ovl: fail ovl_lock_rename_workdir() if either target is unhashed

As well as checking that the parent hasn't changed after getting the
lock we need to check that the dentry hasn't been unhashed.
Otherwise we might try to rename something that has been removed.

Reported-by: [email protected]
Fixes: d2c9955 ("ovl: Call ovl_create_temp() without lock held.")
Signed-off-by: NeilBrown <[email protected]>
Link: https://patch.msgid.link/[email protected]
Tested-by: [email protected]
Reviewed-by: Amir Goldstein <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

Author: neilbrown

fs/overlayfs/util.c

@@ -1234,9 +1234,9 @@ int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *work,
 		goto err;
 	if (trap)
 		goto err_unlock;
-	if (work && work->d_parent != workdir)
+	if (work && (work->d_parent != workdir || d_unhashed(work)))
 		goto err_unlock;
-	if (upper && upper->d_parent != upperdir)
+	if (upper && (upper->d_parent != upperdir || d_unhashed(upper)))
 		goto err_unlock;
 
 	return 0;