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 "overlayfs.h"
15 static int ovl_copy_up_last(struct dentry *dentry, struct iattr *attr,
19 struct dentry *parent;
21 struct path lowerpath;
23 parent = dget_parent(dentry);
24 err = ovl_copy_up(parent);
28 ovl_path_lower(dentry, &lowerpath);
29 err = vfs_getattr(&lowerpath, &stat);
36 err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat, attr);
43 int ovl_setattr(struct dentry *dentry, struct iattr *attr)
46 struct dentry *upperdentry;
48 err = ovl_want_write(dentry);
52 upperdentry = ovl_dentry_upper(dentry);
54 mutex_lock(&upperdentry->d_inode->i_mutex);
55 err = notify_change(upperdentry, attr, NULL);
56 mutex_unlock(&upperdentry->d_inode->i_mutex);
58 err = ovl_copy_up_last(dentry, attr, false);
60 ovl_drop_write(dentry);
65 static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
70 ovl_path_real(dentry, &realpath);
71 return vfs_getattr(&realpath, stat);
74 int ovl_permission(struct inode *inode, int mask)
77 struct dentry *alias = NULL;
78 struct inode *realinode;
79 struct dentry *realdentry;
83 if (S_ISDIR(inode->i_mode)) {
84 oe = inode->i_private;
85 } else if (mask & MAY_NOT_BLOCK) {
89 * For non-directories find an alias and get the info
92 alias = d_find_any_alias(inode);
99 realdentry = ovl_entry_real(oe, &is_upper);
101 /* Careful in RCU walk mode */
102 realinode = ACCESS_ONCE(realdentry->d_inode);
104 WARN_ON(!(mask & MAY_NOT_BLOCK));
109 if (mask & MAY_WRITE) {
110 umode_t mode = realinode->i_mode;
113 * Writes will always be redirected to upper layer, so
114 * ignore lower layer being read-only.
116 * If the overlay itself is read-only then proceed
117 * with the permission check, don't return EROFS.
118 * This will only happen if this is the lower layer of
121 * If upper fs becomes read-only after the overlay was
122 * constructed return EROFS to prevent modification of
126 if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
127 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
131 err = __inode_permission(realinode, mask);
138 struct ovl_link_data {
139 struct dentry *realdentry;
143 static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd)
146 struct dentry *realdentry;
147 struct inode *realinode;
149 realdentry = ovl_dentry_real(dentry);
150 realinode = realdentry->d_inode;
152 if (WARN_ON(!realinode->i_op->follow_link))
153 return ERR_PTR(-EPERM);
155 ret = realinode->i_op->follow_link(realdentry, nd);
159 if (realinode->i_op->put_link) {
160 struct ovl_link_data *data;
162 data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
164 realinode->i_op->put_link(realdentry, nd, ret);
165 return ERR_PTR(-ENOMEM);
167 data->realdentry = realdentry;
176 static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c)
178 struct inode *realinode;
179 struct ovl_link_data *data = c;
184 realinode = data->realdentry->d_inode;
185 realinode->i_op->put_link(data->realdentry, nd, data->cookie);
189 static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
191 struct path realpath;
192 struct inode *realinode;
194 ovl_path_real(dentry, &realpath);
195 realinode = realpath.dentry->d_inode;
197 if (!realinode->i_op->readlink)
200 touch_atime(&realpath);
202 return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
206 static bool ovl_is_private_xattr(const char *name)
208 return strncmp(name, "trusted.overlay.", 14) == 0;
211 int ovl_setxattr(struct dentry *dentry, const char *name,
212 const void *value, size_t size, int flags)
215 struct dentry *upperdentry;
217 err = ovl_want_write(dentry);
222 if (ovl_is_private_xattr(name))
