Commit c12bbe85 authored by Menglong Dong's avatar Menglong Dong Committed by Zhengchao Shao
Browse files

net: tcp: fix unexcepted socket die when snd_wnd is 0 

stable inclusion
from stable-v4.19.318
commit faa0a1fc2a0bb510b2381a5c7aa5b46e9a83d64a
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAD4B4
CVE: CVE-2024-41007

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=faa0a1fc2a0bb510b2381a5c7aa5b46e9a83d64a

---------------------------

commit e89688e3 upstream.

In tcp_retransmit_timer(), a window shrunk connection will be regarded
as timeout if 'tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX'. This is not
right all the time.

The retransmits will become zero-window probes in tcp_retransmit_timer()
if the 'snd_wnd==0'. Therefore, the icsk->icsk_rto will come up to
TCP_RTO_MAX sooner or later.

However, the timer can be delayed and be triggered after 122877ms, not
TCP_RTO_MAX, as I tested.

Therefore, 'tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX' is always true
once the RTO come up to TCP_RTO_MAX, and the socket will die.

Fix this by replacing the 'tcp_jiffies32' with '(u32)icsk->icsk_timeout',
which is exact the timestamp of the timeout.

However, "tp->rcv_tstamp" can restart from idle, then tp->rcv_tstamp
could already be a long time (minutes or hours) in the past even on the
first RTO. So we double check the timeout with the duration of the
retransmission.

Meanwhile, making "2 * TCP_RTO_MAX" as the timeout to avoid the socket
dying too soon.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Link: https://lore.kernel.org/netdev/CADxym3YyMiO+zMD4zj03YPM3FBi-1LHi6gSD2XT8pyAMM096pg@mail.gmail.com/


Signed-off-by: default avatarMenglong Dong <imagedong@tencent.com>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarZhengchao Shao <shaozhengchao@huawei.com>
parent 1bd568a0

net/ipv4/tcp_timer.c

+17 −1
Original line number Diff line number Diff line
@@ -411,6 +411,22 @@ static void tcp_fastopen_synack_timer(struct sock *sk) 
			  TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX);

}



static bool tcp_rtx_probe0_timed_out(const struct sock *sk,

				     const struct sk_buff *skb)

{

	const struct tcp_sock *tp = tcp_sk(sk);

	const int timeout = TCP_RTO_MAX * 2;

	u32 rcv_delta, rtx_delta;



	rcv_delta = inet_csk(sk)->icsk_timeout - tp->rcv_tstamp;

	if (rcv_delta <= timeout)

		return false;



	rtx_delta = (u32)msecs_to_jiffies(tcp_time_stamp(tp) -

			(tp->retrans_stamp ?: tcp_skb_timestamp(skb)));



	return rtx_delta > timeout;

}



/**

 *  tcp_retransmit_timer() - The TCP retransmit timeout handler
@@ -471,7 +487,7 @@ void tcp_retransmit_timer(struct sock *sk) 
					    tp->snd_una, tp->snd_nxt);

		}

#endif

		if (tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX) {

		if (tcp_rtx_probe0_timed_out(sk, skb)) {

			tcp_write_err(sk);

			goto out;

		}