Subject: Re: [PATCH net-next] tcp: Dump bound-only sockets in inet_diag.

From: Guillaume Nault <[email-masked]>
Date: Tue, 26 Sep 2023 12:48:41 +0200

On Fri, Sep 22, 2023 at 10:47:18AM -0700, Kuniyuki Iwashima wrote:
> From: Guillaume Nault <[email-masked]>
> Date: Fri, 22 Sep 2023 18:59:57 +0200
> > Walk the hashinfo->bhash table so that inet_diag can dump TCP sockets
> 
> I think we should use bhash2 as bhash could be long enough for reuseport
> listeners.  That's why bhash2 is introduced.

Okay, I'll try that.

> > that are bound but haven't yet called connect() or listen().
> > 
> > This allows ss to dump bound-only TCP sockets, together with listening
> > sockets (as there's no specific state for bound-only sockets). This is
> > similar to the UDP behaviour for which bound-only sockets are already
> > dumped by ss -lu.
> > 
> > The code is inspired by the ->lhash2 loop. However there's no manual
> > test of the source port, since this kind of filtering is already
> > handled by inet_diag_bc_sk().
> > 
> > No change is needed for ss. With an IPv4, an IPv6 and an IPv6-only
> > socket, bound respectively to 40000, 64000, 60000, the result is:
> > 
> >   $ ss -lt
> >   State  Recv-Q Send-Q Local Address:Port  Peer Address:PortProcess
> >   UNCONN 0      0            0.0.0.0:40000      0.0.0.0:*
> >   UNCONN 0      0               [::]:60000         [::]:*
> >   UNCONN 0      0                  *:64000            *:*
> > 
> > Signed-off-by: Guillaume Nault <[email-masked]>
> > ---
> >  net/ipv4/inet_diag.c | 54 ++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 54 insertions(+)
> > 
> > diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
> > index e13a84433413..de9c0c8cf42b 100644
> > --- a/net/ipv4/inet_diag.c
> > +++ b/net/ipv4/inet_diag.c
> > @@ -1077,6 +1077,60 @@ void inet_diag_dump_icsk(struct inet_hashinfo *hashinfo, struct sk_buff *skb,
> >  		s_i = num = s_num = 0;
> >  	}
> >  
> > +	/* Dump bound-only sockets */
> > +	if (cb->args[0] == 1) {
> > +		if (!(idiag_states & TCPF_CLOSE))
> > +			goto skip_bind_ht;
> > +
> > +		for (i = s_i; i <= hashinfo->bhash_size; i++) {
> > +			struct inet_bind_hashbucket *ibb;
> > +			struct inet_bind_bucket *tb;
> > +
> > +			num = 0;
> > +			ibb = &hashinfo->bhash[i];
> > +
> > +			spin_lock_bh(&ibb->lock);
> > +			inet_bind_bucket_for_each(tb, &ibb->chain) {
> > +				if (!net_eq(ib_net(tb), net))
> > +					continue;
> > +
> > +				sk_for_each_bound(sk, &tb->owners) {
> > +					struct inet_sock *inet = inet_sk(sk);
> > +
> > +					if (num < s_num)
> > +						goto next_bind;
> > +
> > +					if (sk->sk_state != TCP_CLOSE ||
> > +					    !inet->inet_num)
> > +						goto next_bind;
> > +
> > +					if (r->sdiag_family != AF_UNSPEC &&
> > +					    r->sdiag_family != sk->sk_family)
> > +						goto next_bind;
> > +
> > +					if (!inet_diag_bc_sk(bc, sk))
> > +						goto next_bind;
> > +
> > +					if (inet_sk_diag_fill(sk, NULL, skb,
> > +							      cb, r,
> > +							      NLM_F_MULTI,
> > +							      net_admin) < 0) {
> > +						spin_unlock_bh(&ibb->lock);
> > +						goto done;
> > +					}
> > +next_bind:
> > +					num++;
> > +				}
> > +			}
> > +			spin_unlock_bh(&ibb->lock);
> 
> Here we should add cond_resched(), otherwise syzbot could abuse this
> and report hung task.

I'll look into that too. Thanks.

> > +
> > +			s_num = 0;
> > +		}
> > +skip_bind_ht:
> > +		cb->args[0] = 2;
> > +		s_i = num = s_num = 0;
> > +	}
> > +
> >  	if (!(idiag_states & ~TCPF_LISTEN))
> >  		goto out;
> >  
> > -- 
> > 2.39.2
>