ext4: fix buffer leak in __ext4_read_dirblock() on error path

BugLink: https://bugs.launchpad.net/bugs/1810947

commit de59fae0 upstream.

Fixes: dc6982ff ("ext4: refactor code to read directory blocks ...")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org # 3.9
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

fs/ext4/namei.c

@@ -124,6 +124,7 @@ static struct buffer_head *__ext4_read_dirblock(struct inode *inode,
 	if (!is_dx_block && type == INDEX) {
 		ext4_error_inode(inode, func, line, block,
 		       "directory leaf block found instead of index block");
+		brelse(bh);
 		return ERR_PTR(-EFSCORRUPTED);
 	}
 	if (!ext4_has_metadata_csum(inode->i_sb) ||