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/namei.h>
15 #include <linux/security.h>
16 #include <linux/syscalls.h>
17 #include <linux/module.h>
18 #include <linux/fsnotify.h>
19 #include <linux/audit.h>
20 #include <asm/uaccess.h>
24 * Check permissions for extended attribute access. This is a bit complicated
25 * because different namespaces have very different rules.
28 xattr_permission(struct inode *inode, const char *name, int mask)
31 * We can never set or remove an extended attribute on a read-only
32 * filesystem or on an immutable / append-only inode.
34 if (mask & MAY_WRITE) {
37 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
42 * No restriction for security.* and system.* from the VFS. Decision
43 * on these is left to the underlying filesystem / security module.
45 if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
46 !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
50 * The trusted.* namespace can only be accessed by a privileged user.
52 if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
53 return (capable(CAP_SYS_ADMIN) ? 0 : -EPERM);
55 /* In user.* namespace, only regular files and directories can have
56 * extended attributes. For sticky directories, only the owner and
57 * privileged user can write attributes.
59 if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
60 if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
62 if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
63 (mask & MAY_WRITE) && !is_owner_or_cap(inode))
67 return permission(inode, mask, NULL);
71 vfs_setxattr(struct dentry *dentry, char *name, void *value,
72 size_t size, int flags)
74 struct inode *inode = dentry->d_inode;
77 error = xattr_permission(inode, name, MAY_WRITE);
81 mutex_lock(&inode->i_mutex);
82 error = security_inode_setxattr(dentry, name, value, size, flags);
86 if (inode->i_op->setxattr) {
87 error = inode->i_op->setxattr(dentry, name, value, size, flags);
89 fsnotify_xattr(dentry);
90 security_inode_post_setxattr(dentry, name, value,
93 } else if (!strncmp(name, XATTR_SECURITY_PREFIX,
94 XATTR_SECURITY_PREFIX_LEN)) {
95 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
96 error = security_inode_setsecurity(inode, suffix, value,
99 fsnotify_xattr(dentry);
102 mutex_unlock(&inode->i_mutex);
105 EXPORT_SYMBOL_GPL(vfs_setxattr);
108 xattr_getsecurity(struct inode *inode, const char *name, void *value,
114 if (!value || !size) {
115 len = security_inode_getsecurity(inode, name, &buffer, false);
119 len = security_inode_getsecurity(inode, name, &buffer, true);
126 memcpy(value, buffer, len);
128 security_release_secctx(buffer, len);
132 EXPORT_SYMBOL_GPL(xattr_getsecurity);
135 vfs_getxattr(struct dentry *dentry, char *name, void *value, size_t size)
137 struct inode *inode = dentry->d_inode;
140 error = xattr_permission(inode, name, MAY_READ);
144 error = security_inode_getxattr(dentry, name);
148 if (inode->i_op->getxattr)
149 error = inode->i_op->getxattr(dentry, name, value, size);
153 if (!strncmp(name, XATTR_SECURITY_PREFIX,
154 XATTR_SECURITY_PREFIX_LEN)) {
155 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
156 int ret = xattr_getsecurity(inode, suffix, value, size);
158 * Only overwrite the return value if a security module
159 * is actually active.
161 if (ret != -EOPNOTSUPP)
167 EXPORT_SYMBOL_GPL(vfs_getxattr);
170 vfs_listxattr(struct dentry *d, char *list, size_t size)
174 error = security_inode_listxattr(d);
178 if (d->d_inode->i_op && d->d_inode->i_op->listxattr) {
179 error = d->d_inode->i_op->listxattr(d, list, size);
181 error = security_inode_listsecurity(d->d_inode, list, size);
182 if (size && error > size)
187 EXPORT_SYMBOL_GPL(vfs_listxattr);
190 vfs_removexattr(struct dentry *dentry, char *name)
192 struct inode *inode = dentry->d_inode;
195 if (!inode->i_op->removexattr)
198 error = xattr_permission(inode, name, MAY_WRITE);
202 error = security_inode_removexattr(dentry, name);
206 mutex_lock(&inode->i_mutex);
207 error = inode->i_op->removexattr(dentry, name);
208 mutex_unlock(&inode->i_mutex);
211 fsnotify_xattr(dentry);
214 EXPORT_SYMBOL_GPL(vfs_removexattr);
218 * Extended attribute SET operations
221 setxattr(struct dentry *d, char __user *name, void __user *value,
222 size_t size, int flags)
226 char kname[XATTR_NAME_MAX + 1];
228 if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
231 error = strncpy_from_user(kname, name, sizeof(kname));
232 if (error == 0 || error == sizeof(kname))
238 if (size > XATTR_SIZE_MAX)
240 kvalue = kmalloc(size, GFP_KERNEL);
243 if (copy_from_user(kvalue, value, size)) {
249 error = vfs_setxattr(d, kname, kvalue, size, flags);
255 sys_setxattr(char __user *path, char __user *name, void __user *value,
256 size_t size, int flags)
261 error = user_path_walk(path, &nd);
264 error = setxattr(nd.dentry, name, value, size, flags);
270 sys_lsetxattr(char __user *path, char __user *name, void __user *value,
271 size_t size, int flags)
276 error = user_path_walk_link(path, &nd);
279 error = setxattr(nd.dentry, name, value, size, flags);
285 sys_fsetxattr(int fd, char __user *name, void __user *value,
286 size_t size, int flags)
289 struct dentry *dentry;
295 dentry = f->f_path.dentry;
296 audit_inode(NULL, dentry);
297 error = setxattr(dentry, name, value, size, flags);
303 * Extended attribute GET operations
306 getxattr(struct dentry *d, char __user *name, void __user *value, size_t size)
310 char kname[XATTR_NAME_MAX + 1];
