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>
24 #include <asm/uaccess.h>
27 * Check permissions for extended attribute access. This is a bit complicated
28 * because different namespaces have very different rules.
31 xattr_permission(struct inode *inode, const char *name, int mask)
34 * We can never set or remove an extended attribute on a read-only
35 * filesystem or on an immutable / append-only inode.
37 if (mask & MAY_WRITE) {
38 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
43 * No restriction for security.* and system.* from the VFS. Decision
44 * on these is left to the underlying filesystem / security module.
46 if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
47 !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
51 * The trusted.* namespace can only be accessed by privileged users.
53 if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
54 if (!capable(CAP_SYS_ADMIN))
55 return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
60 * In the user.* namespace, only regular files and directories can have
61 * extended attributes. For sticky directories, only the owner and
62 * privileged users can write attributes.
64 if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
65 if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
66 return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
67 if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
68 (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
72 return inode_permission(inode, mask);
76 * __vfs_setxattr_noperm - perform setxattr operation without performing
79 * @dentry - object to perform setxattr on
80 * @name - xattr name to set
81 * @value - value to set @name to
82 * @size - size of @value
83 * @flags - flags to pass into filesystem operations
85 * returns the result of the internal setxattr or setsecurity operations.
87 * This function requires the caller to lock the inode's i_mutex before it
88 * is executed. It also assumes that the caller will make the appropriate
91 int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
92 const void *value, size_t size, int flags)
94 struct inode *inode = dentry->d_inode;
95 int error = -EOPNOTSUPP;
96 int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
97 XATTR_SECURITY_PREFIX_LEN);
100 inode->i_flags &= ~S_NOSEC;
101 if (inode->i_op->setxattr) {
102 error = inode->i_op->setxattr(dentry, name, value, size, flags);
104 fsnotify_xattr(dentry);
105 security_inode_post_setxattr(dentry, name, value,
109 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
110 error = security_inode_setsecurity(inode, suffix, value,
113 fsnotify_xattr(dentry);
121 vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
122 size_t size, int flags)
124 struct inode *inode = dentry->d_inode;
127 error = xattr_permission(inode, name, MAY_WRITE);
131 mutex_lock(&inode->i_mutex);
132 error = security_inode_setxattr(dentry, name, value, size, flags);
136 error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
139 mutex_unlock(&inode->i_mutex);
142 EXPORT_SYMBOL_GPL(vfs_setxattr);
145 xattr_getsecurity(struct inode *inode, const char *name, void *value,
151 if (!value || !size) {
152 len = security_inode_getsecurity(inode, name, &buffer, false);
156 len = security_inode_getsecurity(inode, name, &buffer, true);
163 memcpy(value, buffer, len);
165 security_release_secctx(buffer, len);
169 EXPORT_SYMBOL_GPL(xattr_getsecurity);
172 * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
174 * Allocate memory, if not already allocated, or re-allocate correct size,
175 * before retrieving the extended attribute.
177 * Returns the result of alloc, if failed, or the getxattr operation.
180 vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
181 size_t xattr_size, gfp_t flags)
183 struct inode *inode = dentry->d_inode;
184 char *value = *xattr_value;
187 error = xattr_permission(inode, name, MAY_READ);
191 if (!inode->i_op->getxattr)
194 error = inode->i_op->getxattr(dentry, name, NULL, 0);
198 if (!value || (error > xattr_size)) {
199 value = krealloc(*xattr_value, error + 1, flags);
202 memset(value, 0, error + 1);
205 error = inode->i_op->getxattr(dentry, name, value, error);
206 *xattr_value = value;
210 /* Compare an extended attribute value with the given value */
211 int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name,
212 const char *value, size_t size, gfp_t flags)
214 char *xattr_value = NULL;
217 rc = vfs_getxattr_alloc(dentry, xattr_name, &xattr_value, 0, flags);
221 if ((rc != size) || (memcmp(xattr_value, value, rc) != 0))
230 vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
232 struct inode *inode = dentry->d_inode;
235 error = xattr_permission(inode, name, MAY_READ);
239 error = security_inode_getxattr(dentry, name);
243 if (!strncmp(name, XATTR_SECURITY_PREFIX,
244 XATTR_SECURITY_PREFIX_LEN)) {
245 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
246 int ret = xattr_getsecurity(inode, suffix, value, size);
248 * Only overwrite the return value if a security module
249 * is actually active.
