[PATCH v1] fs:dlm:Fix NULL pointer dereference bug in accept_from_sock()

[Wang Ming]

newcon -> sock is NULL but dereferenced.
First check newcon. Whether sock is a null pointer.
If so, the subsequent operations are skipped.
If it is not empty, perform subsequent operations.

Signed-off-by: Wang Ming <machel@xxxxxxxx>
---
 fs/dlm/lowcomms.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index 9f14ea9f6..ea18b9478 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -1081,9 +1081,12 @@ static int accept_from_sock(void)
 		add_sock(newsock, newcon);
 
 		/* check if we receved something while adding */
-		lock_sock(newcon->sock->sk);
-		lowcomms_queue_rwork(newcon);
-		release_sock(newcon->sock->sk);
+		if (newcon->sock) {
+			lock_sock(newcon->sock->sk);
+			lowcomms_queue_rwork(newcon);
+			release_sock(newcon->sock->sk);
+		}
+
 	}
 	up_write(&newcon->sock_lock);
 	srcu_read_unlock(&connections_srcu, idx);
-- 
2.25.1