On close this timer might be scheduled. mptcp uses sk_reset_timer for this, so the a reference on the mptcp socket is taken.
This causes a refcount leak which can for example be reproduced with 'mp_join_server_v4.pkt' from the mptcp-packetdrill repo. The leak has nothing to do with join requests, v1_mp_capable_bind_no_cs.pkt works too when replacing the last ack mpcapable to v1 instead of v0. unreferenced object 0xffff888109bba040 (size 2744): comm "packetdrill", [..] backtrace: [..] sk_prot_alloc.isra.0+0x2b/0xc0 [..] sk_clone_lock+0x2f/0x740 [..] mptcp_sk_clone+0x33/0x1a0 [..] subflow_syn_recv_sock+0x2b1/0x690 [..] Fixes: e16163b6e2b7 ("mptcp: refactor shutdown and close") Cc: Paolo Abeni <pab...@redhat.com> Cc: Davide Caratti <dcara...@redhat.com> Signed-off-by: Florian Westphal <f...@strlen.de> --- net/mptcp/protocol.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 4b7794835fea..dc979571f561 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -1710,6 +1710,7 @@ static void mptcp_timeout_timer(struct timer_list *t) struct sock *sk = from_timer(sk, t, sk_timer); mptcp_schedule_work(sk); + sock_put(sk); } /* Find an idle subflow. Return NULL if there is unacked data at tcp -- 2.26.2