linux/fs/overlayfs/namei.c
Vivek Goyal d1fe96c0e4 ovl: redirect_dir=nofollow should not follow redirect for opaque lower
redirect_dir=nofollow should not follow a redirect. But in a specific
configuration it can still follow it.  For example try this.

$ mkdir -p lower0 lower1/foo upper work merged
$ touch lower1/foo/lower-file.txt
$ setfattr -n "trusted.overlay.opaque" -v "y" lower1/foo
$ mount -t overlay -o lowerdir=lower1:lower0,workdir=work,upperdir=upper,redirect_dir=on none merged
$ cd merged
$ mv foo foo-renamed
$ umount merged

# mount again. This time with redirect_dir=nofollow
$ mount -t overlay -o lowerdir=lower1:lower0,workdir=work,upperdir=upper,redirect_dir=nofollow none merged
$ ls merged/foo-renamed/
# This lists lower-file.txt, while it should not have.

Basically, we are doing redirect check after we check for d.stop. And
if this is not last lower, and we find an opaque lower, d.stop will be
set.

ovl_lookup_single()
        if (!d->last && ovl_is_opaquedir(this)) {
                d->stop = d->opaque = true;
                goto out;
        }

To fix this, first check redirect is allowed. And after that check if
d.stop has been set or not.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Fixes: 438c84c2f0 ("ovl: don't follow redirects if redirect_dir=off")
Cc: <stable@vger.kernel.org> #v4.15
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-02-26 16:55:51 +01:00

1069 lines
25 KiB
C

/*
* Copyright (C) 2011 Novell Inc.
* Copyright (C) 2016 Red Hat, Inc.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published by
* the Free Software Foundation.
*/
#include <linux/fs.h>
#include <linux/cred.h>
#include <linux/ctype.h>
#include <linux/namei.h>
#include <linux/xattr.h>
#include <linux/ratelimit.h>
#include <linux/mount.h>
#include <linux/exportfs.h>
#include "overlayfs.h"
struct ovl_lookup_data {
struct qstr name;
bool is_dir;
bool opaque;
bool stop;
bool last;
char *redirect;
};
static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d,
size_t prelen, const char *post)
{
int res;
char *s, *next, *buf = NULL;
res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, NULL, 0);
if (res < 0) {
if (res == -ENODATA || res == -EOPNOTSUPP)
return 0;
goto fail;
}
buf = kzalloc(prelen + res + strlen(post) + 1, GFP_KERNEL);
if (!buf)
return -ENOMEM;
if (res == 0)
goto invalid;
res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, buf, res);
if (res < 0)
goto fail;
if (res == 0)
goto invalid;
if (buf[0] == '/') {
for (s = buf; *s++ == '/'; s = next) {
next = strchrnul(s, '/');
if (s == next)
goto invalid;
}
} else {
if (strchr(buf, '/') != NULL)
goto invalid;
memmove(buf + prelen, buf, res);
memcpy(buf, d->name.name, prelen);
}
strcat(buf, post);
kfree(d->redirect);
d->redirect = buf;
d->name.name = d->redirect;
d->name.len = strlen(d->redirect);
return 0;
err_free:
kfree(buf);
return 0;
fail:
pr_warn_ratelimited("overlayfs: failed to get redirect (%i)\n", res);
goto err_free;
invalid:
pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf);
goto err_free;
}
static int ovl_acceptable(void *ctx, struct dentry *dentry)
{
/*
* A non-dir origin may be disconnected, which is fine, because
* we only need it for its unique inode number.
*/
if (!d_is_dir(dentry))
return 1;
/* Don't decode a deleted empty directory */
if (d_unhashed(dentry))
return 0;
/* Check if directory belongs to the layer we are decoding from */
return is_subdir(dentry, ((struct vfsmount *)ctx)->mnt_root);
}
/*
* Check validity of an overlay file handle buffer.
*
* Return 0 for a valid file handle.
* Return -ENODATA for "origin unknown".
* Return <0 for an invalid file handle.
