2 * Copyright (C) 2011 Novell Inc.
3 * Copyright (C) 2016 Red Hat, 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/cred.h>
12 #include <linux/namei.h>
13 #include <linux/xattr.h>
14 #include <linux/ratelimit.h>
15 #include <linux/mount.h>
16 #include <linux/exportfs.h>
17 #include "overlayfs.h"
18 #include "ovl_entry.h"
20 struct ovl_lookup_data {
29 static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d,
30 size_t prelen, const char *post)
33 char *s, *next, *buf = NULL;
35 res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, NULL, 0);
37 if (res == -ENODATA || res == -EOPNOTSUPP)
41 buf = kzalloc(prelen + res + strlen(post) + 1, GFP_TEMPORARY);
48 res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, buf, res);
54 for (s = buf; *s++ == '/'; s = next) {
55 next = strchrnul(s, '/');
60 if (strchr(buf, '/') != NULL)
63 memmove(buf + prelen, buf, res);
64 memcpy(buf, d->name.name, prelen);
70 d->name.name = d->redirect;
71 d->name.len = strlen(d->redirect);
79 pr_warn_ratelimited("overlayfs: failed to get redirect (%i)\n", res);
82 pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf);
86 static int ovl_acceptable(void *ctx, struct dentry *dentry)
91 static struct dentry *ovl_get_origin(struct dentry *dentry,
95 struct ovl_fh *fh = NULL;
96 struct dentry *origin = NULL;
99 res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);
101 if (res == -ENODATA || res == -EOPNOTSUPP)
105 /* Zero size value means "copied up but origin unknown" */
109 fh = kzalloc(res, GFP_TEMPORARY);
111 return ERR_PTR(-ENOMEM);
113 res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, fh, res);
117 if (res < sizeof(struct ovl_fh) || res < fh->len)
120 if (fh->magic != OVL_FH_MAGIC)
123 /* Treat larger version and unknown flags as "origin unknown" */
124 if (fh->version > OVL_FH_VERSION || fh->flags & ~OVL_FH_FLAG_ALL)
127 /* Treat endianness mismatch as "origin unknown" */
128 if (!(fh->flags & OVL_FH_FLAG_ANY_ENDIAN) &&
129 (fh->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN)
132 bytes = (fh->len - offsetof(struct ovl_fh, fid));
135 * Make sure that the stored uuid matches the uuid of the lower
136 * layer where file handle will be decoded.
138 if (!uuid_equal(&fh->uuid, &mnt->mnt_sb->s_uuid))
141 origin = exportfs_decode_fh(mnt, (struct fid *)fh->fid,
142 bytes >> 2, (int)fh->type,
143 ovl_acceptable, NULL);
144 if (IS_ERR(origin)) {
145 /* Treat stale file handle as "origin unknown" */
146 if (origin == ERR_PTR(-ESTALE))
151 if (ovl_dentry_weird(origin) ||
152 ((d_inode(origin)->i_mode ^ d_inode(dentry)->i_mode) & S_IFMT)) {
163 pr_warn_ratelimited("overlayfs: failed to get origin (%i)\n", res);
166 pr_warn_ratelimited("overlayfs: invalid origin (%*phN)\n", res, fh);
170 static bool ovl_is_opaquedir(struct dentry *dentry)
172 return ovl_check_dir_xattr(dentry, OVL_XATTR_OPAQUE);
175 static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
176 const char *name, unsigned int namelen,
177 size_t prelen, const char *post,
183 this = lookup_one_len_unlocked(name, base, namelen);
187 if (err == -ENOENT || err == -ENAMETOOLONG)
194 if (ovl_dentry_weird(this)) {
195 /* Don't support traversing automounts and other weirdness */
199 if (ovl_is_whiteout(this)) {
200 d->stop = d->opaque = true;
203 if (!d_can_lookup(this)) {
210 if (!d->last && ovl_is_opaquedir(this)) {
211 d->stop = d->opaque = true;
214 err = ovl_check_redirect(this, d, prelen, post);
231 static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
234 /* Counting down from the end, since the prefix can change */
235 size_t rem = d->name.len - 1;
236 struct dentry *dentry = NULL;
239 if (d->name.name[0] != '/')
240 return ovl_lookup_single(base, d, d->name.name, d->name.len,
243 while (!IS_ERR_OR_NULL(base) && d_can_lookup(base)) {
244 const char *s = d->name.name + d->name.len - rem;
245 const char *next = strchrnul(s, '/');
246 size_t thislen = next - s;
249 /* Verify we did not go off the rails */
250 if (WARN_ON(s[-1] != '/'))
253 err = ovl_lookup_single(base, d, s, thislen,
254 d->name.len - rem, next, &base);
264 if (WARN_ON(rem >= d->name.len))
272 static int ovl_check_origin(struct dentry *dentry, struct dentry *upperdentry,
273 struct path **stackp, unsigned int *ctrp)
275 struct super_block *same_sb = ovl_same_sb(dentry->d_sb);
276 struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata;
277 struct vfsmount *mnt;
278 struct dentry *origin;
280 if (!same_sb || !roe->numlower)
284 * Since all layers are on the same fs, we use the first layer for
285 * decoding the file handle. We may get a disconnected dentry,
286 * which is fine, because we only need to hold the origin inode in
287 * cache and use its inode number. We may even get a connected dentry,
288 * that is not under the first layer's root. That is also fine for
289 * using it's inode number - it's the same as if we held a reference
290 * to a dentry in first layer that was moved under us.
