From: Paolo Abeni <[email protected]> This is strictly related to commit fb7a0d334894 ("mptcp: ensure snd_nxt is properly initialized on connect"). It turns out that syzkaller can trigger the retransmit after fallback and before processing any other incoming packet - so that snd_una is still left uninitialized.
Address the issue explicitly initializing snd_una together with snd_nxt and write_seq. Suggested-by: Mat Martineau <[email protected]> Fixes: 8fd738049ac3 ("mptcp: fallback in case of simultaneous connect") Cc: [email protected] Reported-by: Christoph Paasch <[email protected]> Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/485 Signed-off-by: Paolo Abeni <[email protected]> Reviewed-by: Mat Martineau <[email protected]> Signed-off-by: Matthieu Baerts (NGI0) <[email protected]> --- net/mptcp/protocol.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 96b113854bd3..bb7dca8aa2d9 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -3740,6 +3740,7 @@ static int mptcp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len) WRITE_ONCE(msk->write_seq, subflow->idsn); WRITE_ONCE(msk->snd_nxt, subflow->idsn); + WRITE_ONCE(msk->snd_una, subflow->idsn); if (likely(!__mptcp_check_fallback(msk))) MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEACTIVE); -- 2.43.0
