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Date: Wed, 1 Nov 2017 22:26:25 +0100 From: Willy Tarreau <w@....eu> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org, linux@...ck-us.net Cc: Wei Wang <weiwan@...gle.com>, Eric Dumazet <edumazet@...gle.com>, Neal Cardwell <ncardwell@...gle.com>, Yuchung Cheng <ycheng@...gle.com>, "David S . Miller" <davem@...emloft.net>, Willy Tarreau <w@....eu> Subject: [PATCH 3.10 084/139] tcp: initialize rcv_mss to TCP_MIN_MSS instead of 0 From: Wei Wang <weiwan@...gle.com> commit 499350a5a6e7512d9ed369ed63a4244b6536f4f8 upstream. When tcp_disconnect() is called, inet_csk_delack_init() sets icsk->icsk_ack.rcv_mss to 0. This could potentially cause tcp_recvmsg() => tcp_cleanup_rbuf() => __tcp_select_window() call path to have division by 0 issue. So this patch initializes rcv_mss to TCP_MIN_MSS instead of 0. Reported-by: Andrey Konovalov <andreyknvl@...gle.com> Signed-off-by: Wei Wang <weiwan@...gle.com> Signed-off-by: Eric Dumazet <edumazet@...gle.com> Signed-off-by: Neal Cardwell <ncardwell@...gle.com> Signed-off-by: Yuchung Cheng <ycheng@...gle.com> Signed-off-by: David S. Miller <davem@...emloft.net> Signed-off-by: Willy Tarreau <w@....eu> --- net/ipv4/tcp.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 446dc4f..b80b399 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2313,6 +2313,10 @@ int tcp_disconnect(struct sock *sk, int flags) tcp_set_ca_state(sk, TCP_CA_Open); tcp_clear_retrans(tp); inet_csk_delack_init(sk); + /* Initialize rcv_mss to TCP_MIN_MSS to avoid division by 0 + * issue in __tcp_select_window() + */ + icsk->icsk_ack.rcv_mss = TCP_MIN_MSS; tcp_init_send_head(sk); memset(&tp->rx_opt, 0, sizeof(tp->rx_opt)); __sk_dst_reset(sk); -- 2.8.0.rc2.1.gbe9624a
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