*/
int ovl_check_fh_len(struct ovl_fh *fh, int fh_len)
{
if (fh_len < sizeof(struct ovl_fh) || fh_len < fh->len)
return -EINVAL;
if (fh->magic != OVL_FH_MAGIC)
return -EINVAL;
/* Treat larger version and unknown flags as "origin unknown" */
if (fh->version > OVL_FH_VERSION || fh->flags & ~OVL_FH_FLAG_ALL)
return -ENODATA;
/* Treat endianness mismatch as "origin unknown" */
if (!(fh->flags & OVL_FH_FLAG_ANY_ENDIAN) &&
(fh->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN)
return -ENODATA;
return 0;
}
static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name)
{
int res, err;
struct ovl_fh *fh = NULL;
res = vfs_getxattr(dentry, name, NULL, 0);
if (res < 0) {
if (res == -ENODATA || res == -EOPNOTSUPP)
return NULL;
goto fail;
}
/* Zero size value means "copied up but origin unknown" */
if (res == 0)
return NULL;
fh = kzalloc(res, GFP_KERNEL);
if (!fh)
return ERR_PTR(-ENOMEM);
res = vfs_getxattr(dentry, name, fh, res);
if (res < 0)
goto fail;
err = ovl_check_fh_len(fh, res);
if (err < 0) {
if (err == -ENODATA)
goto out;
goto invalid;
}
return fh;
out:
kfree(fh);
return NULL;
fail:
pr_warn_ratelimited("overlayfs: failed to get origin (%i)\n", res);
goto out;
invalid:
pr_warn_ratelimited("overlayfs: invalid origin (%*phN)\n", res, fh);
goto out;
}
struct dentry *ovl_decode_fh(struct ovl_fh *fh, struct vfsmount *mnt)
{
struct dentry *real;
int bytes;
/*
* Make sure that the stored uuid matches the uuid of the lower
* layer where file handle will be decoded.
*/
if (!uuid_equal(&fh->uuid, &mnt->mnt_sb->s_uuid))
return NULL;
bytes = (fh->len - offsetof(struct ovl_fh, fid));
real = exportfs_decode_fh(mnt, (struct fid *)fh->fid,
bytes >> 2, (int)fh->type,
ovl_acceptable, mnt);
if (IS_ERR(real)) {
/*
* Treat stale file handle to lower file as "origin unknown".
* upper file handle could become stale when upper file is
* unlinked and this information is needed to handle stale
* index entries correctly.
*/
if (real == ERR_PTR(-ESTALE) &&
!(fh->flags & OVL_FH_FLAG_PATH_UPPER))
real = NULL;
return real;
}
if (ovl_dentry_weird(real)) {
dput(real);
return NULL;
}
return real;
}
static bool ovl_is_opaquedir(struct dentry *dentry)
{
return ovl_check_dir_xattr(dentry, OVL_XATTR_OPAQUE);
}
static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
const char *name, unsigned int namelen,
size_t prelen, const char *post,
struct dentry **ret)
{
struct dentry *this;
int err;
this = lookup_one_len_unlocked(name, base, namelen);
if (IS_ERR(this)) {
err = PTR_ERR(this);
this = NULL;
if (err == -ENOENT || err == -ENAMETOOLONG)
goto out;
goto out_err;
}
if (!this->d_inode)
goto put_and_out;
if (ovl_dentry_weird(this)) {
/* Don't support traversing automounts and other weirdness */
err = -EREMOTE;
goto out_err;
}
if (ovl_is_whiteout(this)) {
d->stop = d->opaque = true;
goto put_and_out;
}
if (!d_can_lookup(this)) {
d->stop = true;
if (d->is_dir)
goto put_and_out;
goto out;
}
d->is_dir = true;
if (!d->last && ovl_is_opaquedir(this)) {
d->stop = d->opaque = true;
goto out;
}
err = ovl_check_redirect(this, d, prelen, post);
if (err)
goto out_err;
out:
*ret = this;
return 0;
put_and_out:
dput(this);
this = NULL;
goto out;
out_err:
dput(this);
return err;
}
static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
struct dentry **ret)
{
/* Counting down from the end, since the prefix can change */
size_t rem = d->name.len - 1;
struct dentry *dentry = NULL;
int err;
if (d->name.name[0] != '/')
return ovl_lookup_single(base, d, d->name.name, d->name.len,
0, "", ret);
while (!IS_ERR_OR_NULL(base) && d_can_lookup(base)) {
const char *s = d->name.name + d->name.len - rem;
const char *next = strchrnul(s, '/');
size_t thislen = next - s;
bool end = !next[0];
/* Verify we did not go off the rails */
if (WARN_ON(s[-1] != '/'))
