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);