) and hang a pointer to it off of the
42 * s_xattr field of the superblock.
44 #define for_each_xattr_handler(handlers, handler) \
46 for ((handler) = *(handlers)++; \
48 (handler) = *(handlers)++)
51 * Find the xattr_handler with the matching prefix.
53 static const struct xattr_handler *
54 xattr_resolve_name(struct inode *inode, const char **name)
56 const struct xattr_handler **handlers = inode->i_sb->s_xattr;
57 const struct xattr_handler *handler;
59 if (!(inode->i_opflags & IOP_XATTR)) {
60 if (unlikely(is_bad_inode(inode)))
62 return ERR_PTR(-EOPNOTSUPP);
64 for_each_xattr_handler(handlers, handler) {
67 n = strcmp_prefix(*name, xattr_prefix(handler));
69 if (!handler->prefix ^ !*n) {
72 return ERR_PTR(-EINVAL);
78 return ERR_PTR(-EOPNOTSUPP);
82 * Check permissions for extended attribute access. This is a bit complicated
83 * because different namespaces have very different rules.
86 xattr_permission(struct inode *inode, const char *name, int mask)
89 * We can never set or remove an extended attribute on a read-only
90 * filesystem or on an immutable / append-only inode.
92 if (mask & MAY_WRITE) {
93 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
96 * Updating an xattr will likely cause i_uid and i_gid
97 * to be writen back improperly if their true value is
100 if (HAS_UNMAPPED_ID(inode))
105 * No restriction for security.* and system.* from the VFS. Decision
106 * on these is left to the underlying filesystem / security module.
108 if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
109 !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
113 * The trusted.* namespace can only be accessed by privileged users.
115 if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
116 if (!capable(CAP_SYS_ADMIN))
117 return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
122 * In the user.* namespace, only regular files and directories can have
123 * extended attributes. For sticky directories, only the owner and
124 * privileged users can write attributes.
126 if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
127 if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
128 return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
129 if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
130 (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
134 return inode_permission(inode, mask);
138 __vfs_setxattr(struct dentry *dentry, struct inode *inode, const char *name,
139 const void *value, size_t size, int flags)
141 const struct xattr_handler *handler;
143 handler = xattr_resolve_name(inode, &name);
145 return PTR_ERR(handler);
149 value = ""; /* empty EA, do not remove */
150 return handler->set(handler, dentry, inode, name, value, size, flags);
152 EXPORT_SYMBOL(__vfs_setxattr);
155 * __vfs_setxattr_noperm - perform setxattr operation without performing
158 * @dentry - object to perform setxattr on
159 * @name - xattr name to set
160 * @value - value to set @name to
161 * @size - size of @value
162 * @flags - flags to pass into filesystem operations
164 * returns the result of the internal setxattr or setsecurity operations.
166 * This function requires the caller to lock the inode's i_mutex before it
167 * is executed. It also assumes that the caller will make the appropriate
170 int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
171 const void *value, size_t size, int flags)
173 struct inode *inode = dentry->d_inode;
175 int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
176 XATTR_SECURITY_PREFIX_LEN);
179 inode->i_flags &= ~S_NOSEC;
180 if (inode->i_opflags & IOP_XATTR) {
181 error = __vfs_setxattr(dentry, inode, name, value, size, flags);
183 fsnotify_xattr(dentry);
184 security_inode_post_setxattr(dentry, name, value,
188 if (unlikely(is_bad_inode(inode)))
191 if (error == -EAGAIN) {
195 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
197 error = security_inode_setsecurity(inode, suffix, value,
200 fsnotify_xattr(dentry);
209 vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
210 size_t size, int flags)
212 struct inode *inode = dentry->d_inode;
215 error = xattr_permission(inode, name, MAY_WRITE);
220 error = security_inode_setxattr(dentry, name, value, size, flags);
224 error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
230 EXPORT_SYMBOL_GPL(vfs_setxattr);
233 xattr_getsecurity(struct inode *inode, const char *name, void *value,
239 if (!value || !size) {
240 len = security_inode_getsecurity(inode, name, &buffer, false);
244 len = security_inode_getsecurity(inode, name, &buffer, true);
251 memcpy(value, buffer, len);
253 security_release_secctx(buffer, len);
257 EXPORT_SYMBOL_GPL(xattr_getsecurity);
260 * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
262 * Allocate memory, if not already allocated, or re-allocate correct size,
263 * before retrieving the extended attribute.