return -EIO;
err = ovl_lookup_single(base, d, s, thislen,
d->name.len - rem, next, &base);
dput(dentry);
if (err)
return err;
dentry = base;
if (end)
break;
rem -= thislen + 1;
if (WARN_ON(rem >= d->name.len))
return -EIO;
}
*ret = dentry;
return 0;
}
int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh,
struct dentry *upperdentry, struct ovl_path **stackp)
{
struct dentry *origin = NULL;
int i;
for (i = 0; i < ofs->numlower; i++) {
origin = ovl_decode_fh(fh, ofs->lower_layers[i].mnt);
if (origin)
break;
}
if (!origin)
return -ESTALE;
else if (IS_ERR(origin))
return PTR_ERR(origin);
if (upperdentry && !ovl_is_whiteout(upperdentry) &&
((d_inode(origin)->i_mode ^ d_inode(upperdentry)->i_mode) & S_IFMT))
goto invalid;
if (!*stackp)
*stackp = kmalloc(sizeof(struct ovl_path), GFP_KERNEL);
if (!*stackp) {
dput(origin);
return -ENOMEM;
}
**stackp = (struct ovl_path){
.dentry = origin,
.layer = &ofs->lower_layers[i]
};
return 0;
invalid:
pr_warn_ratelimited("overlayfs: invalid origin (%pd2, ftype=%x, origin ftype=%x).\n",
upperdentry, d_inode(upperdentry)->i_mode & S_IFMT,
d_inode(origin)->i_mode & S_IFMT);
dput(origin);
return -EIO;
}
static int ovl_check_origin(struct ovl_fs *ofs, struct dentry *upperdentry,
struct ovl_path **stackp, unsigned int *ctrp)
{
struct ovl_fh *fh = ovl_get_fh(upperdentry, OVL_XATTR_ORIGIN);
int err;
if (IS_ERR_OR_NULL(fh))
return PTR_ERR(fh);
err = ovl_check_origin_fh(ofs, fh, upperdentry, stackp);
kfree(fh);
if (err) {
if (err == -ESTALE)
return 0;
return err;
}
if (WARN_ON(*ctrp))
return -EIO;
*ctrp = 1;
return 0;
}
/*
* Verify that @fh matches the file handle stored in xattr @name.
* Return 0 on match, -ESTALE on mismatch, < 0 on error.
*/
static int ovl_verify_fh(struct dentry *dentry, const char *name,
const struct ovl_fh *fh)
{
struct ovl_fh *ofh = ovl_get_fh(dentry, name);
int err = 0;
if (!ofh)
return -ENODATA;
if (IS_ERR(ofh))
return PTR_ERR(ofh);
if (fh->len != ofh->len || memcmp(fh, ofh, fh->len))
err = -ESTALE;
kfree(ofh);
return err;
}
/*
* Verify that @real dentry matches the file handle stored in xattr @name.
*
* If @set is true and there is no stored file handle, encode @real and store
* file handle in xattr @name.
*
* Return 0 on match, -ESTALE on mismatch, -ENODATA on no xattr, < 0 on error.
*/
int ovl_verify_set_fh(struct dentry *dentry, const char *name,
struct dentry *real, bool is_upper, bool set)
{
struct inode *inode;
struct ovl_fh *fh;
int err;
fh = ovl_encode_fh(real, is_upper);
err = PTR_ERR(fh);
if (IS_ERR(fh))
goto fail;
err = ovl_verify_fh(dentry, name, fh);
if (set && err == -ENODATA)
err = ovl_do_setxattr(dentry, name, fh, fh->len, 0);
if (err)
goto fail;
out:
kfree(fh);
return err;
fail:
inode = d_inode(real);
pr_warn_ratelimited("overlayfs: failed to verify %s (%pd2, ino=%lu, err=%i)\n",
is_upper ? "upper" : "origin", real,
inode ? inode->i_ino : 0, err);
goto out;
}
/* Get upper dentry from index */
struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index)
{
struct ovl_fh *fh;
struct dentry *upper;
if (!d_is_dir(index))
return dget(index);
fh = ovl_get_fh(index, OVL_XATTR_UPPER);
if (IS_ERR_OR_NULL(fh))
return ERR_CAST(fh);
upper = ovl_decode_fh(fh, ofs->upper_mnt);
kfree(fh);
if (IS_ERR_OR_NULL(upper))
return upper ?: ERR_PTR(-ESTALE);
if (!d_is_dir(upper)) {
pr_warn_ratelimited("overlayfs: invalid index upper (%pd2, upper=%pd2).\n",
index, upper);
dput(upper);
return ERR_PTR(-EIO);
}
return upper;
}
/* Is this a leftover from create/whiteout of directory index entry? */
static bool ovl_is_temp_index(struct dentry *index)
{
return index->d_name.name[0] == '#';
}
/*
* Verify that an index entry name matches the origin file handle stored in
* OVL_XATTR_ORIGIN and that origin file handle can be decoded to lower path.
* Return 0 on match, -ESTALE on mismatch or stale origin, < 0 on error.
*/
int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index)
{
struct ovl_fh *fh = NULL;
size_t len;
struct ovl_path origin = { };
struct ovl_path *stack = &origin;
struct dentry *upper = NULL;
int err;
if (!d_inode(index))
return 0;
/* Cleanup leftover from index create/cleanup attempt */
err = -ESTALE;
if (ovl_is_temp_index(index))
goto fail;
err = -EINVAL;
if (index->d_name.len < sizeof(struct ovl_fh)*2)
goto fail;
err = -ENOMEM;
len = index->d_name.len / 2;
fh = kzalloc(len, GFP_KERNEL);
if (!fh)
goto fail;
err = -EINVAL;
if (hex2bin((u8 *)fh, index->d_name.name, len))
goto fail;
err = ovl_check_fh_len(fh, len);
if (err)
goto fail;
/*
* Whiteout index entries are used as an indication that an exported
* overlay file handle should be treated as stale (i.e. after unlink
* of the overlay inode). These entries contain no origin xattr.
*/
if (ovl_is_whiteout(index))
goto out;
/*
* Verifying directory index entries are not stale is expensive, so
* only verify stale dir index if NFS export is enabled.
*/
if (d_is_dir(index) && !ofs->config.nfs_export)
goto out;
/*
* Directory index entries should have 'upper' xattr pointing to the
* real upper dir. Non-dir index entries are hardlinks to the upper
* real inode. For non-dir index, we can read the copy up origin xattr
* directly from the index dentry, but for dir index we first need to
* decode the upper directory.
*/
upper = ovl_index_upper(ofs, index);
if (IS_ERR_OR_NULL(upper)) {
err = PTR_ERR(upper);
/*
* Directory index entries with no 'upper' xattr need to be
* removed. When dir index entry has a stale 'upper' xattr,
* we assume that upper dir was removed and we treat the dir
* index as orphan entry that needs to be whited out.
*/
if (err == -ESTALE)
goto orphan;
else if (!err)
err = -ESTALE;
goto fail;
}
err = ovl_verify_fh(upper, OVL_XATTR_ORIGIN, fh);
dput(upper);
if (err)
goto fail;
/* Check if non-dir index is orphan and don't warn before cleaning it */
if (!d_is_dir(index) && d_inode(index)->i_nlink == 1) {
err = ovl_check_origin_fh(ofs, fh, index, &stack);
if (err)
goto fail;
if (ovl_get_nlink(origin.dentry, index, 0) == 0)
goto orphan;
}
out:
dput(origin.dentry);
kfree(fh);
return err;
fail:
pr_warn_ratelimited("overlayfs: failed to verify index (%pd2, ftype=%x, err=%i)\n",
index, d_inode(index)->i_mode & S_IFMT, err);
goto out;
orphan:
pr_warn_ratelimited("overlayfs: orphan index entry (%pd2, ftype=%x, nlink=%u)\n",
index, d_inode(index)->i_mode & S_IFMT,
d_inode(index)->i_nlink);
err = -ENOENT;
goto out;
}
static int ovl_get_index_name_fh(struct ovl_fh *fh, struct qstr *name)
{
char *n, *s;
n = kzalloc(fh->len * 2, GFP_KERNEL);
if (!n)
return -ENOMEM;
s = bin2hex(n, fh, fh->len);
*name = (struct qstr) QSTR_INIT(n, s - n);
return 0;
}
/*
* Lookup in indexdir for the index entry of a lower real inode or a copy up
* origin inode. The index entry name is the hex representation of the lower
* inode file handle.
