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/smp_lock.h>
13 #include <linux/file.h>
14 #include <linux/xattr.h>
15 #include <linux/namei.h>
16 #include <linux/security.h>
17 #include <linux/syscalls.h>
18 #include <linux/module.h>
19 #include <linux/fsnotify.h>
20 #include <linux/audit.h>
21 #include <linux/mount.h>
22 #include <asm/uaccess.h>
26 * Check permissions for extended attribute access. This is a bit complicated
27 * because different namespaces have very different rules.
30 xattr_permission(struct inode *inode, const char *name, int mask)
33 * We can never set or remove an extended attribute on a read-only
34 * filesystem or on an immutable / append-only inode.
36 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 accessed by a privilegued user.
54 if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
55 return (capable(CAP_SYS_ADMIN) ? 0 : -EPERM);
57 if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
58 if (!S_ISREG(inode->i_mode) &&
59 (!S_ISDIR(inode->i_mode) || inode->i_mode & S_ISVTX))
63 return permission(inode, mask, NULL);
67 vfs_setxattr(struct dentry *dentry, char *name, void *value,
68 size_t size, int flags)
70 struct inode *inode = dentry->d_inode;
73 error = xattr_permission(inode, name, MAY_WRITE);
77 mutex_lock(&inode->i_mutex);
78 error = security_inode_setxattr(dentry, name, value, size, flags);
82 if (inode->i_op->setxattr) {
83 error = inode->i_op->setxattr(dentry, name, value, size, flags);
85 fsnotify_xattr(dentry);
86 security_inode_post_setxattr(dentry, name, value,
89 } else if (!strncmp(name, XATTR_SECURITY_PREFIX,
90 XATTR_SECURITY_PREFIX_LEN)) {
91 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
92 error = security_inode_setsecurity(inode, suffix, value,
95 fsnotify_xattr(dentry);
98 mutex_unlock(&inode->i_mutex);
101 EXPORT_SYMBOL_GPL(vfs_setxattr);
104 vfs_getxattr(struct dentry *dentry, char *name, void *value, size_t size)
106 struct inode *inode = dentry->d_inode;
109 error = xattr_permission(inode, name, MAY_READ);
113 error = security_inode_getxattr(dentry, name);
117 if (inode->i_op->getxattr)
118 error = inode->i_op->getxattr(dentry, name, value, size);
122 if (!strncmp(name, XATTR_SECURITY_PREFIX,
123 XATTR_SECURITY_PREFIX_LEN)) {
124 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
125 int ret = security_inode_getsecurity(inode, suffix, value,
128 * Only overwrite the return value if a security module
129 * is actually active.
131 if (ret != -EOPNOTSUPP)
137 EXPORT_SYMBOL_GPL(vfs_getxattr);
140 vfs_removexattr(struct dentry *dentry, char *name)
142 struct inode *inode = dentry->d_inode;
145 if (!inode->i_op->removexattr)
148 error = xattr_permission(inode, name, MAY_WRITE);
152 error = security_inode_removexattr(dentry, name);
156 mutex_lock(&inode->i_mutex);
157 error = inode->i_op->removexattr(dentry, name);
158 mutex_unlock(&inode->i_mutex);
161 fsnotify_xattr(dentry);
164 EXPORT_SYMBOL_GPL(vfs_removexattr);
168 * Extended attribute SET operations
171 setxattr(struct dentry *d, char __user *name, void __user *value,
172 size_t size, int flags, struct vfsmount *mnt)
176 char kname[XATTR_NAME_MAX + 1];
178 if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
181 error = strncpy_from_user(kname, name, sizeof(kname));
182 if (error == 0 || error == sizeof(kname))
188 if (size > XATTR_SIZE_MAX)
190 kvalue = kmalloc(size, GFP_KERNEL);
193 if (copy_from_user(kvalue, value, size)) {
199 if (MNT_IS_RDONLY(mnt))
202 error = vfs_setxattr(d, kname, kvalue, size, flags);
208 sys_setxattr(char __user *path, char __user *name, void __user *value,
209 size_t size, int flags)
214 error = user_path_walk(path, &nd);
217 error = setxattr(nd.dentry, name, value, size, flags, nd.mnt);
223 sys_lsetxattr(char __user *path, char __user *name, void __user *value,
224 size_t size, int flags)
229 error = user_path_walk_link(path, &nd);
232 error = setxattr(nd.dentry, name, value, size, flags, nd.mnt);
238 sys_fsetxattr(int fd, char __user *name, void __user *value,
239 size_t size, int flags)
242 struct dentry *dentry;
248 dentry = f->f_dentry;
249 audit_inode(NULL, dentry->d_inode, 0);
250 error = setxattr(dentry, name, value, size, flags, f->f_vfsmnt);
256 * Extended attribute GET operations
259 getxattr(struct dentry *d, char __user *name, void __user *value, size_t size)
263 char kname[XATTR_NAME_MAX + 1];
265 error = strncpy_from_user(kname, name, sizeof(kname));
266 if (error == 0 || error == sizeof(kname))
272 if (size > XATTR_SIZE_MAX)
273 size = XATTR_SIZE_MAX;
274 kvalue = kzalloc(size, GFP_KERNEL);
279 error = vfs_getxattr(d, kname, kvalue, size);
281 if (size && copy_to_user(value, kvalue, error))
283 } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
284 /* The file system tried to returned a value bigger
285 than XATTR_SIZE_MAX bytes. Not possible. */
293 sys_getxattr(char __user *path, char __user *name, void __user *value,
299 error = user_path_walk(path, &nd);
302 error = getxattr(nd.dentry, name, value, size);