265 * Returns the result of alloc, if failed, or the getxattr operation.
268 vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
269 size_t xattr_size, gfp_t flags)
271 const struct xattr_handler *handler;
272 struct inode *inode = dentry->d_inode;
273 char *value = *xattr_value;
276 error = xattr_permission(inode, name, MAY_READ);
280 handler = xattr_resolve_name(inode, &name);
282 return PTR_ERR(handler);
285 error = handler->get(handler, dentry, inode, name, NULL, 0);
289 if (!value || (error > xattr_size)) {
290 value = krealloc(*xattr_value, error + 1, flags);
293 memset(value, 0, error + 1);
296 error = handler->get(handler, dentry, inode, name, value, error);
297 *xattr_value = value;
302 __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
303 void *value, size_t size)
305 const struct xattr_handler *handler;
307 handler = xattr_resolve_name(inode, &name);
309 return PTR_ERR(handler);
312 return handler->get(handler, dentry, inode, name, value, size);
314 EXPORT_SYMBOL(__vfs_getxattr);
317 vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
319 struct inode *inode = dentry->d_inode;
322 error = xattr_permission(inode, name, MAY_READ);
326 error = security_inode_getxattr(dentry, name);
330 if (!strncmp(name, XATTR_SECURITY_PREFIX,
331 XATTR_SECURITY_PREFIX_LEN)) {
332 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
333 int ret = xattr_getsecurity(inode, suffix, value, size);
335 * Only overwrite the return value if a security module
336 * is actually active.
338 if (ret == -EOPNOTSUPP)
343 return __vfs_getxattr(dentry, inode, name, value, size);
345 EXPORT_SYMBOL_GPL(vfs_getxattr);
348 vfs_listxattr(struct dentry *dentry, char *list, size_t size)
350 struct inode *inode = d_inode(dentry);
353 error = security_inode_listxattr(dentry);
356 if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
358 error = inode->i_op->listxattr(dentry, list, size);
360 error = security_inode_listsecurity(inode, list, size);
361 if (size && error > size)
366 EXPORT_SYMBOL_GPL(vfs_listxattr);
369 __vfs_removexattr(struct dentry *dentry, const char *name)
371 struct inode *inode = d_inode(dentry);
372 const struct xattr_handler *handler;
374 handler = xattr_resolve_name(inode, &name);
376 return PTR_ERR(handler);
379 return handler->set(handler, dentry, inode, name, NULL, 0, XATTR_REPLACE);
381 EXPORT_SYMBOL(__vfs_removexattr);
384 vfs_removexattr(struct dentry *dentry, const char *name)
386 struct inode *inode = dentry->d_inode;
389 error = xattr_permission(inode, name, MAY_WRITE);
394 error = security_inode_removexattr(dentry, name);
398 error = __vfs_removexattr(dentry, name);
401 fsnotify_xattr(dentry);
402 evm_inode_post_removexattr(dentry, name);
409 EXPORT_SYMBOL_GPL(vfs_removexattr);
413 * Extended attribute SET operations
416 setxattr(struct dentry *d, const char __user *name, const void __user *value,
417 size_t size, int flags)
421 char kname[XATTR_NAME_MAX + 1];
423 if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
426 error = strncpy_from_user(kname, name, sizeof(kname));
427 if (error == 0 || error == sizeof(kname))
433 if (size > XATTR_SIZE_MAX)
435 kvalue = kvmalloc(size, GFP_KERNEL);
438 if (copy_from_user(kvalue, value, size)) {
442 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
443 (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
444 posix_acl_fix_xattr_from_user(kvalue, size);
447 error = vfs_setxattr(d, kname, kvalue, size, flags);
454 static int path_setxattr(const char __user *pathname,
455 const char __user *name, const void __user *value,
456 size_t size, int flags, unsigned int lookup_flags)
461 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
464 error = mnt_want_write(path.mnt);
466 error = setxattr(path.dentry, name, value, size, flags);
467 mnt_drop_write(path.mnt);
470 if (retry_estale(error, lookup_flags)) {
471 lookup_flags |= LOOKUP_REVAL;
477 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
478 const char __user *, name, const void __user *, value,
479 size_t, size, int, flags)
481 return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
484 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
485 const char __user *, name, const void __user *, value,
486 size_t, size, int, flags)
488 return path_setxattr(pathname, name, value, size, flags, 0);
491 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
492 const void __user *,value, size_t, size, int, flags)
494 struct fd f = fdget(fd);
500 error = mnt_want_write_file_path(f.file);
502 error = setxattr(f.file->f_path.dentry, name, value, size, flags);
503 mnt_drop_write_file_path(f.file);
510 * Extended attribute GET operations
513 getxattr(struct dentry *d, const char __user *name, void __user *value,
518 char kname[XATTR_NAME_MAX + 1];
520 error = strncpy_from_user(kname, name, sizeof(kname));
521 if (error == 0 || error == sizeof(kname))
527 if (size > XATTR_SIZE_MAX)
528 size = XATTR_SIZE_MAX;