225 err = ovl_copy_up(dentry);
229 upperdentry = ovl_dentry_upper(dentry);
230 err = vfs_setxattr(upperdentry, name, value, size, flags);
233 ovl_drop_write(dentry);
238 static bool ovl_need_xattr_filter(struct dentry *dentry,
239 enum ovl_path_type type)
241 return type == OVL_PATH_UPPER && S_ISDIR(dentry->d_inode->i_mode);
244 ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
245 void *value, size_t size)
247 struct path realpath;
248 enum ovl_path_type type = ovl_path_real(dentry, &realpath);
250 if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))
253 return vfs_getxattr(realpath.dentry, name, value, size);
256 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
258 struct path realpath;
259 enum ovl_path_type type = ovl_path_real(dentry, &realpath);
263 res = vfs_listxattr(realpath.dentry, list, size);
264 if (res <= 0 || size == 0)
267 if (!ovl_need_xattr_filter(dentry, type))
270 /* filter out private xattrs */
271 for (off = 0; off < res;) {
272 char *s = list + off;
273 size_t slen = strlen(s) + 1;
275 BUG_ON(off + slen > res);
277 if (ovl_is_private_xattr(s)) {
279 memmove(s, s + slen, res - off);
288 int ovl_removexattr(struct dentry *dentry, const char *name)
291 struct path realpath;
292 enum ovl_path_type type = ovl_path_real(dentry, &realpath);
294 err = ovl_want_write(dentry);
299 if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))
302 if (type == OVL_PATH_LOWER) {
303 err = vfs_getxattr(realpath.dentry, name, NULL, 0);
307 err = ovl_copy_up(dentry);
311 ovl_path_upper(dentry, &realpath);
314 err = vfs_removexattr(realpath.dentry, name);
316 ovl_drop_write(dentry);
321 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
322 struct dentry *realdentry)
324 if (type != OVL_PATH_LOWER)
327 if (special_file(realdentry->d_inode->i_mode))
330 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
336 static int ovl_dentry_open(struct dentry *dentry, struct file *file,
337 const struct cred *cred)
340 struct path realpath;
341 enum ovl_path_type type;
342 bool want_write = false;
344 type = ovl_path_real(dentry, &realpath);
345 if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) {
347 err = ovl_want_write(dentry);
351 if (file->f_flags & O_TRUNC)
352 err = ovl_copy_up_last(dentry, NULL, true);
354 err = ovl_copy_up(dentry);
358 ovl_path_upper(dentry, &realpath);
361 err = vfs_open(&realpath, file, cred);
364 ovl_drop_write(dentry);
369 static const struct inode_operations ovl_file_inode_operations = {
370 .setattr = ovl_setattr,
371 .permission = ovl_permission,
372 .getattr = ovl_getattr,
373 .setxattr = ovl_setxattr,
374 .getxattr = ovl_getxattr,
375 .listxattr = ovl_listxattr,
376 .removexattr = ovl_removexattr,
377 .dentry_open = ovl_dentry_open,
380 static const struct inode_operations ovl_symlink_inode_operations = {
381 .setattr = ovl_setattr,
382 .follow_link = ovl_follow_link,
383 .put_link = ovl_put_link,
384 .readlink = ovl_readlink,
385 .getattr = ovl_getattr,
386 .setxattr = ovl_setxattr,
387 .getxattr = ovl_getxattr,
388 .listxattr = ovl_listxattr,
389 .removexattr = ovl_removexattr,
392 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
393 struct ovl_entry *oe)
397 inode = new_inode(sb);
403 inode->i_ino = get_next_ino();
404 inode->i_mode = mode;
405 inode->i_flags |= S_NOATIME | S_NOCMTIME;
409 inode->i_private = oe;
410 inode->i_op = &ovl_dir_inode_operations;
411 inode->i_fop = &ovl_dir_operations;
415 inode->i_op = &ovl_symlink_inode_operations;
423 inode->i_op = &ovl_file_inode_operations;
427 WARN(1, "illegal file type: %i\n", mode);