292 mnt = roe->lowerstack[0].mnt;
294 origin = ovl_get_origin(upperdentry, mnt);
295 if (IS_ERR_OR_NULL(origin))
296 return PTR_ERR(origin);
298 BUG_ON(*stackp || *ctrp);
299 *stackp = kmalloc(sizeof(struct path), GFP_TEMPORARY);
304 **stackp = (struct path) { .dentry = origin, .mnt = mnt };
311 * Returns next layer in stack starting from top.
312 * Returns -1 if this is the last layer.
314 int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
316 struct ovl_entry *oe = dentry->d_fsdata;
320 ovl_path_upper(dentry, path);
322 return oe->numlower ? 1 : -1;
325 BUG_ON(idx > oe->numlower);
326 *path = oe->lowerstack[idx - 1];
328 return (idx < oe->numlower) ? idx + 1 : -1;
331 struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
334 struct ovl_entry *oe;
335 const struct cred *old_cred;
336 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
337 struct ovl_entry *poe = dentry->d_parent->d_fsdata;
338 struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata;
339 struct path *stack = NULL;
340 struct dentry *upperdir, *upperdentry = NULL;
341 unsigned int ctr = 0;
342 struct inode *inode = NULL;
343 bool upperopaque = false;
344 bool upperimpure = false;
345 char *upperredirect = NULL;
349 struct ovl_lookup_data d = {
350 .name = dentry->d_name,
354 .last = !poe->numlower,
358 if (dentry->d_name.len > ofs->namelen)
359 return ERR_PTR(-ENAMETOOLONG);
361 old_cred = ovl_override_creds(dentry->d_sb);
362 upperdir = ovl_dentry_upper(dentry->d_parent);
364 err = ovl_lookup_layer(upperdir, &d, &upperdentry);
368 if (upperdentry && unlikely(ovl_dentry_remote(upperdentry))) {
373 if (upperdentry && !d.is_dir) {
374 BUG_ON(!d.stop || d.redirect);
375 err = ovl_check_origin(dentry, upperdentry,
382 upperredirect = kstrdup(d.redirect, GFP_KERNEL);
385 if (d.redirect[0] == '/')
388 upperopaque = d.opaque;
389 if (upperdentry && d.is_dir)
390 upperimpure = ovl_is_impuredir(upperdentry);
393 if (!d.stop && poe->numlower) {
395 stack = kcalloc(ofs->numlower, sizeof(struct path),
401 for (i = 0; !d.stop && i < poe->numlower; i++) {
402 struct path lowerpath = poe->lowerstack[i];
404 d.last = i == poe->numlower - 1;
405 err = ovl_lookup_layer(lowerpath.dentry, &d, &this);
412 stack[ctr].dentry = this;
413 stack[ctr].mnt = lowerpath.mnt;
419 if (d.redirect && d.redirect[0] == '/' && poe != roe) {
422 /* Find the current layer on the root dentry */
423 for (i = 0; i < poe->numlower; i++)
424 if (poe->lowerstack[i].mnt == lowerpath.mnt)
426 if (WARN_ON(i == poe->numlower))
431 oe = ovl_alloc_entry(ctr);
436 oe->opaque = upperopaque;
437 oe->impure = upperimpure;
438 memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
439 dentry->d_fsdata = oe;
441 if (upperdentry || ctr) {
443 inode = ovl_get_inode(dentry, upperdentry);
447 OVL_I(inode)->redirect = upperredirect;
450 revert_creds(old_cred);
453 d_add(dentry, inode);
458 dentry->d_fsdata = NULL;
461 for (i = 0; i < ctr; i++)
462 dput(stack[i].dentry);
466 kfree(upperredirect);
469 revert_creds(old_cred);
473 bool ovl_lower_positive(struct dentry *dentry)
475 struct ovl_entry *oe = dentry->d_fsdata;
476 struct ovl_entry *poe = dentry->d_parent->d_fsdata;
477 const struct qstr *name = &dentry->d_name;
479 bool positive = false;
483 * If dentry is negative, then lower is positive iff this is a
486 if (!dentry->d_inode)
489 /* Negative upper -> positive lower */
490 if (!ovl_dentry_upper(dentry))
493 /* Positive upper -> have to look up lower to see whether it exists */
494 for (i = 0; !done && !positive && i < poe->numlower; i++) {
496 struct dentry *lowerdir = poe->lowerstack[i].dentry;
498 this = lookup_one_len_unlocked(name->name, lowerdir,
501 switch (PTR_ERR(this)) {
508 * Assume something is there, we just couldn't
516 positive = !ovl_is_whiteout(this);