529 kvalue = kvzalloc(size, GFP_KERNEL);
534 error = vfs_getxattr(d, kname, kvalue, size);
536 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
537 (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
538 posix_acl_fix_xattr_to_user(kvalue, size);
539 if (size && copy_to_user(value, kvalue, error))
541 } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
542 /* The file system tried to returned a value bigger
543 than XATTR_SIZE_MAX bytes. Not possible. */
552 static ssize_t path_getxattr(const char __user *pathname,
553 const char __user *name, void __user *value,
554 size_t size, unsigned int lookup_flags)
559 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
562 error = getxattr(path.dentry, name, value, size);
564 if (retry_estale(error, lookup_flags)) {
565 lookup_flags |= LOOKUP_REVAL;
571 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
572 const char __user *, name, void __user *, value, size_t, size)
574 return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
577 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
578 const char __user *, name, void __user *, value, size_t, size)
580 return path_getxattr(pathname, name, value, size, 0);
583 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
584 void __user *, value, size_t, size)
586 struct fd f = fdget(fd);
587 ssize_t error = -EBADF;
592 error = getxattr(f.file->f_path.dentry, name, value, size);
598 * Extended attribute LIST operations
601 listxattr(struct dentry *d, char __user *list, size_t size)
607 if (size > XATTR_LIST_MAX)
608 size = XATTR_LIST_MAX;
609 klist = kvmalloc(size, GFP_KERNEL);
614 error = vfs_listxattr(d, klist, size);
616 if (size && copy_to_user(list, klist, error))
618 } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
619 /* The file system tried to returned a list bigger
620 than XATTR_LIST_MAX bytes. Not possible. */
629 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
630 size_t size, unsigned int lookup_flags)
635 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
638 error = listxattr(path.dentry, list, size);
640 if (retry_estale(error, lookup_flags)) {
641 lookup_flags |= LOOKUP_REVAL;
647 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
650 return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
653 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
656 return path_listxattr(pathname, list, size, 0);
659 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
661 struct fd f = fdget(fd);
662 ssize_t error = -EBADF;
667 error = listxattr(f.file->f_path.dentry, list, size);
673 * Extended attribute REMOVE operations
676 removexattr(struct dentry *d, const char __user *name)
679 char kname[XATTR_NAME_MAX + 1];
681 error = strncpy_from_user(kname, name, sizeof(kname));
682 if (error == 0 || error == sizeof(kname))
687 return vfs_removexattr(d, kname);
690 static int path_removexattr(const char __user *pathname,
691 const char __user *name, unsigned int lookup_flags)
696 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
699 error = mnt_want_write(path.mnt);
701 error = removexattr(path.dentry, name);
702 mnt_drop_write(path.mnt);
705 if (retry_estale(error, lookup_flags)) {
706 lookup_flags |= LOOKUP_REVAL;
712 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
713 const char __user *, name)
715 return path_removexattr(pathname, name, LOOKUP_FOLLOW);
718 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
719 const char __user *, name)
721 return path_removexattr(pathname, name, 0);
724 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
726 struct fd f = fdget(fd);
732 error = mnt_want_write_file_path(f.file);
734 error = removexattr(f.file->f_path.dentry, name);
735 mnt_drop_write_file_path(f.file);
742 * Combine the results of the list() operation from every xattr_handler in the
746 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
748 const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
749 unsigned int size = 0;
752 for_each_xattr_handler(handlers, handler) {
753 if (!handler->name ||
754 (handler->list && !handler->list(dentry)))
756 size += strlen(handler->name) + 1;
762 for_each_xattr_handler(handlers, handler) {
763 if (!handler->name ||
764 (handler->list && !handler->list(dentry)))
766 len = strlen(handler->name);
767 if (len + 1 > buffer_size)
769 memcpy(buf, handler->name, len + 1);
771 buffer_size -= len + 1;
777 EXPORT_SYMBOL(generic_listxattr);
780 * xattr_full_name - Compute full attribute name from suffix
782 * @handler: handler of the xattr_handler operation
783 * @name: name passed to the xattr_handler operation
785 * The get and set xattr handler operations are called with the remainder of
786 * the attribute name after skipping the handler's prefix: for example, "foo"
787 * is passed to the get operation of a handler with prefix "user." to get
788 * attribute "user.foo". The full name is still "there" in the name though.
