linux-kernel - [PATCH 5.7 015/112] tipc: Fix NULL pointer dereference in __tipc

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Date:   Tue,  7 Jul 2020 17:16:20 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+8eac6d030e7807c21d32@...kaller.appspotmail.com,
        YueHaibing <yuehaibing@...wei.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.7 015/112] tipc: Fix NULL pointer dereference in __tipc_sendstream()

From: YueHaibing <yuehaibing@...wei.com>

[ 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@...kaller.appspotmail.com
Fixes: 0a3e060f340d ("tipc: add test for Nagle algorithm effectiveness")
Signed-off-by: YueHaibing <yuehaibing@...wei.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/tipc/socket.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 62fc871a8d673..f02f2abf6e3c0 100644
--- 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;
 			}
-- 
2.25.1