*
* If the index dentry in negative, then either no lower aliases have been
* copied up yet, or aliases have been copied up in older kernels and are
* not indexed.
*
* If the index dentry for a copy up origin inode is positive, but points
* to an inode different than the upper inode, then either the upper inode
* has been copied up and not indexed or it was indexed, but since then
* index dir was cleared. Either way, that index cannot be used to indentify
* the overlay inode.
*/
int ovl_get_index_name(struct dentry *origin, struct qstr *name)
{
struct ovl_fh *fh;
int err;
fh = ovl_encode_fh(origin, false);
if (IS_ERR(fh))
return PTR_ERR(fh);
err = ovl_get_index_name_fh(fh, name);
kfree(fh);
return err;
}
/* Lookup index by file handle for NFS export */
struct dentry *ovl_get_index_fh(struct ovl_fs *ofs, struct ovl_fh *fh)
{
struct dentry *index;
struct qstr name;
int err;
err = ovl_get_index_name_fh(fh, &name);
if (err)
return ERR_PTR(err);
index = lookup_one_len_unlocked(name.name, ofs->indexdir, name.len);
kfree(name.name);
if (IS_ERR(index)) {
if (PTR_ERR(index) == -ENOENT)
index = NULL;
return index;
}
if (d_is_negative(index))
err = 0;
else if (ovl_is_whiteout(index))
err = -ESTALE;
else if (ovl_dentry_weird(index))
err = -EIO;
else
return index;
dput(index);
return ERR_PTR(err);
}
struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper,
struct dentry *origin, bool verify)
{
struct dentry *index;
struct inode *inode;
struct qstr name;
bool is_dir = d_is_dir(origin);
int err;
err = ovl_get_index_name(origin, &name);
if (err)
return ERR_PTR(err);
index = lookup_one_len_unlocked(name.name, ofs->indexdir, name.len);
if (IS_ERR(index)) {
err = PTR_ERR(index);
if (err == -ENOENT) {
index = NULL;
goto out;
}
pr_warn_ratelimited("overlayfs: failed inode index lookup (ino=%lu, key=%*s, err=%i);\n"
"overlayfs: mount with '-o index=off' to disable inodes index.\n",
d_inode(origin)->i_ino, name.len, name.name,
err);
goto out;
}
inode = d_inode(index);
if (d_is_negative(index)) {
goto out_dput;
} else if (ovl_is_whiteout(index) && !verify) {
/*
* When index lookup is called with !verify for decoding an
* overlay file handle, a whiteout index implies that decode
* should treat file handle as stale and no need to print a
* warning about it.
*/
dput(index);
index = ERR_PTR(-ESTALE);
goto out;
} else if (ovl_dentry_weird(index) || ovl_is_whiteout(index) ||
((inode->i_mode ^ d_inode(origin)->i_mode) & S_IFMT)) {
/*
* Index should always be of the same file type as origin
* except for the case of a whiteout index. A whiteout
* index should only exist if all lower aliases have been
* unlinked, which means that finding a lower origin on lookup
* whose index is a whiteout should be treated as an error.
*/
pr_warn_ratelimited("overlayfs: bad index found (index=%pd2, ftype=%x, origin ftype=%x).\n",
index, d_inode(index)->i_mode & S_IFMT,
d_inode(origin)->i_mode & S_IFMT);
goto fail;
} else if (is_dir && verify) {
if (!upper) {
pr_warn_ratelimited("overlayfs: suspected uncovered redirected dir found (origin=%pd2, index=%pd2).\n",
origin, index);
goto fail;
}
/* Verify that dir index 'upper' xattr points to upper dir */
err = ovl_verify_upper(index, upper, false);
if (err) {
if (err == -ESTALE) {
pr_warn_ratelimited("overlayfs: suspected multiply redirected dir found (upper=%pd2, origin=%pd2, index=%pd2).\n",
upper, origin, index);
}
goto fail;
}
} else if (upper && d_inode(upper) != inode) {
goto out_dput;
}
out:
kfree(name.name);
return index;
out_dput:
dput(index);
index = NULL;
goto out;
fail:
dput(index);
index = ERR_PTR(-EIO);
goto out;
}
/*
* Returns next layer in stack starting from top.