308 sys_lgetxattr(char __user *path, char __user *name, void __user *value,
314 error = user_path_walk_link(path, &nd);
317 error = getxattr(nd.dentry, name, value, size);
323 sys_fgetxattr(int fd, char __user *name, void __user *value, size_t size)
326 ssize_t error = -EBADF;
331 error = getxattr(f->f_dentry, name, value, size);
337 * Extended attribute LIST operations
340 listxattr(struct dentry *d, char __user *list, size_t size)
346 if (size > XATTR_LIST_MAX)
347 size = XATTR_LIST_MAX;
348 klist = kmalloc(size, GFP_KERNEL);
353 error = security_inode_listxattr(d);
357 if (d->d_inode->i_op && d->d_inode->i_op->listxattr) {
358 error = d->d_inode->i_op->listxattr(d, klist, size);
360 error = security_inode_listsecurity(d->d_inode, klist, size);
361 if (size && error > size)
365 if (size && copy_to_user(list, klist, error))
367 } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
368 /* The file system tried to returned a list bigger
369 than XATTR_LIST_MAX bytes. Not possible. */
378 sys_listxattr(char __user *path, char __user *list, size_t size)
383 error = user_path_walk(path, &nd);
386 error = listxattr(nd.dentry, list, size);
392 sys_llistxattr(char __user *path, char __user *list, size_t size)
397 error = user_path_walk_link(path, &nd);
400 error = listxattr(nd.dentry, list, size);
406 sys_flistxattr(int fd, char __user *list, size_t size)
409 ssize_t error = -EBADF;
414 error = listxattr(f->f_dentry, list, size);
420 * Extended attribute REMOVE operations
423 removexattr(struct dentry *d, char __user *name, struct vfsmount *mnt)
426 char kname[XATTR_NAME_MAX + 1];
428 error = strncpy_from_user(kname, name, sizeof(kname));
429 if (error == 0 || error == sizeof(kname))
434 if (MNT_IS_RDONLY(mnt))
437 return vfs_removexattr(d, kname);
441 sys_removexattr(char __user *path, char __user *name)
446 error = user_path_walk(path, &nd);
449 error = removexattr(nd.dentry, name, nd.mnt);
455 sys_lremovexattr(char __user *path, char __user *name)
460 error = user_path_walk_link(path, &nd);
463 error = removexattr(nd.dentry, name, nd.mnt);
469 sys_fremovexattr(int fd, char __user *name)
472 struct dentry *dentry;
478 dentry = f->f_dentry;
479 audit_inode(NULL, dentry->d_inode, 0);
480 error = removexattr(dentry, name, f->f_vfsmnt);
487 strcmp_prefix(const char *a, const char *a_prefix)
489 while (*a_prefix && *a == *a_prefix) {
493 return *a_prefix ? NULL : a;
497 * In order to implement different sets of xattr operations for each xattr
498 * prefix with the generic xattr API, a filesystem should create a
499 * null-terminated array of struct xattr_handler (one for each prefix) and
500 * hang a pointer to it off of the s_xattr field of the superblock.
502 * The generic_fooxattr() functions will use this list to dispatch xattr
503 * operations to the correct xattr_handler.
505 #define for_each_xattr_handler(handlers, handler) \
506 for ((handler) = *(handlers)++; \
508 (handler) = *(handlers)++)
511 * Find the xattr_handler with the matching prefix.
513 static struct xattr_handler *
514 xattr_resolve_name(struct xattr_handler **handlers, const char **name)
516 struct xattr_handler *handler;
521 for_each_xattr_handler(handlers, handler) {
522 const char *n = strcmp_prefix(*name, handler->prefix);
532 * Find the handler for the prefix and dispatch its get() operation.
535 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
537 struct xattr_handler *handler;
538 struct inode *inode = dentry->d_inode;
540 handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
543 return handler->get(inode, name, buffer, size);
547 * Combine the results of the list() operation from every xattr_handler in the
551 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
553 struct inode *inode = dentry->d_inode;
554 struct xattr_handler *handler, **handlers = inode->i_sb->s_xattr;
555 unsigned int size = 0;
558 for_each_xattr_handler(handlers, handler)
559 size += handler->list(inode, NULL, 0, NULL, 0);
563 for_each_xattr_handler(handlers, handler) {
564 size = handler->list(inode, buf, buffer_size, NULL, 0);
565 if (size > buffer_size)
576 * Find the handler for the prefix and dispatch its set() operation.
579 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
581 struct xattr_handler *handler;
582 struct inode *inode = dentry->d_inode;
585 value = ""; /* empty EA, do not remove */
586 handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
589 return handler->set(inode, name, value, size, flags);
593 * Find the handler for the prefix and dispatch its set() operation to remove
594 * any associated extended attribute.
597 generic_removexattr(struct dentry *dentry, const char *name)
599 struct xattr_handler *handler;
600 struct inode *inode = dentry->d_inode;
602 handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
605 return handler->set(inode, name, NULL, 0, XATTR_REPLACE);
608 EXPORT_SYMBOL(generic_getxattr);
609 EXPORT_SYMBOL(generic_listxattr);
610 EXPORT_SYMBOL(generic_setxattr);
611 EXPORT_SYMBOL(generic_removexattr);