ubifs: Fix memory leak in read_znode() error path

In read_znode(), the indexing node 'idx' is allocated by kmalloc().
However, it is not deallocated in the following execution if
ubifs_node_check_hash() fails, leading to a memory leak bug. To fix this
issue, free 'idx' before returning the error.

Fixes: 16a26b20 ("ubifs: authentication: Add hashes to index nodes")
Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
Signed-off-by: Richard Weinberger <richard@nod.at>

fs/ubifs/tnc_misc.c

@@ -284,6 +284,7 @@ static int read_znode(struct ubifs_info *c, struct ubifs_zbranch *zzbr,
 	err = ubifs_node_check_hash(c, idx, zzbr->hash);
 	if (err) {
 		ubifs_bad_hash(c, idx, zzbr->hash, lnum, offs);
+		kfree(idx);
 		return err;
 	}