3 * Copyright (C) 2011 Novell Inc.
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 as published by
7 * the Free Software Foundation.
11 #include <linux/slab.h>
12 #include <linux/xattr.h>
13 #include <linux/posix_acl.h>
14 #include "overlayfs.h"
16 int ovl_setattr(struct dentry *dentry, struct iattr *attr)
19 struct dentry *upperdentry;
20 const struct cred *old_cred;
23 * Check for permissions before trying to copy-up. This is redundant
24 * since it will be rechecked later by ->setattr() on upper dentry. But
25 * without this, copy-up can be triggered by just about anybody.
27 * We don't initialize inode->size, which just means that
28 * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
29 * check for a swapfile (which this won't be anyway).
31 err = setattr_prepare(dentry, attr);
35 err = ovl_want_write(dentry);
39 err = ovl_copy_up(dentry);
41 upperdentry = ovl_dentry_upper(dentry);
43 if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
44 attr->ia_valid &= ~ATTR_MODE;
46 inode_lock(upperdentry->d_inode);
47 old_cred = ovl_override_creds(dentry->d_sb);
48 err = notify_change(upperdentry, attr, NULL);
49 revert_creds(old_cred);
51 ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
52 inode_unlock(upperdentry->d_inode);
54 ovl_drop_write(dentry);
59 static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
63 const struct cred *old_cred;
66 ovl_path_real(dentry, &realpath);
67 old_cred = ovl_override_creds(dentry->d_sb);
68 err = vfs_getattr(&realpath, stat);
69 revert_creds(old_cred);
73 int ovl_permission(struct inode *inode, int mask)
76 struct inode *realinode = ovl_inode_real(inode, &is_upper);
77 const struct cred *old_cred;
80 /* Careful in RCU walk mode */
82 WARN_ON(!(mask & MAY_NOT_BLOCK));
87 * Check overlay inode with the creds of task and underlying inode
88 * with creds of mounter
90 err = generic_permission(inode, mask);
94 old_cred = ovl_override_creds(inode->i_sb);
95 if (!is_upper && !special_file(realinode->i_mode) && mask & MAY_WRITE) {
96 mask &= ~(MAY_WRITE | MAY_APPEND);
97 /* Make sure mounter can read file for copy up later */
100 err = inode_permission(realinode, mask);
101 revert_creds(old_cred);
106 static const char *ovl_get_link(struct dentry *dentry,
108 struct delayed_call *done)
110 const struct cred *old_cred;
114 return ERR_PTR(-ECHILD);
116 old_cred = ovl_override_creds(dentry->d_sb);
117 p = vfs_get_link(ovl_dentry_real(dentry), done);
118 revert_creds(old_cred);
122 bool ovl_is_private_xattr(const char *name)
124 return strncmp(name, OVL_XATTR_PREFIX,
125 sizeof(OVL_XATTR_PREFIX) - 1) == 0;
128 int ovl_xattr_set(struct dentry *dentry, const char *name, const void *value,
129 size_t size, int flags)
132 struct path realpath;
133 enum ovl_path_type type = ovl_path_real(dentry, &realpath);
134 const struct cred *old_cred;
136 err = ovl_want_write(dentry);
140 if (!value && !OVL_TYPE_UPPER(type)) {
141 err = vfs_getxattr(realpath.dentry, name, NULL, 0);
146 err = ovl_copy_up(dentry);
150 if (!OVL_TYPE_UPPER(type))
151 ovl_path_upper(dentry, &realpath);
153 old_cred = ovl_override_creds(dentry->d_sb);
155 err = vfs_setxattr(realpath.dentry, name, value, size, flags);
157 WARN_ON(flags != XATTR_REPLACE);
158 err = vfs_removexattr(realpath.dentry, name);
160 revert_creds(old_cred);
163 ovl_drop_write(dentry);
168 int ovl_xattr_get(struct dentry *dentry, const char *name,
169 void *value, size_t size)
171 struct dentry *realdentry = ovl_dentry_real(dentry);
173 const struct cred *old_cred;
175 old_cred = ovl_override_creds(dentry->d_sb);
176 res = vfs_getxattr(realdentry, name, value, size);
177 revert_creds(old_cred);