312 error = strncpy_from_user(kname, name, sizeof(kname));
313 if (error == 0 || error == sizeof(kname))
319 if (size > XATTR_SIZE_MAX)
320 size = XATTR_SIZE_MAX;
321 kvalue = kzalloc(size, GFP_KERNEL);
326 error = vfs_getxattr(d, kname, kvalue, size);
328 if (size && copy_to_user(value, kvalue, error))
330 } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
331 /* The file system tried to returned a value bigger
332 than XATTR_SIZE_MAX bytes. Not possible. */
340 sys_getxattr(char __user *path, char __user *name, void __user *value,
346 error = user_path_walk(path, &nd);
349 error = getxattr(nd.dentry, name, value, size);
355 sys_lgetxattr(char __user *path, char __user *name, void __user *value,
361 error = user_path_walk_link(path, &nd);
364 error = getxattr(nd.dentry, name, value, size);
370 sys_fgetxattr(int fd, char __user *name, void __user *value, size_t size)
373 ssize_t error = -EBADF;
378 audit_inode(NULL, f->f_path.dentry);
379 error = getxattr(f->f_path.dentry, name, value, size);
385 * Extended attribute LIST operations
388 listxattr(struct dentry *d, char __user *list, size_t size)
394 if (size > XATTR_LIST_MAX)
395 size = XATTR_LIST_MAX;
396 klist = kmalloc(size, GFP_KERNEL);
401 error = vfs_listxattr(d, klist, size);
403 if (size && copy_to_user(list, klist, error))
405 } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
406 /* The file system tried to returned a list bigger
407 than XATTR_LIST_MAX bytes. Not possible. */
415 sys_listxattr(char __user *path, char __user *list, size_t size)
420 error = user_path_walk(path, &nd);
423 error = listxattr(nd.dentry, list, size);
429 sys_llistxattr(char __user *path, char __user *list, size_t size)
434 error = user_path_walk_link(path, &nd);
437 error = listxattr(nd.dentry, list, size);
443 sys_flistxattr(int fd, char __user *list, size_t size)
446 ssize_t error = -EBADF;
451 audit_inode(NULL, f->f_path.dentry);
452 error = listxattr(f->f_path.dentry, list, size);
458 * Extended attribute REMOVE operations
461 removexattr(struct dentry *d, char __user *name)
464 char kname[XATTR_NAME_MAX + 1];
466 error = strncpy_from_user(kname, name, sizeof(kname));
467 if (error == 0 || error == sizeof(kname))
472 return vfs_removexattr(d, kname);
476 sys_removexattr(char __user *path, char __user *name)
481 error = user_path_walk(path, &nd);
484 error = removexattr(nd.dentry, name);
490 sys_lremovexattr(char __user *path, char __user *name)
495 error = user_path_walk_link(path, &nd);
498 error = removexattr(nd.dentry, name);
504 sys_fremovexattr(int fd, char __user *name)
507 struct dentry *dentry;
513 dentry = f->f_path.dentry;
514 audit_inode(NULL, dentry);
515 error = removexattr(dentry, name);
522 strcmp_prefix(const char *a, const char *a_prefix)
524 while (*a_prefix && *a == *a_prefix) {
528 return *a_prefix ? NULL : a;
532 * In order to implement different sets of xattr operations for each xattr
533 * prefix with the generic xattr API, a filesystem should create a
534 * null-terminated array of struct xattr_handler (one for each prefix) and
535 * hang a pointer to it off of the s_xattr field of the superblock.
537 * The generic_fooxattr() functions will use this list to dispatch xattr
538 * operations to the correct xattr_handler.
540 #define for_each_xattr_handler(handlers, handler) \
541 for ((handler) = *(handlers)++; \
543 (handler) = *(handlers)++)
546 * Find the xattr_handler with the matching prefix.
548 static struct xattr_handler *
549 xattr_resolve_name(struct xattr_handler **handlers, const char **name)
551 struct xattr_handler *handler;
556 for_each_xattr_handler(handlers, handler) {
557 const char *n = strcmp_prefix(*name, handler->prefix);
567 * Find the handler for the prefix and dispatch its get() operation.
570 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
572 struct xattr_handler *handler;
573 struct inode *inode = dentry->d_inode;
575 handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
578 return handler->get(inode, name, buffer, size);
582 * Combine the results of the list() operation from every xattr_handler in the
586 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
588 struct inode *inode = dentry->d_inode;
589 struct xattr_handler *handler, **handlers = inode->i_sb->s_xattr;
590 unsigned int size = 0;
593 for_each_xattr_handler(handlers, handler)
594 size += handler->list(inode, NULL, 0, NULL, 0);
598 for_each_xattr_handler(handlers, handler) {
599 size = handler->list(inode, buf, buffer_size, NULL, 0);
600 if (size > buffer_size)
611 * Find the handler for the prefix and dispatch its set() operation.
614 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
616 struct xattr_handler *handler;
617 struct inode *inode = dentry->d_inode;
620 value = ""; /* empty EA, do not remove */
621 handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
624 return handler->set(inode, name, value, size, flags);
628 * Find the handler for the prefix and dispatch its set() operation to remove
629 * any associated extended attribute.
632 generic_removexattr(struct dentry *dentry, const char *name)
634 struct xattr_handler *handler;
635 struct inode *inode = dentry->d_inode;
637 handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
640 return handler->set(inode, name, NULL, 0, XATTR_REPLACE);
643 EXPORT_SYMBOL(generic_getxattr);
644 EXPORT_SYMBOL(generic_listxattr);
645 EXPORT_SYMBOL(generic_setxattr);
646 EXPORT_SYMBOL(generic_removexattr);