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

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

[Florian Westphal]

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

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

[Paolo Abeni]

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

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

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

[Jakub Kicinski]

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@redhat.com>
> > Cc: Davide Caratti <dcaratti@redhat.com>
> > Signed-off-by: Florian Westphal <fw@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  
> 
> LGTM, thanks!
> Acked-by: Paolo Abeni <pabeni@redhat.com>

Applied, thanks!