251 if (ret == -EOPNOTSUPP)
256 if (inode->i_op->getxattr)
257 error = inode->i_op->getxattr(dentry, name, value, size);
263 EXPORT_SYMBOL_GPL(vfs_getxattr);
266 vfs_listxattr(struct dentry *d, char *list, size_t size)
270 error = security_inode_listxattr(d);
274 if (d->d_inode->i_op->listxattr) {
275 error = d->d_inode->i_op->listxattr(d, list, size);
277 error = security_inode_listsecurity(d->d_inode, list, size);
278 if (size && error > size)
283 EXPORT_SYMBOL_GPL(vfs_listxattr);
286 vfs_removexattr(struct dentry *dentry, const char *name)
288 struct inode *inode = dentry->d_inode;
291 if (!inode->i_op->removexattr)
294 error = xattr_permission(inode, name, MAY_WRITE);
298 mutex_lock(&inode->i_mutex);
299 error = security_inode_removexattr(dentry, name);
301 mutex_unlock(&inode->i_mutex);
305 error = inode->i_op->removexattr(dentry, name);
306 mutex_unlock(&inode->i_mutex);
309 fsnotify_xattr(dentry);
310 evm_inode_post_removexattr(dentry, name);
314 EXPORT_SYMBOL_GPL(vfs_removexattr);
318 * Extended attribute SET operations
321 setxattr(struct dentry *d, const char __user *name, const void __user *value,
322 size_t size, int flags)
326 void *vvalue = NULL; /* If non-NULL, we used vmalloc() */
327 char kname[XATTR_NAME_MAX + 1];
329 if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
332 error = strncpy_from_user(kname, name, sizeof(kname));
333 if (error == 0 || error == sizeof(kname))
339 if (size > XATTR_SIZE_MAX)
341 kvalue = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
343 vvalue = vmalloc(size);
348 if (copy_from_user(kvalue, value, size)) {
354 error = vfs_setxattr(d, kname, kvalue, size, flags);
363 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
364 const char __user *, name, const void __user *, value,
365 size_t, size, int, flags)
370 error = user_path(pathname, &path);
373 error = mnt_want_write(path.mnt);
375 error = setxattr(path.dentry, name, value, size, flags);
376 mnt_drop_write(path.mnt);
382 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
383 const char __user *, name, const void __user *, value,
384 size_t, size, int, flags)
389 error = user_lpath(pathname, &path);
392 error = mnt_want_write(path.mnt);
394 error = setxattr(path.dentry, name, value, size, flags);
395 mnt_drop_write(path.mnt);
401 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
402 const void __user *,value, size_t, size, int, flags)
406 struct dentry *dentry;
409 f = fget_light(fd, &fput_needed);
412 dentry = f->f_path.dentry;
413 audit_inode(NULL, dentry);
414 error = mnt_want_write_file(f);
416 error = setxattr(dentry, name, value, size, flags);
417 mnt_drop_write_file(f);
419 fput_light(f, fput_needed);
424 * Extended attribute GET operations
427 getxattr(struct dentry *d, const char __user *name, void __user *value,
433 char kname[XATTR_NAME_MAX + 1];
435 error = strncpy_from_user(kname, name, sizeof(kname));
436 if (error == 0 || error == sizeof(kname))
442 if (size > XATTR_SIZE_MAX)
443 size = XATTR_SIZE_MAX;
444 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
446 vvalue = vmalloc(size);
453 error = vfs_getxattr(d, kname, kvalue, size);
455 if (size && copy_to_user(value, kvalue, error))
457 } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
458 /* The file system tried to returned a value bigger
459 than XATTR_SIZE_MAX bytes. Not possible. */
469 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
470 const char __user *, name, void __user *, value, size_t, size)
475 error = user_path(pathname, &path);
478 error = getxattr(path.dentry, name, value, size);
483 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
484 const char __user *, name, void __user *, value, size_t, size)
489 error = user_lpath(pathname, &path);
492 error = getxattr(path.dentry, name, value, size);
497 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
498 void __user *, value, size_t, size)
502 ssize_t error = -EBADF;
504 f = fget_light(fd, &fput_needed);
507 audit_inode(NULL, f->f_path.dentry);
508 error = getxattr(f->f_path.dentry, name, value, size);
509 fput_light(f, fput_needed);
514 * Extended attribute LIST operations
517 listxattr(struct dentry *d, char __user *list, size_t size)
521 char *vlist = NULL; /* If non-NULL, we used vmalloc() */
524 if (size > XATTR_LIST_MAX)
525 size = XATTR_LIST_MAX;
526 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
528 vlist = vmalloc(size);
535 error = vfs_listxattr(d, klist, size);
537 if (size && copy_to_user(list, klist, error))
