netdev - [PATCH net-next] mptcp: fix deadlock in mptcp

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Date:   Thu, 5 May 2022 14:03:03 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Geliang Tang <geliang.tang@...e.com>
Cc:     Matthieu Baerts <matthieu.baerts@...sares.net>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        mptcp@...ts.linux.dev, kernel-janitors@...r.kernel.org
Subject: [PATCH net-next] mptcp: fix deadlock in mptcp_close()

The mptcp_data_lock/unlock(sk) functions are taking the same spin lock
as the lock_sock()/release_sock() functions.  So we're already holding
the lock at this point and taking it again will lead to a deadlock.

Fixes: 4293248c6704 ("mptcp: add data lock for sk timers")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
>From static analysis.  Not tested.

 net/mptcp/protocol.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index a5d466e6b538..eef4673dae3a 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2872,9 +2872,7 @@ static void mptcp_close(struct sock *sk, long timeout)
 		__mptcp_destroy_sock(sk);
 		do_cancel_work = true;
 	} else {
-		mptcp_data_lock(sk);
 		sk_reset_timer(sk, &sk->sk_timer, jiffies + TCP_TIMEWAIT_LEN);
-		mptcp_data_unlock(sk);
 	}
 	release_sock(sk);
 	if (do_cancel_work)
-- 
2.35.1