linux-kernel - Re: [PATCH mptcp] mptcp: remove tcp ulp setsockopt support

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Date:   Mon, 6 Dec 2021 10:44:16 -0800 (PST)
From:   Mat Martineau <mathew.j.martineau@...ux.intel.com>
To:     Jakub Kicinski <kuba@...nel.org>
cc:     Florian Westphal <fw@...len.de>, mptcp@...ts.linux.dev,
        syzkaller-bugs@...glegroups.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        syzbot+1fd9b69cde42967d1add@...kaller.appspotmail.com
Subject: Re: [PATCH mptcp] mptcp: remove tcp ulp setsockopt support

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@...kaller.appspotmail.com
>>> Signed-off-by: Florian Westphal <fw@...len.de>

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