From 967ade52834309a4bf19f2f16403407ba3e30041 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Thu, 26 Nov 2015 08:18:14 -0800
Subject: [PATCH] tcp: initialize tp->copied_seq in case of cross SYN
connection
[ Upstream commit 142a2e7ece8d8ac0e818eb2c91f99ca894730e2a ]
Dmitry provided a syzkaller (http://github.com/google/syzkaller)
generated program that triggers the WARNING at
net/ipv4/tcp.c:1729 in tcp_recvmsg() :
WARN_ON(tp->copied_seq != tp->rcv_nxt &&
!(flags & (MSG_PEEK | MSG_TRUNC)));
His program is specifically attempting a Cross SYN TCP exchange,
that we support (for the pleasure of hackers ?), but it looks we
lack proper tcp->copied_seq initialization.
Thanks again Dmitry for your report and testings.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/tcp_input.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 7b1fc955b6b6..87463c814896 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5638,6 +5638,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
}
tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
+ tp->copied_seq = tp->rcv_nxt;
tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
/* RFC1323: The window in SYN & SYN/ACK segments is
--
2.30.9