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

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Date:   Tue, 24 Nov 2020 17:42:21 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     Florian Westphal <fw@...len.de>, netdev@...r.kernel.org
Cc:     mptcp@...ts.01.org, Davide Caratti <dcaratti@...hat.com>
Subject: Re: [PATCH net-next] mptcp: put reference in mptcp timeout timer

On Tue, 2020-11-24 at 17:24 +0100, Florian Westphal wrote:
> 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.

Whoops, my fault!

> 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

LGTM, thanks!
Acked-by: Paolo Abeni <pabeni@...hat.com>