md-cluster: init suspend_list and suspend_lock early in join

GuoqingJiang · NeilBrown · commit 9e3072e37332 · 2015-08-31T19:42:05.000+02:00
If the node just join the cluster, and receive the msg from other nodes
before init suspend_list, it will cause kernel crash due to NULL pointer
dereference, so move the initializations early to fix the bug.

md-cluster: Joined cluster 3578507b-e0cb-6d4f-6322-696cd7b1b10c slot 3
BUG: unable to handle kernel NULL pointer dereference at           (null)
... ... ...
Call Trace:
[&lt;ffffffffa0444924&gt;] process_recvd_msg+0x2e4/0x330 [md_cluster]
[&lt;ffffffffa0444a06&gt;] recv_daemon+0x96/0x170 [md_cluster]
[&lt;ffffffffa045189d&gt;] md_thread+0x11d/0x170 [md_mod]
[&lt;ffffffff810768c4&gt;] kthread+0xb4/0xc0
[&lt;ffffffff8151927c&gt;] ret_from_fork+0x7c/0xb0
... ... ...
RIP  [&lt;ffffffffa0443581&gt;] __remove_suspend_info+0x11/0xa0 [md_cluster]

Reviewed-by: Goldwyn Rodrigues &lt;rgoldwyn@suse.com&gt;
Signed-off-by: Guoqing Jiang &lt;gqjiang@suse.com&gt;
Signed-off-by: NeilBrown &lt;neilb@suse.com&gt;
diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c
@@ -671,6 +671,8 @@ static int join(struct mddev *mddev, int nodes)
 	if (!cinfo)
 		return -ENOMEM;
 
+	INIT_LIST_HEAD(&cinfo->suspend_list);
+	spin_lock_init(&cinfo->suspend_lock);
 	init_completion(&cinfo->completion);
 
 	mutex_init(&cinfo->sb_mutex);
@@ -736,9 +738,6 @@ static int join(struct mddev *mddev, int nodes)
 		goto err;
 	}
 
-	INIT_LIST_HEAD(&cinfo->suspend_list);
-	spin_lock_init(&cinfo->suspend_lock);
-
 	ret = gather_all_resync_info(mddev, nodes);
 	if (ret)
 		goto err;
