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_truncate(struct dentry *dentry)
18 struct dentry *parent;
20 struct path lowerpath;
22 parent = dget_parent(dentry);
23 err = ovl_copy_up(parent);
27 ovl_path_lower(dentry, &lowerpath);
28 err = vfs_getattr(&lowerpath, &stat);
33 err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
40 int ovl_setattr(struct dentry *dentry, struct iattr *attr)
43 struct dentry *upperdentry;
46 * Check for permissions before trying to copy-up. This is redundant
47 * since it will be rechecked later by ->setattr() on upper dentry. But
48 * without this, copy-up can be triggered by just about anybody.
50 * We don't initialize inode->size, which just means that
51 * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
52 * check for a swapfile (which this won't be anyway).
54 err = inode_change_ok(dentry->d_inode, attr);
58 err = ovl_want_write(dentry);
62 if (attr->ia_valid & ATTR_SIZE) {
63 struct inode *realinode = d_inode(ovl_dentry_real(dentry));
66 if (atomic_read(&realinode->i_writecount) < 0)
70 err = ovl_copy_up(dentry);
72 struct inode *winode = NULL;
74 upperdentry = ovl_dentry_upper(dentry);
76 if (attr->ia_valid & ATTR_SIZE) {
77 winode = d_inode(upperdentry);
78 err = get_write_access(winode);
83 inode_lock(upperdentry->d_inode);
84 err = notify_change(upperdentry, attr, NULL);
86 ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
87 inode_unlock(upperdentry->d_inode);
90 put_write_access(winode);
93 ovl_drop_write(dentry);
98 static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
101 struct path realpath;
103 ovl_path_real(dentry, &realpath);
104 return vfs_getattr(&realpath, stat);
107 int ovl_permission(struct inode *inode, int mask)
109 struct ovl_entry *oe;
110 struct dentry *alias = NULL;
111 struct inode *realinode;
112 struct dentry *realdentry;
116 if (S_ISDIR(inode->i_mode)) {
117 oe = inode->i_private;
118 } else if (mask & MAY_NOT_BLOCK) {
122 * For non-directories find an alias and get the info
125 alias = d_find_any_alias(inode);
129 oe = alias->d_fsdata;
132 realdentry = ovl_entry_real(oe, &is_upper);
134 if (ovl_is_default_permissions(inode)) {
136 struct path realpath = { .dentry = realdentry };
138 if (mask & MAY_NOT_BLOCK)
141 realpath.mnt = ovl_entry_mnt_real(oe, inode, is_upper);
143 err = vfs_getattr(&realpath, &stat);
148 if ((stat.mode ^ inode->i_mode) & S_IFMT)
151 inode->i_mode = stat.mode;
152 inode->i_uid = stat.uid;
153 inode->i_gid = stat.gid;
155 err = generic_permission(inode, mask);
159 /* Careful in RCU walk mode */
160 realinode = ACCESS_ONCE(realdentry->d_inode);
162 WARN_ON(!(mask & MAY_NOT_BLOCK));
167 if (mask & MAY_WRITE) {
168 umode_t mode = realinode->i_mode;
171 * Writes will always be redirected to upper layer, so
172 * ignore lower layer being read-only.
174 * If the overlay itself is read-only then proceed
175 * with the permission check, don't return EROFS.
