netdev - [PATCH net 1/4] mptcp: remove tcp ulp setsockopt support

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Message-Id: <20211214231604.211016-2-mathew.j.martineau@linux.intel.com>
Date:   Tue, 14 Dec 2021 15:16:01 -0800
From:   Mat Martineau <mathew.j.martineau@...ux.intel.com>
To:     netdev@...r.kernel.org
Cc:     Florian Westphal <fw@...len.de>, davem@...emloft.net,
        kuba@...nel.org, matthieu.baerts@...sares.net,
        mptcp@...ts.linux.dev, pabeni@...hat.com,
        syzbot+1fd9b69cde42967d1add@...kaller.appspotmail.com,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>
Subject: [PATCH net 1/4] mptcp: remove tcp ulp setsockopt support

From: Florian Westphal <fw@...len.de>

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:

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.

Fixes: d9e4c1291810 ("mptcp: only admit explicitly supported sockopt")
Reported-by: syzbot+1fd9b69cde42967d1add@...kaller.appspotmail.com
Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
---
 net/mptcp/sockopt.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index 0f1e661c2032..f8efd478ac97 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -525,7 +525,6 @@ static bool mptcp_supported_sockopt(int level, int optname)
 		case TCP_NODELAY:
 		case TCP_THIN_LINEAR_TIMEOUTS:
 		case TCP_CONGESTION:
-		case TCP_ULP:
 		case TCP_CORK:
 		case TCP_KEEPIDLE:
 		case TCP_KEEPINTVL:
-- 
2.34.1