181 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
183 struct dentry *realdentry = ovl_dentry_real(dentry);
187 const struct cred *old_cred;
189 old_cred = ovl_override_creds(dentry->d_sb);
190 res = vfs_listxattr(realdentry, list, size);
191 revert_creds(old_cred);
192 if (res <= 0 || size == 0)
195 /* filter out private xattrs */
196 for (s = list, len = res; len;) {
197 size_t slen = strnlen(s, len) + 1;
199 /* underlying fs providing us with an broken xattr list? */
200 if (WARN_ON(slen > len))
204 if (ovl_is_private_xattr(s)) {
206 memmove(s, s + slen, len);
215 struct posix_acl *ovl_get_acl(struct inode *inode, int type)
217 struct inode *realinode = ovl_inode_real(inode, NULL);
218 const struct cred *old_cred;
219 struct posix_acl *acl;
221 if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
224 old_cred = ovl_override_creds(inode->i_sb);
225 acl = get_acl(realinode, type);
226 revert_creds(old_cred);
231 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
232 struct dentry *realdentry)
234 if (OVL_TYPE_UPPER(type))
237 if (special_file(realdentry->d_inode->i_mode))
240 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
246 int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags)
249 struct path realpath;
250 enum ovl_path_type type;
252 type = ovl_path_real(dentry, &realpath);
253 if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
254 err = ovl_want_write(dentry);
256 err = ovl_copy_up_flags(dentry, file_flags);
257 ovl_drop_write(dentry);
264 int ovl_update_time(struct inode *inode, struct timespec *ts, int flags)
266 struct dentry *alias;
267 struct path upperpath;
269 if (!(flags & S_ATIME))
272 alias = d_find_any_alias(inode);
276 ovl_path_upper(alias, &upperpath);
277 if (upperpath.dentry) {
278 touch_atime(&upperpath);
279 inode->i_atime = d_inode(upperpath.dentry)->i_atime;
287 static const struct inode_operations ovl_file_inode_operations = {
288 .setattr = ovl_setattr,
289 .permission = ovl_permission,
290 .getattr = ovl_getattr,
291 .listxattr = ovl_listxattr,
292 .get_acl = ovl_get_acl,
293 .update_time = ovl_update_time,
296 static const struct inode_operations ovl_symlink_inode_operations = {
297 .setattr = ovl_setattr,
298 .get_link = ovl_get_link,
299 .readlink = generic_readlink,
300 .getattr = ovl_getattr,
301 .listxattr = ovl_listxattr,
302 .update_time = ovl_update_time,
305 static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
307 inode->i_ino = get_next_ino();
308 inode->i_mode = mode;
309 inode->i_flags |= S_NOCMTIME;
310 #ifdef CONFIG_FS_POSIX_ACL
311 inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE;
314 switch (mode & S_IFMT) {
316 inode->i_op = &ovl_file_inode_operations;
320 inode->i_op = &ovl_dir_inode_operations;
321 inode->i_fop = &ovl_dir_operations;
325 inode->i_op = &ovl_symlink_inode_operations;
329 inode->i_op = &ovl_file_inode_operations;
330 init_special_inode(inode, mode, rdev);
335 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev)
339 inode = new_inode(sb);
341 ovl_fill_inode(inode, mode, rdev);
346 static int ovl_inode_test(struct inode *inode, void *data)
348 return ovl_inode_real(inode, NULL) == data;
351 static int ovl_inode_set(struct inode *inode, void *data)
353 inode->i_private = (void *) (((unsigned long) data) | OVL_ISUPPER_MASK);
357 struct inode *ovl_get_inode(struct super_block *sb, struct inode *realinode)
362 inode = iget5_locked(sb, (unsigned long) realinode,
363 ovl_inode_test, ovl_inode_set, realinode);
364 if (inode && inode->i_state & I_NEW) {
365 ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev);
366 set_nlink(inode, realinode->i_nlink);
367 unlock_new_inode(inode);