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_be_cmp(fh->uuid, *(uuid_be *) &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)
175 if (!d_is_dir(dentry))
178 res = vfs_getxattr(dentry, OVL_XATTR_OPAQUE, &val, 1);
179 if (res == 1 && val == 'y')
185 static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
186 const char *name, unsigned int namelen,
187 size_t prelen, const char *post,
193 this = lookup_one_len_unlocked(name, base, namelen);
197 if (err == -ENOENT || err == -ENAMETOOLONG)
204 if (ovl_dentry_weird(this)) {
205 /* Don't support traversing automounts and other weirdness */
209 if (ovl_is_whiteout(this)) {
210 d->stop = d->opaque = true;
213 if (!d_can_lookup(this)) {
220 if (!d->last && ovl_is_opaquedir(this)) {
221 d->stop = d->opaque = true;
224 err = ovl_check_redirect(this, d, prelen, post);
241 static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
244 /* Counting down from the end, since the prefix can change */
245 size_t rem = d->name.len - 1;
246 struct dentry *dentry = NULL;
249 if (d->name.name[0] != '/')
250 return ovl_lookup_single(base, d, d->name.name, d->name.len,
253 while (!IS_ERR_OR_NULL(base) && d_can_lookup(base)) {
254 const char *s = d->name.name + d->name.len - rem;
255 const char *next = strchrnul(s, '/');
256 size_t thislen = next - s;
259 /* Verify we did not go off the rails */
260 if (WARN_ON(s[-1] != '/'))
263 err = ovl_lookup_single(base, d, s, thislen,
264 d->name.len - rem, next, &base);
274 if (WARN_ON(rem >= d->name.len))
282 static int ovl_check_origin(struct dentry *dentry, struct dentry *upperdentry,
283 struct path **stackp, unsigned int *ctrp)
285 struct super_block *same_sb = ovl_same_sb(dentry->d_sb);
286 struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata;
287 struct vfsmount *mnt;
288 struct dentry *origin;
290 if (!same_sb || !roe->numlower)
294 * Since all layers are on the same fs, we use the first layer for
295 * decoding the file handle. We may get a disconnected dentry,
296 * which is fine, because we only need to hold the origin inode in
297 * cache and use its inode number. We may even get a connected dentry,
298 * that is not under the first layer's root. That is also fine for
299 * using it's inode number - it's the same as if we held a reference
300 * to a dentry in first layer that was moved under us.
302 mnt = roe->lowerstack[0].mnt;
304 origin = ovl_get_origin(upperdentry, mnt);
305 if (IS_ERR_OR_NULL(origin))
306 return PTR_ERR(origin);
308 BUG_ON(*stackp || *ctrp);
309 *stackp = kmalloc(sizeof(struct path), GFP_TEMPORARY);
314 **stackp = (struct path) { .dentry = origin, .mnt = mnt };
321 * Returns next layer in stack starting from top.
322 * Returns -1 if this is the last layer.
324 int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
326 struct ovl_entry *oe = dentry->d_fsdata;
330 ovl_path_upper(dentry, path);
332 return oe->numlower ? 1 : -1;
335 BUG_ON(idx > oe->numlower);
336 *path = oe->lowerstack[idx - 1];
338 return (idx < oe->numlower) ? idx + 1 : -1;
341 struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
344 struct ovl_entry *oe;
345 const struct cred *old_cred;
346 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
347 struct ovl_entry *poe = dentry->d_parent->d_fsdata;
348 struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata;
349 struct path *stack = NULL;
350 struct dentry *upperdir, *upperdentry = NULL;
351 unsigned int ctr = 0;
352 struct inode *inode = NULL;
353 bool upperopaque = false;
354 char *upperredirect = NULL;
358 struct ovl_lookup_data d = {
359 .name = dentry->d_name,
363 .last = !poe->numlower,
367 if (dentry->d_name.len > ofs->namelen)
368 return ERR_PTR(-ENAMETOOLONG);
370 old_cred = ovl_override_creds(dentry->d_sb);
371 upperdir = ovl_upperdentry_dereference(poe);
373 err = ovl_lookup_layer(upperdir, &d, &upperdentry);
377 if (upperdentry && unlikely(ovl_dentry_remote(upperdentry))) {
382 if (upperdentry && !d.is_dir) {
383 BUG_ON(!d.stop || d.redirect);
384 err = ovl_check_origin(dentry, upperdentry,
391 upperredirect = kstrdup(d.redirect, GFP_KERNEL);
394 if (d.redirect[0] == '/')
397 upperopaque = d.opaque;
400 if (!d.stop && poe->numlower) {
402 stack = kcalloc(ofs->numlower, sizeof(struct path),
408 for (i = 0; !d.stop && i < poe->numlower; i++) {
409 struct path lowerpath = poe->lowerstack[i];
411 d.last = i == poe->numlower - 1;
412 err = ovl_lookup_layer(lowerpath.dentry, &d, &this);
419 stack[ctr].dentry = this;
420 stack[ctr].mnt = lowerpath.mnt;
426 if (d.redirect && d.redirect[0] == '/' && poe != roe) {
429 /* Find the current layer on the root dentry */
430 for (i = 0; i < poe->numlower; i++)
431 if (poe->lowerstack[i].mnt == lowerpath.mnt)
433 if (WARN_ON(i == poe->numlower))
438 oe = ovl_alloc_entry(ctr);
443 if (upperdentry || ctr) {
444 struct dentry *realdentry;
445 struct inode *realinode;
447 realdentry = upperdentry ? upperdentry : stack[0].dentry;
448 realinode = d_inode(realdentry);
451 if (upperdentry && !d_is_dir(upperdentry)) {
452 inode = ovl_get_inode(dentry->d_sb, realinode);
454 inode = ovl_new_inode(dentry->d_sb, realinode->i_mode,
457 ovl_inode_init(inode, realinode, !!upperdentry);
461 ovl_copyattr(realdentry->d_inode, inode);
464 revert_creds(old_cred);
465 oe->opaque = upperopaque;
466 oe->redirect = upperredirect;
467 oe->__upperdentry = upperdentry;
468 memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
471 dentry->d_fsdata = oe;
472 d_add(dentry, inode);
479 for (i = 0; i < ctr; i++)
480 dput(stack[i].dentry);
484 kfree(upperredirect);
487 revert_creds(old_cred);
491 bool ovl_lower_positive(struct dentry *dentry)
493 struct ovl_entry *oe = dentry->d_fsdata;
494 struct ovl_entry *poe = dentry->d_parent->d_fsdata;
495 const struct qstr *name = &dentry->d_name;
497 bool positive = false;
501 * If dentry is negative, then lower is positive iff this is a
504 if (!dentry->d_inode)
507 /* Negative upper -> positive lower */
508 if (!oe->__upperdentry)
511 /* Positive upper -> have to look up lower to see whether it exists */
512 for (i = 0; !done && !positive && i < poe->numlower; i++) {
514 struct dentry *lowerdir = poe->lowerstack[i].dentry;
516 this = lookup_one_len_unlocked(name->name, lowerdir,
519 switch (PTR_ERR(this)) {
526 * Assume something is there, we just couldn't
534 positive = !ovl_is_whiteout(this);