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

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Date:   Wed, 25 Nov 2020 12:33:20 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     Florian Westphal <fw@...len.de>, netdev@...r.kernel.org,
        mptcp@...ts.01.org, Davide Caratti <dcaratti@...hat.com>
Subject: Re: [PATCH net-next] mptcp: put reference in mptcp timeout timer

On Tue, 24 Nov 2020 17:42:21 +0100 Paolo Abeni wrote:
> 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>

Applied, thanks!