176 * This will only happen if this is the lower layer of
179 * If upper fs becomes read-only after the overlay was
180 * constructed return EROFS to prevent modification of
184 if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
185 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
189 err = __inode_permission(realinode, mask);
195 static const char *ovl_get_link(struct dentry *dentry,
197 struct delayed_call *done)
199 struct dentry *realdentry;
200 struct inode *realinode;
203 return ERR_PTR(-ECHILD);
205 realdentry = ovl_dentry_real(dentry);
206 realinode = realdentry->d_inode;
208 if (WARN_ON(!realinode->i_op->get_link))
209 return ERR_PTR(-EPERM);
211 return realinode->i_op->get_link(realdentry, realinode, done);
214 static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
216 struct path realpath;
217 struct inode *realinode;
219 ovl_path_real(dentry, &realpath);
220 realinode = realpath.dentry->d_inode;
222 if (!realinode->i_op->readlink)
225 touch_atime(&realpath);
227 return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
231 static bool ovl_is_private_xattr(const char *name)
233 return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0;
236 int ovl_setxattr(struct dentry *dentry, struct inode *inode,
237 const char *name, const void *value,
238 size_t size, int flags)
241 struct dentry *upperdentry;
243 err = ovl_want_write(dentry);
248 if (ovl_is_private_xattr(name))
251 err = ovl_copy_up(dentry);
255 upperdentry = ovl_dentry_upper(dentry);
256 err = vfs_setxattr(upperdentry, name, value, size, flags);
259 ovl_drop_write(dentry);
264 ssize_t ovl_getxattr(struct dentry *dentry, struct inode *inode,
265 const char *name, void *value, size_t size)
267 struct dentry *realdentry = ovl_dentry_real(dentry);
269 if (ovl_is_private_xattr(name))
272 return vfs_getxattr(realdentry, name, value, size);
275 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
277 struct dentry *realdentry = ovl_dentry_real(dentry);
281 res = vfs_listxattr(realdentry, list, size);
282 if (res <= 0 || size == 0)
285 /* filter out private xattrs */
286 for (off = 0; off < res;) {
287 char *s = list + off;
288 size_t slen = strlen(s) + 1;
290 BUG_ON(off + slen > res);
292 if (ovl_is_private_xattr(s)) {
294 memmove(s, s + slen, res - off);
303 int ovl_removexattr(struct dentry *dentry, const char *name)
306 struct path realpath;
307 enum ovl_path_type type = ovl_path_real(dentry, &realpath);
309 err = ovl_want_write(dentry);
314 if (ovl_is_private_xattr(name))
317 if (!OVL_TYPE_UPPER(type)) {
318 err = vfs_getxattr(realpath.dentry, name, NULL, 0);
322 err = ovl_copy_up(dentry);
326 ovl_path_upper(dentry, &realpath);
329 err = vfs_removexattr(realpath.dentry, name);
331 ovl_drop_write(dentry);
336 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
337 struct dentry *realdentry)
339 if (OVL_TYPE_UPPER(type))
342 if (special_file(realdentry->d_inode->i_mode))
345 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
351 struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags)
354 struct path realpath;
355 enum ovl_path_type type;
357 if (d_is_dir(dentry))
358 return d_backing_inode(dentry);
360 type = ovl_path_real(dentry, &realpath);
361 if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
362 err = ovl_want_write(dentry);
366 if (file_flags & O_TRUNC)
367 err = ovl_copy_up_truncate(dentry);
369 err = ovl_copy_up(dentry);
370 ovl_drop_write(dentry);
374 ovl_path_upper(dentry, &realpath);
377 if (realpath.dentry->d_flags & DCACHE_OP_SELECT_INODE)
378 return realpath.dentry->d_op->d_select_inode(realpath.dentry, file_flags);
380 return d_backing_inode(realpath.dentry);
383 static const struct inode_operations ovl_file_inode_operations = {
384 .setattr = ovl_setattr,
385 .permission = ovl_permission,
386 .getattr = ovl_getattr,
387 .setxattr = ovl_setxattr,
388 .getxattr = ovl_getxattr,
389 .listxattr = ovl_listxattr,
390 .removexattr = ovl_removexattr,
393 static const struct inode_operations ovl_symlink_inode_operations = {
394 .setattr = ovl_setattr,
395 .get_link = ovl_get_link,
396 .readlink = ovl_readlink,
397 .getattr = ovl_getattr,
398 .setxattr = ovl_setxattr,
399 .getxattr = ovl_getxattr,
400 .listxattr = ovl_listxattr,
401 .removexattr = ovl_removexattr,
404 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
405 struct ovl_entry *oe)
409 inode = new_inode(sb);
415 inode->i_ino = get_next_ino();
416 inode->i_mode = mode;
417 inode->i_flags |= S_NOATIME | S_NOCMTIME;
421 inode->i_private = oe;
422 inode->i_op = &ovl_dir_inode_operations;
423 inode->i_fop = &ovl_dir_operations;
427 inode->i_op = &ovl_symlink_inode_operations;
435 inode->i_op = &ovl_file_inode_operations;
439 WARN(1, "illegal file type: %i\n", mode);