ovl: fix BUG_ON() in may_delete() when called from ovl_cleanup()

If function ovl_instantiate() returns an error, ovl_cleanup will be called
and try to remove newdentry from wdir, but the newdentry has been moved to
udir at this time.  This will causes BUG_ON(victim->d_parent->d_inode !=
dir) in fs/namei.c:may_delete.

Signed-off-by: chenying <[email protected]>
Fixes: 01b39dc ("ovl: use inode_insert5() to hash a newly created inode")
Link: https://lore.kernel.org/linux-unionfs/[email protected]/
Cc: <[email protected]> # v4.18
Signed-off-by: Miklos Szeredi <[email protected]>

Author: chenyingk

fs/overlayfs/dir.c

@@ -545,8 +545,10 @@ static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
 			goto out_cleanup;
 	}
 	err = ovl_instantiate(dentry, inode, newdentry, hardlink);
-	if (err)
-		goto out_cleanup;
+	if (err) {
+		ovl_cleanup(udir, newdentry);
+		dput(newdentry);
+	}
 out_dput:
 	dput(upper);
 out_unlock: