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authorMiklos Szeredi <mszeredi@redhat.com>2016-03-21 17:31:44 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-07-27 09:47:40 -0700
commitdbf72a4d4531e7e5fb28e76d902d66f05c1bfe12 (patch)
treec19301388d1a4349958bb8a67fe6f081fe409e38
parent38da63ef2c131593ff89372048c14cd8bd1fe4b4 (diff)
ovl: verify upper dentry before unlink and rename
commit 11f3710417d026ea2f4fcf362d866342c5274185 upstream. Unlink and rename in overlayfs checked the upper dentry for staleness by verifying upper->d_parent against upperdir. However the dentry can go stale also by being unhashed, for example. Expand the verification to actually look up the name again (under parent lock) and check if it matches the upper dentry. This matches what the VFS does before passing the dentry to filesytem's unlink/rename methods, which excludes any inconsistency caused by overlayfs. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/overlayfs/dir.c59
1 files changed, 38 insertions, 21 deletions
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 977236a46aa2..ba5ef733951f 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -590,21 +590,25 @@ static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
{
struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
struct inode *dir = upperdir->d_inode;
- struct dentry *upper = ovl_dentry_upper(dentry);
+ struct dentry *upper;
int err;
mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
+ upper = lookup_one_len(dentry->d_name.name, upperdir,
+ dentry->d_name.len);
+ err = PTR_ERR(upper);
+ if (IS_ERR(upper))
+ goto out_unlock;
+
err = -ESTALE;
- if (upper->d_parent == upperdir) {
- /* Don't let d_delete() think it can reset d_inode */
- dget(upper);
+ if (upper == ovl_dentry_upper(dentry)) {
if (is_dir)
err = vfs_rmdir(dir, upper);
else
err = vfs_unlink(dir, upper, NULL);
- dput(upper);
ovl_dentry_version_inc(dentry->d_parent);
}
+ dput(upper);
/*
* Keeping this dentry hashed would mean having to release
@@ -614,6 +618,7 @@ static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
*/
if (!err)
d_drop(dentry);
+out_unlock:
mutex_unlock(&dir->i_mutex);
return err;
@@ -834,29 +839,39 @@ static int ovl_rename2(struct inode *olddir, struct dentry *old,
trap = lock_rename(new_upperdir, old_upperdir);
- olddentry = ovl_dentry_upper(old);
- newdentry = ovl_dentry_upper(new);
- if (newdentry) {
+
+ olddentry = lookup_one_len(old->d_name.name, old_upperdir,
+ old->d_name.len);
+ err = PTR_ERR(olddentry);
+ if (IS_ERR(olddentry))
+ goto out_unlock;
+
+ err = -ESTALE;
+ if (olddentry != ovl_dentry_upper(old))
+ goto out_dput_old;
+
+ newdentry = lookup_one_len(new->d_name.name, new_upperdir,
+ new->d_name.len);
+ err = PTR_ERR(newdentry);
+ if (IS_ERR(newdentry))
+ goto out_dput_old;
+
+ err = -ESTALE;
+ if (ovl_dentry_upper(new)) {
if (opaquedir) {
- newdentry = opaquedir;
- opaquedir = NULL;
+ if (newdentry != opaquedir)
+ goto out_dput;
} else {
- dget(newdentry);
+ if (newdentry != ovl_dentry_upper(new))
+ goto out_dput;
}
} else {
new_create = true;
- newdentry = lookup_one_len(new->d_name.name, new_upperdir,
- new->d_name.len);
- err = PTR_ERR(newdentry);
- if (IS_ERR(newdentry))
- goto out_unlock;
+ if (!d_is_negative(newdentry) &&
+ (!new_opaque || !ovl_is_whiteout(newdentry)))
+ goto out_dput;
}
- err = -ESTALE;
- if (olddentry->d_parent != old_upperdir)
- goto out_dput;
- if (newdentry->d_parent != new_upperdir)
- goto out_dput;
if (olddentry == trap)
goto out_dput;
if (newdentry == trap)
@@ -919,6 +934,8 @@ static int ovl_rename2(struct inode *olddir, struct dentry *old,
out_dput:
dput(newdentry);
+out_dput_old:
+ dput(olddentry);
out_unlock:
unlock_rename(new_upperdir, old_upperdir);
out_revert_creds: