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;
44 const struct cred *old_cred;
47 * Check for permissions before trying to copy-up. This is redundant
48 * since it will be rechecked later by ->setattr() on upper dentry. But
49 * without this, copy-up can be triggered by just about anybody.
51 * We don't initialize inode->size, which just means that
52 * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
53 * check for a swapfile (which this won't be anyway).
55 err = inode_change_ok(dentry->d_inode, attr);
59 err = ovl_want_write(dentry);
63 if (attr->ia_valid & ATTR_SIZE) {
64 struct inode *realinode = d_inode(ovl_dentry_real(dentry));
67 if (atomic_read(&realinode->i_writecount) < 0)
71 err = ovl_copy_up(dentry);
73 struct inode *winode = NULL;
75 upperdentry = ovl_dentry_upper(dentry);
77 if (attr->ia_valid & ATTR_SIZE) {
78 winode = d_inode(upperdentry);
79 err = get_write_access(winode);
84 if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
85 attr->ia_valid &= ~ATTR_MODE;
87 inode_lock(upperdentry->d_inode);
88 old_cred = ovl_override_creds(dentry->d_sb);
89 err = notify_change(upperdentry, attr, NULL);
90 revert_creds(old_cred);
92 ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
93 inode_unlock(upperdentry->d_inode);
96 put_write_access(winode);
99 ovl_drop_write(dentry);
104 static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
107 struct path realpath;
108 const struct cred *old_cred;
111 ovl_path_real(dentry, &realpath);
112 old_cred = ovl_override_creds(dentry->d_sb);
113 err = vfs_getattr(&realpath, stat);
114 revert_creds(old_cred);
118 int ovl_permission(struct inode *inode, int mask)
121 struct inode *realinode = ovl_inode_real(inode, &is_upper);
122 const struct cred *old_cred;
125 /* Careful in RCU walk mode */
127 WARN_ON(!(mask & MAY_NOT_BLOCK));
132 * Check overlay inode with the creds of task and underlying inode
133 * with creds of mounter
135 err = generic_permission(inode, mask);
139 old_cred = ovl_override_creds(inode->i_sb);
140 if (!is_upper && !special_file(realinode->i_mode))
141 mask &= ~(MAY_WRITE | MAY_APPEND);
142 err = inode_permission(realinode, mask);
143 revert_creds(old_cred);
148 static const char *ovl_get_link(struct dentry *dentry,
150 struct delayed_call *done)
152 struct dentry *realdentry;
153 struct inode *realinode;
154 const struct cred *old_cred;
158 return ERR_PTR(-ECHILD);
160 realdentry = ovl_dentry_real(dentry);
161 realinode = realdentry->d_inode;
163 if (WARN_ON(!realinode->i_op->get_link))
164 return ERR_PTR(-EPERM);
166 old_cred = ovl_override_creds(dentry->d_sb);
167 p = realinode->i_op->get_link(realdentry, realinode, done);
168 revert_creds(old_cred);
172 static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
174 struct path realpath;
175 struct inode *realinode;
176 const struct cred *old_cred;
179 ovl_path_real(dentry, &realpath);
180 realinode = realpath.dentry->d_inode;
182 if (!realinode->i_op->readlink)
185 old_cred = ovl_override_creds(dentry->d_sb);
186 err = realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
187 revert_creds(old_cred);
191 static bool ovl_is_private_xattr(const char *name)
193 #define OVL_XATTR_PRE_NAME OVL_XATTR_PREFIX "."