539 } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
540 /* The file system tried to returned a list bigger
541 than XATTR_LIST_MAX bytes. Not possible. */
551 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
557 error = user_path(pathname, &path);
560 error = listxattr(path.dentry, list, size);
565 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
571 error = user_lpath(pathname, &path);
574 error = listxattr(path.dentry, list, size);
579 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
583 ssize_t error = -EBADF;
585 f = fget_light(fd, &fput_needed);
588 audit_inode(NULL, f->f_path.dentry);
589 error = listxattr(f->f_path.dentry, list, size);
590 fput_light(f, fput_needed);
595 * Extended attribute REMOVE operations
598 removexattr(struct dentry *d, const char __user *name)
601 char kname[XATTR_NAME_MAX + 1];
603 error = strncpy_from_user(kname, name, sizeof(kname));
604 if (error == 0 || error == sizeof(kname))
609 return vfs_removexattr(d, kname);
612 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
613 const char __user *, name)
618 error = user_path(pathname, &path);
621 error = mnt_want_write(path.mnt);
623 error = removexattr(path.dentry, name);
624 mnt_drop_write(path.mnt);
630 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
631 const char __user *, name)
636 error = user_lpath(pathname, &path);
639 error = mnt_want_write(path.mnt);
641 error = removexattr(path.dentry, name);
642 mnt_drop_write(path.mnt);
648 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
652 struct dentry *dentry;
655 f = fget_light(fd, &fput_needed);
658 dentry = f->f_path.dentry;
659 audit_inode(NULL, dentry);
660 error = mnt_want_write_file(f);
662 error = removexattr(dentry, name);
663 mnt_drop_write_file(f);
665 fput_light(f, fput_needed);
671 strcmp_prefix(const char *a, const char *a_prefix)
673 while (*a_prefix && *a == *a_prefix) {
677 return *a_prefix ? NULL : a;
681 * In order to implement different sets of xattr operations for each xattr
682 * prefix with the generic xattr API, a filesystem should create a
683 * null-terminated array of struct xattr_handler (one for each prefix) and
684 * hang a pointer to it off of the s_xattr field of the superblock.
686 * The generic_fooxattr() functions will use this list to dispatch xattr
687 * operations to the correct xattr_handler.
689 #define for_each_xattr_handler(handlers, handler) \
690 for ((handler) = *(handlers)++; \
692 (handler) = *(handlers)++)
695 * Find the xattr_handler with the matching prefix.
697 static const struct xattr_handler *
698 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
700 const struct xattr_handler *handler;
705 for_each_xattr_handler(handlers, handler) {
706 const char *n = strcmp_prefix(*name, handler->prefix);
716 * Find the handler for the prefix and dispatch its get() operation.
719 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
721 const struct xattr_handler *handler;
723 handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
726 return handler->get(dentry, name, buffer, size, handler->flags);
730 * Combine the results of the list() operation from every xattr_handler in the
734 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
736 const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
737 unsigned int size = 0;
740 for_each_xattr_handler(handlers, handler) {
741 size += handler->list(dentry, NULL, 0, NULL, 0,
747 for_each_xattr_handler(handlers, handler) {
748 size = handler->list(dentry, buf, buffer_size,
749 NULL, 0, handler->flags);
750 if (size > buffer_size)
761 * Find the handler for the prefix and dispatch its set() operation.
764 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
766 const struct xattr_handler *handler;
769 value = ""; /* empty EA, do not remove */
770 handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
773 return handler->set(dentry, name, value, size, flags, handler->flags);
777 * Find the handler for the prefix and dispatch its set() operation to remove
778 * any associated extended attribute.
781 generic_removexattr(struct dentry *dentry, const char *name)
783 const struct xattr_handler *handler;
785 handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
788 return handler->set(dentry, name, NULL, 0,
789 XATTR_REPLACE, handler->flags);
792 EXPORT_SYMBOL(generic_getxattr);
793 EXPORT_SYMBOL(generic_listxattr);
794 EXPORT_SYMBOL(generic_setxattr);
795 EXPORT_SYMBOL(generic_removexattr);