netdev - [PATCH net-next] mptcp: put reference in mptcp timeout timer

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Date:   Tue, 24 Nov 2020 17:24:46 +0100
From:   Florian Westphal <fw@...len.de>
To:     <netdev@...r.kernel.org>
Cc:     <mptcp@...ts.01.org>, Florian Westphal <fw@...len.de>,
        Paolo Abeni <pabeni@...hat.com>,
        Davide Caratti <dcaratti@...hat.com>
Subject: [PATCH net-next] mptcp: put reference in mptcp timeout timer

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 <pabeni@...hat.com>
Cc: Davide Caratti <dcaratti@...hat.com>
Signed-off-by: Florian Westphal <fw@...len.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