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 vfs_getxattr(struct dentry *dentry, char *name, void *value, size_t size)
110 struct inode *inode = dentry->d_inode;
113 error = xattr_permission(inode, name, MAY_READ);
117 error = security_inode_getxattr(dentry, name);
121 if (inode->i_op->getxattr)
122 error = inode->i_op->getxattr(dentry, name, value, size);
126 if (!strncmp(name, XATTR_SECURITY_PREFIX,
127 XATTR_SECURITY_PREFIX_LEN)) {
128 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
129 int ret = security_inode_getsecurity(inode, suffix, value,
132 * Only overwrite the return value if a security module
133 * is actually active.
135 if (ret != -EOPNOTSUPP)
141 EXPORT_SYMBOL_GPL(vfs_getxattr);
144 vfs_listxattr(struct dentry *d, char *list, size_t size)
148 error = security_inode_listxattr(d);
152 if (d->d_inode->i_op && d->d_inode->i_op->listxattr) {
153 error = d->d_inode->i_op->listxattr(d, list, size);
155 error = security_inode_listsecurity(d->d_inode, list, size);
156 if (size && error > size)
161 EXPORT_SYMBOL_GPL(vfs_listxattr);
164 vfs_removexattr(struct dentry *dentry, char *name)
166 struct inode *inode = dentry->d_inode;
169 if (!inode->i_op->removexattr)
172 error = xattr_permission(inode, name, MAY_WRITE);
176 error = security_inode_removexattr(dentry, name);
180 mutex_lock(&inode->i_mutex);
181 error = inode->i_op->removexattr(dentry, name);
182 mutex_unlock(&inode->i_mutex);
185 fsnotify_xattr(dentry);
188 EXPORT_SYMBOL_GPL(vfs_removexattr);
192 * Extended attribute SET operations
195 setxattr(struct dentry *d, char __user *name, void __user *value,
196 size_t size, int flags)
200 char kname[XATTR_NAME_MAX + 1];
202 if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
205 error = strncpy_from_user(kname, name, sizeof(kname));
206 if (error == 0 || error == sizeof(kname))
212 if (size > XATTR_SIZE_MAX)
214 kvalue = kmalloc(size, GFP_KERNEL);
217 if (copy_from_user(kvalue, value, size)) {
223 error = vfs_setxattr(d, kname, kvalue, size, flags);
229 sys_setxattr(char __user *path, char __user *name, void __user *value,
230 size_t size, int flags)
235 error = user_path_walk(path, &nd);
238 error = setxattr(nd.dentry, name, value, size, flags);
244 sys_lsetxattr(char __user *path, char __user *name, void __user *value,
245 size_t size, int flags)
250 error = user_path_walk_link(path, &nd);
253 error = setxattr(nd.dentry, name, value, size, flags);
259 sys_fsetxattr(int fd, char __user *name, void __user *value,
260 size_t size, int flags)
263 struct dentry *dentry;
269 dentry = f->f_path.dentry;
270 audit_inode(NULL, dentry->d_inode);
271 error = setxattr(dentry, name, value, size, flags);
277 * Extended attribute GET operations
280 getxattr(struct dentry *d, char __user *name, void __user *value, size_t size)
284 char kname[XATTR_NAME_MAX + 1];
286 error = strncpy_from_user(kname, name, sizeof(kname));
287 if (error == 0 || error == sizeof(kname))
293 if (size > XATTR_SIZE_MAX)
294 size = XATTR_SIZE_MAX;
295 kvalue = kzalloc(size, GFP_KERNEL);
300 error = vfs_getxattr(d, kname, kvalue, size);
302 if (size && copy_to_user(value, kvalue, error))
304 } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
305 /* The file system tried to returned a value bigger
306 than XATTR_SIZE_MAX bytes. Not possible. */
314 sys_getxattr(char __user *path, char __user *name, void __user *value,
320 error = user_path_walk(path, &nd);
323 error = getxattr(nd.dentry, name, value, size);
329 sys_lgetxattr(char __user *path, char __user *name, void __user *value,
335 error = user_path_walk_link(path, &nd);
338 error = getxattr(nd.dentry, name, value, size);
344 sys_fgetxattr(int fd, char __user *name, void __user *value, size_t size)
347 ssize_t error = -EBADF;
352 audit_inode(NULL, f->f_path.dentry->d_inode);
353 error = getxattr(f->f_path.dentry, name, value, size);
359 * Extended attribute LIST operations
362 listxattr(struct dentry *d, char __user *list, size_t size)
368 if (size > XATTR_LIST_MAX)
369 size = XATTR_LIST_MAX;
370 klist = kmalloc(size, GFP_KERNEL);
375 error = vfs_listxattr(d, klist, size);
377 if (size && copy_to_user(list, klist, error))
