tipc: Fix NULL pointer dereference in __tipc_sendstream()

[ Upstream commit 4c21daae3dbc9f8536cc18e6e53627821fa2c90c ]

tipc_sendstream() may send zero length packet, then tipc_msg_append()
do not alloc skb, skb_peek_tail() will get NULL, msg_set_ack_required
will trigger NULL pointer dereference.

Reported-by: syzbot+8eac6d030e7807c21d32@syzkaller.appspotmail.com
Fixes: 0a3e060f340d ("tipc: add test for Nagle algorithm effectiveness")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 62fc871a8d67369afcf6f721d9a2173655af6a52..f02f2abf6e3c03ffbe08febef10206168875797a 100644 (file)
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -1589,8 +1589,12 @@ static int __tipc_sendstream(struct socket *sock, struct msghdr *m, size_t dlen)
                                tsk->pkt_cnt += skb_queue_len(txq);
                        } else {
                                skb = skb_peek_tail(txq);
-                               msg_set_ack_required(buf_msg(skb));
-                               tsk->expect_ack = true;
+                               if (skb) {
+                                       msg_set_ack_required(buf_msg(skb));
+                                       tsk->expect_ack = true;
+                               } else {
+                                       tsk->expect_ack = false;
+                               }
                                tsk->msg_acc = 0;
                                tsk->pkt_cnt = 0;
                        }