Re: [PATCH mptcp] mptcp: remove tcp ulp setsockopt support

[Mat Martineau]

On Mon, 6 Dec 2021, Jakub Kicinski wrote:

> On Mon, 6 Dec 2021 07:53:26 -0800 Jakub Kicinski wrote:
> > On Sun,  5 Dec 2021 20:27:00 +0100 Florian Westphal wrote:
> > > TCP_ULP setsockopt cannot be used for mptcp because its already
> > > used internally to plumb subflow (tcp) sockets to the mptcp layer.
> > >
> > > syzbot managed to trigger a crash for mptcp connections that are
> > > in fallback mode:
> >
> > Fallback mode meaning ops are NULL? I'm slightly confused by this
> > report.
>
> Ah, it's the socket not the ops.
>
> > > KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027]
> > > CPU: 1 PID: 1083 Comm: syz-executor.3 Not tainted 5.16.0-rc2-syzkaller #0
> > > RIP: 0010:tls_build_proto net/tls/tls_main.c:776 [inline]
> > > [..]
> > >  __tcp_set_ulp net/ipv4/tcp_ulp.c:139 [inline]
> > >  tcp_set_ulp+0x428/0x4c0 net/ipv4/tcp_ulp.c:160
> > >  do_tcp_setsockopt+0x455/0x37c0 net/ipv4/tcp.c:3391
> > >  mptcp_setsockopt+0x1b47/0x2400 net/mptcp/sockopt.c:638
> > >
> > > Remove support for TCP_ULP setsockopt.
> > >
> > > Reported-by: syzbot+1fd9b69cde42967d1add@xxxxxxxxxxxxxxxxxxxxxxxxx
> > > Signed-off-by: Florian Westphal <fw@xxxxxxxxx>

Jakub -

If you could mark this as "Not Applicable" in netdevbpf patchwork, we'll 
apply it to the mptcp tree and resubmit to netdev with some related 
patches.

Thanks,

--
Mat Martineau
Intel