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namei.c
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namei.c
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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2011 Novell Inc.
* Copyright (C) 2016 Red Hat, Inc.
*/
#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 super_block *sb;
struct qstr name;
bool is_dir;
bool opaque;
bool stop;
bool last;
char *redirect;
bool metacopy;
};
static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d,
size_t prelen, const char *post)
{
int res;
char *buf;
struct ovl_fs *ofs = OVL_FS(d->sb);
buf = ovl_get_redirect_xattr(ofs, dentry, prelen + strlen(post));
if (IS_ERR_OR_NULL(buf))
return PTR_ERR(buf);
if (buf[0] == '/') {
/*
* One of the ancestor path elements in an absolute path
* lookup in ovl_lookup_layer() could have been opaque and
* that will stop further lookup in lower layers (d->stop=true)
* But we have found an absolute redirect in decendant path
* element and that should force continue lookup in lower
* layers (reset d->stop).
*/
d->stop = false;
} else {
res = strlen(buf) + 1;
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;
}
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_fb_len(struct ovl_fb *fb, int fb_len)
{
if (fb_len < sizeof(struct ovl_fb) || fb_len < fb->len)
return -EINVAL;
if (fb->magic != OVL_FH_MAGIC)
return -EINVAL;
/* Treat larger version and unknown flags as "origin unknown" */
if (fb->version > OVL_FH_VERSION || fb->flags & ~OVL_FH_FLAG_ALL)
return -ENODATA;
/* Treat endianness mismatch as "origin unknown" */
if (!(fb->flags & OVL_FH_FLAG_ANY_ENDIAN) &&
(fb->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN)
return -ENODATA;
return 0;
}
static struct ovl_fh *ovl_get_fh(struct ovl_fs *ofs, struct dentry *dentry,
enum ovl_xattr ox)
{
int res, err;
struct ovl_fh *fh = NULL;
res = ovl_do_getxattr(ofs, dentry, ox, 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 + OVL_FH_WIRE_OFFSET, GFP_KERNEL);
if (!fh)
return ERR_PTR(-ENOMEM);
res = ovl_do_getxattr(ofs, dentry, ox, fh->buf, res);
if (res < 0)
goto fail;
err = ovl_check_fb_len(&fh->fb, res);
if (err < 0) {
if (err == -ENODATA)
goto out;
goto invalid;
}
return fh;
out:
kfree(fh);
return NULL;
fail:
pr_warn_ratelimited("failed to get origin (%i)\n", res);
goto out;
invalid:
pr_warn_ratelimited("invalid origin (%*phN)\n", res, fh);
goto out;
}
struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh,
struct vfsmount *mnt, bool connected)
{
struct dentry *real;
int bytes;
if (!capable(CAP_DAC_READ_SEARCH))
return NULL;
/*
* Make sure that the stored uuid matches the uuid of the lower
* layer where file handle will be decoded.
* In case of uuid=off option just make sure that stored uuid is null.
*/
if (ofs->config.uuid ? !uuid_equal(&fh->fb.uuid, &mnt->mnt_sb->s_uuid) :
!uuid_is_null(&fh->fb.uuid))
return NULL;
bytes = (fh->fb.len - offsetof(struct ovl_fb, fid));
real = exportfs_decode_fh(mnt, (struct fid *)fh->fb.fid,
bytes >> 2, (int)fh->fb.type,
connected ? ovl_acceptable : NULL, 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->fb.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 super_block *sb, struct dentry *dentry)
{
return ovl_check_dir_xattr(sb, dentry, OVL_XATTR_OPAQUE);
}
static struct dentry *ovl_lookup_positive_unlocked(const char *name,
struct dentry *base, int len,
bool drop_negative)
{
struct dentry *ret = lookup_one_len_unlocked(name, base, len);
if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
if (drop_negative && ret->d_lockref.count == 1) {
spin_lock(&ret->d_lock);
/* Recheck condition under lock */
if (d_is_negative(ret) && ret->d_lockref.count == 1)
__d_drop(ret);
spin_unlock(&ret->d_lock);
}
dput(ret);
ret = ERR_PTR(-ENOENT);
}
return ret;
}
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, bool drop_negative)
{
struct dentry *this;
int err;
bool last_element = !post[0];
this = ovl_lookup_positive_unlocked(name, base, namelen, drop_negative);
if (IS_ERR(this)) {
err = PTR_ERR(this);
this = NULL;
if (err == -ENOENT || err == -ENAMETOOLONG)
goto out;
goto out_err;
}
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;
}
/*
* This dentry should be a regular file if previous layer lookup
* found a metacopy dentry.
*/
if (last_element && d->metacopy && !d_is_reg(this)) {
d->stop = true;
goto put_and_out;
}
if (!d_can_lookup(this)) {
if (d->is_dir || !last_element) {
d->stop = true;
goto put_and_out;
}
err = ovl_check_metacopy_xattr(OVL_FS(d->sb), this);
if (err < 0)
goto out_err;
d->metacopy = err;
d->stop = !d->metacopy;
if (!d->metacopy || d->last)
goto out;
} else {
if (ovl_lookup_trap_inode(d->sb, this)) {
/* Caught in a trap of overlapping layers */
err = -ELOOP;
goto out_err;
}
if (last_element)
d->is_dir = true;
if (d->last)
goto out;
if (ovl_is_opaquedir(d->sb, this)) {
d->stop = true;
if (last_element)
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, bool drop_negative)
{
/* 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, drop_negative);
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,
drop_negative);
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, bool connected,
struct dentry *upperdentry, struct ovl_path **stackp)
{
struct dentry *origin = NULL;
int i;
for (i = 1; i < ofs->numlayer; i++) {
/*
* If lower fs uuid is not unique among lower fs we cannot match
* fh->uuid to layer.
*/
if (ofs->layers[i].fsid &&
ofs->layers[i].fs->bad_uuid)
continue;
origin = ovl_decode_real_fh(ofs, fh, ofs->layers[i].mnt,
connected);
if (origin)
break;
}
if (!origin)
return -ESTALE;
else if (IS_ERR(origin))
return PTR_ERR(origin);
if (upperdentry && !ovl_is_whiteout(upperdentry) &&
inode_wrong_type(d_inode(upperdentry), d_inode(origin)->i_mode))
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->layers[i]
};
return 0;
invalid:
pr_warn_ratelimited("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)
{
struct ovl_fh *fh = ovl_get_fh(ofs, upperdentry, OVL_XATTR_ORIGIN);
int err;
if (IS_ERR_OR_NULL(fh))
return PTR_ERR(fh);
err = ovl_check_origin_fh(ofs, fh, false, upperdentry, stackp);
kfree(fh);
if (err) {
if (err == -ESTALE)
return 0;
return err;
}
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 ovl_fs *ofs, struct dentry *dentry,
enum ovl_xattr ox, const struct ovl_fh *fh)
{
struct ovl_fh *ofh = ovl_get_fh(ofs, dentry, ox);
int err = 0;
if (!ofh)
return -ENODATA;
if (IS_ERR(ofh))
return PTR_ERR(ofh);
if (fh->fb.len != ofh->fb.len || memcmp(&fh->fb, &ofh->fb, fh->fb.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 ovl_fs *ofs, struct dentry *dentry,
enum ovl_xattr ox, struct dentry *real, bool is_upper,
bool set)
{
struct inode *inode;
struct ovl_fh *fh;
int err;
fh = ovl_encode_real_fh(ofs, real, is_upper);
err = PTR_ERR(fh);
if (IS_ERR(fh)) {
fh = NULL;
goto fail;
}
err = ovl_verify_fh(ofs, dentry, ox, fh);
if (set && err == -ENODATA)
err = ovl_do_setxattr(ofs, dentry, ox, fh->buf, fh->fb.len);
if (err)
goto fail;
out:
kfree(fh);
return err;
fail:
inode = d_inode(real);
pr_warn_ratelimited("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(ofs, index, OVL_XATTR_UPPER);
if (IS_ERR_OR_NULL(fh))
return ERR_CAST(fh);
upper = ovl_decode_real_fh(ofs, fh, ovl_upper_mnt(ofs), true);
kfree(fh);
if (IS_ERR_OR_NULL(upper))
return upper ?: ERR_PTR(-ESTALE);
if (!d_is_dir(upper)) {
pr_warn_ratelimited("invalid index upper (%pd2, upper=%pd2).\n",
index, upper);
dput(upper);
return ERR_PTR(-EIO);
}
return upper;
}
/*
* 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;
err = -EINVAL;
if (index->d_name.len < sizeof(struct ovl_fb)*2)
goto fail;
err = -ENOMEM;
len = index->d_name.len / 2;
fh = kzalloc(len + OVL_FH_WIRE_OFFSET, GFP_KERNEL);
if (!fh)
goto fail;
err = -EINVAL;
if (hex2bin(fh->buf, index->d_name.name, len))
goto fail;
err = ovl_check_fb_len(&fh->fb, 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(ofs, 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, false, index, &stack);
if (err)
goto fail;
if (ovl_get_nlink(ofs, origin.dentry, index, 0) == 0)