* Returns -1 if this is the last layer.
*/
int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
{
struct ovl_entry *oe = dentry->d_fsdata;
BUG_ON(idx < 0);
if (idx == 0) {
ovl_path_upper(dentry, path);
if (path->dentry)
return oe->numlower ? 1 : -1;
idx++;
}
BUG_ON(idx > oe->numlower);
path->dentry = oe->lowerstack[idx - 1].dentry;
path->mnt = oe->lowerstack[idx - 1].layer->mnt;
return (idx < oe->numlower) ? idx + 1 : -1;
}
/* Fix missing 'origin' xattr */
static int ovl_fix_origin(struct dentry *dentry, struct dentry *lower,
struct dentry *upper)
{
int err;
if (ovl_check_origin_xattr(upper))
return 0;
err = ovl_want_write(dentry);
if (err)
return err;
err = ovl_set_origin(dentry, lower, upper);
if (!err)
err = ovl_set_impure(dentry->d_parent, upper->d_parent);
ovl_drop_write(dentry);
return err;
}
struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
struct ovl_entry *oe;
const struct cred *old_cred;
struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
struct ovl_entry *poe = dentry->d_parent->d_fsdata;
struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata;
struct ovl_path *stack = NULL;
struct dentry *upperdir, *upperdentry = NULL;
struct dentry *origin = NULL;
struct dentry *index = NULL;
unsigned int ctr = 0;
struct inode *inode = NULL;
bool upperopaque = false;
char *upperredirect = NULL;
struct dentry *this;
unsigned int i;
int err;
struct ovl_lookup_data d = {
.name = dentry->d_name,
.is_dir = false,
.opaque = false,
.stop = false,
.last = !poe->numlower,
.redirect = NULL,
};
if (dentry->d_name.len > ofs->namelen)
return ERR_PTR(-ENAMETOOLONG);
old_cred = ovl_override_creds(dentry->d_sb);
upperdir = ovl_dentry_upper(dentry->d_parent);
if (upperdir) {
err = ovl_lookup_layer(upperdir, &d, &upperdentry);
if (err)
goto out;
if (upperdentry && unlikely(ovl_dentry_remote(upperdentry))) {
dput(upperdentry);
err = -EREMOTE;
goto out;
}
if (upperdentry && !d.is_dir) {
BUG_ON(!d.stop || d.redirect);
/*
* Lookup copy up origin by decoding origin file handle.
* We may get a disconnected dentry, which is fine,
* because we only need to hold the origin inode in
* cache and use its inode number. We may even get a
* connected dentry, that is not under any of the lower
* layers root. That is also fine for using it's inode
* number - it's the same as if we held a reference
* to a dentry in lower layer that was moved under us.
*/
err = ovl_check_origin(ofs, upperdentry, &stack, &ctr);
if (err)
goto out_put_upper;
}
if (d.redirect) {
err = -ENOMEM;
upperredirect = kstrdup(d.redirect, GFP_KERNEL);
if (!upperredirect)
goto out_put_upper;
if (d.redirect[0] == '/')
poe = roe;
}
upperopaque = d.opaque;
}
if (!d.stop && poe->numlower) {
err = -ENOMEM;
stack = kcalloc(ofs->numlower, sizeof(struct ovl_path),
GFP_KERNEL);
if (!stack)
goto out_put_upper;
}
for (i = 0; !d.stop && i < poe->numlower; i++) {
struct ovl_path lower = poe->lowerstack[i];
d.last = i == poe->numlower - 1;
err = ovl_lookup_layer(lower.dentry, &d, &this);
if (err)
goto out_put;
if (!this)
continue;
/*
* If no origin fh is stored in upper of a merge dir, store fh
* of lower dir and set upper parent "impure".
*/
if (upperdentry && !ctr && !ofs->noxattr) {
err = ovl_fix_origin(dentry, this, upperdentry);
if (err) {
dput(this);
goto out_put;
}
}
/*
* When "verify_lower" feature is enabled, do not merge with a
* lower dir that does not match a stored origin xattr. In any
* case, only verified origin is used for index lookup.
