ocfs2: fix double free in user_cluster_connect()

user_cluster_disconnect() frees "conn->cc_private" which is "lc" but then
the error handling frees "lc" a second time.  Set "lc" to NULL on this
path to avoid a double free.

Link: https://lkml.kernel.org/r/aNKDz_7JF7aycZ0k@stanley.mountain
Fixes: c994c2e ("ocfs2: use the new DLM operation callbacks while requesting new lockspace")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-by: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Dan Carpenter

fs/ocfs2/stack_user.c

@@ -1011,6 +1011,7 @@ static int user_cluster_connect(struct ocfs2_cluster_connection *conn)
 			printk(KERN_ERR "ocfs2: Could not determine"
 					" locking version\n");
 			user_cluster_disconnect(conn);
+			lc = NULL;
 			goto out;
 		}
 		wait_event(lc->oc_wait, (atomic_read(&lc->oc_this_node) > 0));