379 } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
380 /* The file system tried to returned a list bigger
381 than XATTR_LIST_MAX bytes. Not possible. */
389 sys_listxattr(char __user *path, char __user *list, size_t size)
394 error = user_path_walk(path, &nd);
397 error = listxattr(nd.dentry, list, size);
403 sys_llistxattr(char __user *path, char __user *list, size_t size)
408 error = user_path_walk_link(path, &nd);
411 error = listxattr(nd.dentry, list, size);
417 sys_flistxattr(int fd, char __user *list, size_t size)
420 ssize_t error = -EBADF;
425 audit_inode(NULL, f->f_path.dentry->d_inode);
426 error = listxattr(f->f_path.dentry, list, size);
432 * Extended attribute REMOVE operations
435 removexattr(struct dentry *d, char __user *name)
438 char kname[XATTR_NAME_MAX + 1];
440 error = strncpy_from_user(kname, name, sizeof(kname));
441 if (error == 0 || error == sizeof(kname))
446 return vfs_removexattr(d, kname);
450 sys_removexattr(char __user *path, char __user *name)
455 error = user_path_walk(path, &nd);
458 error = removexattr(nd.dentry, name);
464 sys_lremovexattr(char __user *path, char __user *name)
469 error = user_path_walk_link(path, &nd);
472 error = removexattr(nd.dentry, name);
478 sys_fremovexattr(int fd, char __user *name)
481 struct dentry *dentry;
487 dentry = f->f_path.dentry;
488 audit_inode(NULL, dentry->d_inode);
489 error = removexattr(dentry, name);
496 strcmp_prefix(const char *a, const char *a_prefix)
498 while (*a_prefix && *a == *a_prefix) {
502 return *a_prefix ? NULL : a;
506 * In order to implement different sets of xattr operations for each xattr
507 * prefix with the generic xattr API, a filesystem should create a
508 * null-terminated array of struct xattr_handler (one for each prefix) and
509 * hang a pointer to it off of the s_xattr field of the superblock.
511 * The generic_fooxattr() functions will use this list to dispatch xattr
512 * operations to the correct xattr_handler.
514 #define for_each_xattr_handler(handlers, handler) \
515 for ((handler) = *(handlers)++; \
517 (handler) = *(handlers)++)
520 * Find the xattr_handler with the matching prefix.
522 static struct xattr_handler *
523 xattr_resolve_name(struct xattr_handler **handlers, const char **name)
525 struct xattr_handler *handler;
530 for_each_xattr_handler(handlers, handler) {
531 const char *n = strcmp_prefix(*name, handler->prefix);
541 * Find the handler for the prefix and dispatch its get() operation.
544 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
546 struct xattr_handler *handler;
547 struct inode *inode = dentry->d_inode;
549 handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
552 return handler->get(inode, name, buffer, size);
556 * Combine the results of the list() operation from every xattr_handler in the
560 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
562 struct inode *inode = dentry->d_inode;
563 struct xattr_handler *handler, **handlers = inode->i_sb->s_xattr;
564 unsigned int size = 0;
567 for_each_xattr_handler(handlers, handler)
568 size += handler->list(inode, NULL, 0, NULL, 0);
572 for_each_xattr_handler(handlers, handler) {
573 size = handler->list(inode, buf, buffer_size, NULL, 0);
574 if (size > buffer_size)
585 * Find the handler for the prefix and dispatch its set() operation.
588 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
590 struct xattr_handler *handler;
591 struct inode *inode = dentry->d_inode;
594 value = ""; /* empty EA, do not remove */
595 handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
598 return handler->set(inode, name, value, size, flags);
602 * Find the handler for the prefix and dispatch its set() operation to remove
603 * any associated extended attribute.
606 generic_removexattr(struct dentry *dentry, const char *name)
608 struct xattr_handler *handler;
609 struct inode *inode = dentry->d_inode;
611 handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
614 return handler->set(inode, name, NULL, 0, XATTR_REPLACE);
617 EXPORT_SYMBOL(generic_getxattr);
618 EXPORT_SYMBOL(generic_listxattr);
619 EXPORT_SYMBOL(generic_setxattr);
620 EXPORT_SYMBOL(generic_removexattr);