194 return strncmp(name, OVL_XATTR_PRE_NAME,
195 sizeof(OVL_XATTR_PRE_NAME) - 1) == 0;
198 int ovl_setxattr(struct dentry *dentry, struct inode *inode,
199 const char *name, const void *value,
200 size_t size, int flags)
203 struct dentry *upperdentry;
204 const struct cred *old_cred;
206 err = ovl_want_write(dentry);
210 err = ovl_copy_up(dentry);
214 upperdentry = ovl_dentry_upper(dentry);
215 old_cred = ovl_override_creds(dentry->d_sb);
216 err = vfs_setxattr(upperdentry, name, value, size, flags);
217 revert_creds(old_cred);
220 ovl_drop_write(dentry);
225 ssize_t ovl_getxattr(struct dentry *dentry, struct inode *inode,
226 const char *name, void *value, size_t size)
228 struct dentry *realdentry = ovl_dentry_real(dentry);
230 const struct cred *old_cred;
232 if (ovl_is_private_xattr(name))
235 old_cred = ovl_override_creds(dentry->d_sb);
236 res = vfs_getxattr(realdentry, name, value, size);
237 revert_creds(old_cred);
241 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
243 struct dentry *realdentry = ovl_dentry_real(dentry);
246 const struct cred *old_cred;
248 old_cred = ovl_override_creds(dentry->d_sb);
249 res = vfs_listxattr(realdentry, list, size);
250 revert_creds(old_cred);
251 if (res <= 0 || size == 0)
254 /* filter out private xattrs */
255 for (off = 0; off < res;) {
256 char *s = list + off;
257 size_t slen = strlen(s) + 1;
259 BUG_ON(off + slen > res);
261 if (ovl_is_private_xattr(s)) {
263 memmove(s, s + slen, res - off);
272 int ovl_removexattr(struct dentry *dentry, const char *name)
275 struct path realpath;
276 enum ovl_path_type type = ovl_path_real(dentry, &realpath);
277 const struct cred *old_cred;
279 err = ovl_want_write(dentry);
284 if (ovl_is_private_xattr(name))
287 if (!OVL_TYPE_UPPER(type)) {
288 err = vfs_getxattr(realpath.dentry, name, NULL, 0);
292 err = ovl_copy_up(dentry);
296 ovl_path_upper(dentry, &realpath);
299 old_cred = ovl_override_creds(dentry->d_sb);
300 err = vfs_removexattr(realpath.dentry, name);
301 revert_creds(old_cred);
303 ovl_drop_write(dentry);
308 struct posix_acl *ovl_get_acl(struct inode *inode, int type)
310 struct inode *realinode = ovl_inode_real(inode, NULL);
311 const struct cred *old_cred;
312 struct posix_acl *acl;
314 if (!IS_POSIXACL(realinode))
317 if (!realinode->i_op->get_acl)
320 old_cred = ovl_override_creds(inode->i_sb);
321 acl = realinode->i_op->get_acl(realinode, type);
322 revert_creds(old_cred);
327 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
328 struct dentry *realdentry)
330 if (OVL_TYPE_UPPER(type))
333 if (special_file(realdentry->d_inode->i_mode))
336 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
342 int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags)
345 struct path realpath;
346 enum ovl_path_type type;
348 type = ovl_path_real(dentry, &realpath);
349 if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
350 err = ovl_want_write(dentry);
352 if (file_flags & O_TRUNC)
353 err = ovl_copy_up_truncate(dentry);
355 err = ovl_copy_up(dentry);
356 ovl_drop_write(dentry);
363 int ovl_update_time(struct inode *inode, struct timespec *ts, int flags)
365 struct dentry *alias;
366 struct path upperpath;
368 if (!(flags & S_ATIME))
371 alias = d_find_any_alias(inode);
375 ovl_path_upper(alias, &upperpath);
376 if (upperpath.dentry) {
377 touch_atime(&upperpath);
378 inode->i_atime = d_inode(upperpath.dentry)->i_atime;
386 static const struct inode_operations ovl_file_inode_operations = {
387 .setattr = ovl_setattr,
388 .permission = ovl_permission,
389 .getattr = ovl_getattr,
390 .setxattr = generic_setxattr,
391 .getxattr = ovl_getxattr,
392 .listxattr = ovl_listxattr,
393 .removexattr = ovl_removexattr,
394 .get_acl = ovl_get_acl,
395 .update_time = ovl_update_time,
398 static const struct inode_operations ovl_symlink_inode_operations = {
399 .setattr = ovl_setattr,
400 .get_link = ovl_get_link,
401 .readlink = ovl_readlink,
402 .getattr = ovl_getattr,
403 .setxattr = generic_setxattr,
404 .getxattr = ovl_getxattr,
405 .listxattr = ovl_listxattr,
406 .removexattr = ovl_removexattr,
407 .update_time = ovl_update_time,
410 static void ovl_fill_inode(struct inode *inode, umode_t mode)
412 inode->i_ino = get_next_ino();
413 inode->i_mode = mode;
414 inode->i_flags |= S_NOCMTIME;
419 inode->i_op = &ovl_dir_inode_operations;
420 inode->i_fop = &ovl_dir_operations;
424 inode->i_op = &ovl_symlink_inode_operations;
428 WARN(1, "illegal file type: %i\n", mode);
436 inode->i_op = &ovl_file_inode_operations;
441 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode)
445 inode = new_inode(sb);
447 ovl_fill_inode(inode, mode);
452 static int ovl_inode_test(struct inode *inode, void *data)
454 return ovl_inode_real(inode, NULL) == data;
457 static int ovl_inode_set(struct inode *inode, void *data)
459 inode->i_private = (void *) (((unsigned long) data) | OVL_ISUPPER_MASK);
463 struct inode *ovl_get_inode(struct super_block *sb, struct inode *realinode)
468 inode = iget5_locked(sb, (unsigned long) realinode,
469 ovl_inode_test, ovl_inode_set, realinode);
470 if (inode && inode->i_state & I_NEW) {
471 ovl_fill_inode(inode, realinode->i_mode);
472 set_nlink(inode, realinode->i_nlink);
473 unlock_new_inode(inode);