goto orphan;
}
out:
dput(origin.dentry);
kfree(fh);
return err;
fail:
pr_warn_ratelimited("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("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 = kcalloc(fh->fb.len, 2, GFP_KERNEL);
if (!n)
return -ENOMEM;
s = bin2hex(n, fh->buf, fh->fb.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 ovl_fs *ofs, struct dentry *origin,
struct qstr *name)
{
struct ovl_fh *fh;
int err;
fh = ovl_encode_real_fh(ofs, 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_positive_unlocked(name.name, ofs->indexdir, name.len);
kfree(name.name);
if (IS_ERR(index)) {
if (PTR_ERR(index) == -ENOENT)
index = NULL;
return index;
}
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(ofs, origin, &name);
if (err)
return ERR_PTR(err);
index = lookup_positive_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("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 (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_wrong_type(inode, d_inode(origin)->i_mode)) {
/*
* 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("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("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(ofs, index, upper, false);
if (err) {
if (err == -ESTALE) {
pr_warn_ratelimited("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 ovl_fs *ofs, struct dentry *dentry,
struct dentry *lower, struct dentry *upper)
{
int err;
if (ovl_check_origin_xattr(ofs, upper))
return 0;
err = ovl_want_write(dentry);
if (err)
return err;
err = ovl_set_origin(ofs, 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, *origin_path = 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;
bool uppermetacopy = false;
struct ovl_lookup_data d = {
.sb = dentry->d_sb,
.name = dentry->d_name,
.is_dir = false,
.opaque = false,
.stop = false,
.last = ofs->config.redirect_follow ? false : !poe->numlower,
.redirect = NULL,
.metacopy = false,
};
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, true);
if (err)
goto out;
if (upperdentry && upperdentry->d_flags & DCACHE_OP_REAL) {
dput(upperdentry);
err = -EREMOTE;
goto out;
}
if (upperdentry && !d.is_dir) {
/*
* 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, &origin_path);
if (err)
goto out_put_upper;
if (d.metacopy)
uppermetacopy = true;
}
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->numlayer - 1, 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];
if (!ofs->config.redirect_follow)
d.last = i == poe->numlower - 1;
else
d.last = lower.layer->idx == roe->numlower;
err = ovl_lookup_layer(lower.dentry, &d, &this, false);
if (err)
goto out_put;
if (!this)
continue;
if ((uppermetacopy || d.metacopy) && !ofs->config.metacopy) {
dput(this);
err = -EPERM;
pr_warn_ratelimited("refusing to follow metacopy origin for (%pd2)\n", dentry);
goto out_put;
}
/*
* 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 && d.is_dir) {
err = ovl_fix_origin(ofs, 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.
*
* For non-dir dentry, if index=on, then ensure origin
* matches the dentry found using path based lookup,
* otherwise error out.
*/
if (upperdentry && !ctr &&
((d.is_dir && ovl_verify_lower(dentry->d_sb)) ||
(!d.is_dir && ofs->config.index && origin_path))) {
err = ovl_verify_origin(ofs, upperdentry, this, false);
if (err) {
dput(this);
if (d.is_dir)
break;
goto out_put;
}
origin = this;
}
if (d.metacopy && ctr) {
/*
* Do not store intermediate metacopy dentries in
* lower chain, except top most lower metacopy dentry.
* Continue the loop so that if there is an absolute
* redirect on this dentry, poe can be reset to roe.
*/
dput(this);
this = NULL;
} else {
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("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;