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Date:   Wed, 2 Nov 2022 21:28:11 +0800
From:   Lu Wei <>
To:     <>, <>,
        <>, <>, <>,
        <>, <>,
        <>, <>
Subject: [patch net v3] tcp: prohibit TCP_REPAIR_OPTIONS if data was already sent

If setsockopt with option name of TCP_REPAIR_OPTIONS and opt_code
of TCPOPT_SACK_PERM is called to enable sack after data is sent
and before data is acked, it will trigger a warning in function
tcp_verify_left_out() as follows:

WARNING: CPU: 8 PID: 0 at net/ipv4/tcp_input.c:2132

The warning is caused in the following steps:
1. a socket named socketA is created
2. socketA enters repair mode without build a connection
3. socketA calls connect() and its state is changed to TCP_ESTABLISHED
4. socketA leaves repair mode
5. socketA calls sendmsg() to send data, packets_out and sack_outs(dup
   ack receives) increase
6. socketA enters repair mode again
7. socketA calls setsockopt with TCPOPT_SACK_PERM to enable sack
8. retransmit timer expires, it calls tcp_timeout_mark_lost(), lost_out
9. sack_outs + lost_out > packets_out triggers since lost_out and
   sack_outs increase repeatly

In function tcp_timeout_mark_lost(), tp->sacked_out will be cleared if
Step7 not happen and the warning will not be triggered. As suggested by
Denis and Eric, TCP_REPAIR_OPTIONS should be prohibited if data was
already sent. So this patch checks tp->segs_out, only TCP_REPAIR_OPTIONS
can be set only if tp->segs_out is 0.

socket-tcp tests in CRIU has been tested as follows:
$ sudo ./test/ run -t zdtm/static/socket-tcp*  --keep-going \

socket-tcp* represent all socket-tcp tests in test/zdtm/static/.

Fixes: b139ba4e90dc ("tcp: Repair connection-time negotiated parameters")
Signed-off-by: Lu Wei <>
 net/ipv4/tcp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index ef14efa1fb70..1f5cc32cf0cc 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3647,7 +3647,7 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
 		if (!tp->repair)
 			err = -EINVAL;
-		else if (sk->sk_state == TCP_ESTABLISHED)
+		else if (sk->sk_state == TCP_ESTABLISHED && !tp->segs_out)
 			err = tcp_repair_options_est(sk, optval, optlen);
 			err = -EPERM;

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