*/
if (upperdentry && !ctr && ovl_verify_lower(dentry->d_sb)) {
err = ovl_verify_origin(upperdentry, this, false);
if (err) {
dput(this);
break;
}
/* Bless lower dir as verified origin */
origin = this;
}
stack[ctr].dentry = this;
stack[ctr].layer = lower.layer;
ctr++;
/*
* Following redirects can have security consequences: it's like
* a symlink into the lower layer without the permission checks.
* This is only a problem if the upper layer is untrusted (e.g
* comes from an USB drive). This can allow a non-readable file
* or directory to become readable.
*
* Only following redirects when redirects are enabled disables
* this attack vector when not necessary.
*/
err = -EPERM;
if (d.redirect && !ofs->config.redirect_follow) {
pr_warn_ratelimited("overlayfs: refusing to follow redirect for (%pd2)\n",
dentry);
goto out_put;
}
if (d.stop)
break;
if (d.redirect && d.redirect[0] == '/' && poe != roe) {
poe = roe;
/* Find the current layer on the root dentry */
i = lower.layer->idx - 1;
}
}
/*
* Lookup index by lower inode and verify it matches upper inode.
* We only trust dir index if we verified that lower dir matches
* origin, otherwise dir index entries may be inconsistent and we
* ignore them. Always lookup index of non-dir and non-upper.
*/
if (ctr && (!upperdentry || !d.is_dir))
origin = stack[0].dentry;
if (origin && ovl_indexdir(dentry->d_sb) &&
(!d.is_dir || ovl_index_all(dentry->d_sb))) {
index = ovl_lookup_index(ofs, upperdentry, origin, true);
if (IS_ERR(index)) {
err = PTR_ERR(index);
index = NULL;
goto out_put;
}
}
oe = ovl_alloc_entry(ctr);
err = -ENOMEM;
if (!oe)
goto out_put;
memcpy(oe->lowerstack, stack, sizeof(struct ovl_path) * ctr);
dentry->d_fsdata = oe;
if (upperopaque)
ovl_dentry_set_opaque(dentry);
if (upperdentry)
ovl_dentry_set_upper_alias(dentry);
else if (index)
upperdentry = dget(index);
if (upperdentry || ctr) {
if (ctr)
origin = stack[0].dentry;
inode = ovl_get_inode(dentry->d_sb, upperdentry, origin, index,
ctr);
err = PTR_ERR(inode);
if (IS_ERR(inode))
goto out_free_oe;
OVL_I(inode)->redirect = upperredirect;
if (index)
ovl_set_flag(OVL_INDEX, inode);
}
revert_creds(old_cred);
dput(index);
kfree(stack);
kfree(d.redirect);
return d_splice_alias(inode, dentry);
out_free_oe:
dentry->d_fsdata = NULL;
kfree(oe);
out_put:
dput(index);
for (i = 0; i < ctr; i++)
dput(stack[i].dentry);
kfree(stack);
out_put_upper:
dput(upperdentry);
kfree(upperredirect);
out:
kfree(d.redirect);
revert_creds(old_cred);
return ERR_PTR(err);
}
bool ovl_lower_positive(struct dentry *dentry)
{
struct ovl_entry *poe = dentry->d_parent->d_fsdata;
const struct qstr *name = &dentry->d_name;
const struct cred *old_cred;
unsigned int i;
bool positive = false;
bool done = false;
/*
* If dentry is negative, then lower is positive iff this is a
* whiteout.
*/
if (!dentry->d_inode)
return ovl_dentry_is_opaque(dentry);
/* Negative upper -> positive lower */
if (!ovl_dentry_upper(dentry))
return true;
old_cred = ovl_override_creds(dentry->d_sb);
/* Positive upper -> have to look up lower to see whether it exists */
for (i = 0; !done && !positive && i < poe->numlower; i++) {
struct dentry *this;
struct dentry *lowerdir = poe->lowerstack[i].dentry;
this = lookup_one_len_unlocked(name->name, lowerdir,
name->len);
if (IS_ERR(this)) {
switch (PTR_ERR(this)) {
case -ENOENT:
case -ENAMETOOLONG:
break;
default:
/*
* Assume something is there, we just couldn't
* access it.
*/
positive = true;
break;
}
} else {
if (this->d_inode) {
positive = !ovl_is_whiteout(this);
done = true;
}
dput(this);
}
}
revert_creds(old_cred);
return positive;
}