790 * Note: the list xattr handler operation when called from the vfs is passed a
791 * NULL name; some file systems use this operation internally, with varying
794 const char *xattr_full_name(const struct xattr_handler *handler,
797 size_t prefix_len = strlen(xattr_prefix(handler));
799 return name - prefix_len;
801 EXPORT_SYMBOL(xattr_full_name);
804 * Allocate new xattr and copy in the value; but leave the name to callers.
806 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
808 struct simple_xattr *new_xattr;
812 len = sizeof(*new_xattr) + size;
813 if (len < sizeof(*new_xattr))
816 new_xattr = kmalloc(len, GFP_KERNEL);
820 new_xattr->size = size;
821 memcpy(new_xattr->value, value, size);
826 * xattr GET operation for in-memory/pseudo filesystems
828 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
829 void *buffer, size_t size)
831 struct simple_xattr *xattr;
834 spin_lock(&xattrs->lock);
835 list_for_each_entry(xattr, &xattrs->head, list) {
836 if (strcmp(name, xattr->name))
841 if (size < xattr->size)
844 memcpy(buffer, xattr->value, xattr->size);
848 spin_unlock(&xattrs->lock);
853 * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
854 * @xattrs: target simple_xattr list
855 * @name: name of the extended attribute
856 * @value: value of the xattr. If %NULL, will remove the attribute.
857 * @size: size of the new xattr
858 * @flags: %XATTR_{CREATE|REPLACE}
860 * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
861 * with -EEXIST. If %XATTR_REPLACE is set, the xattr should exist;
862 * otherwise, fails with -ENODATA.
864 * Returns 0 on success, -errno on failure.
866 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);
917 static bool xattr_is_trusted(const char *name)
919 return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
922 static int xattr_list_one(char **buffer, ssize_t *remaining_size,
925 size_t len = strlen(name) + 1;
927 if (*remaining_size < len)
929 memcpy(*buffer, name, len);
932 *remaining_size -= len;
937 * xattr LIST operation for in-memory/pseudo filesystems
939 ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
940 char *buffer, size_t size)
942 bool trusted = capable(CAP_SYS_ADMIN);
943 struct simple_xattr *xattr;
944 ssize_t remaining_size = size;
947 #ifdef CONFIG_FS_POSIX_ACL
949 err = xattr_list_one(&buffer, &remaining_size,
950 XATTR_NAME_POSIX_ACL_ACCESS);
954 if (inode->i_default_acl) {
955 err = xattr_list_one(&buffer, &remaining_size,
956 XATTR_NAME_POSIX_ACL_DEFAULT);
962 spin_lock(&xattrs->lock);
963 list_for_each_entry(xattr, &xattrs->head, list) {
964 /* skip "trusted." attributes for unprivileged callers */
965 if (!trusted && xattr_is_trusted(xattr->name))
968 err = xattr_list_one(&buffer, &remaining_size, xattr->name);
972 spin_unlock(&xattrs->lock);
974 return err ? err : size - remaining_size;
978 * Adds an extended attribute to the list
980 void simple_xattr_list_add(struct simple_xattrs *xattrs,
981 struct simple_xattr *new_xattr)
983 spin_lock(&xattrs->lock);
984 list_add(&new_xattr->list, &xattrs->head);
985 spin_unlock(&xattrs->lock);