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mptcp: replace mptcp_disconnect with a stub 

Paolo points out that mptcp_disconnect is bogus:
"lock_sock(sk);
looks suspicious (lock should be already held by the caller)
And call to: tcp_disconnect(sk, flags); too, sk is not a tcp
socket".

->disconnect() gets called from e.g. inet_stream_connect when
one tries to disassociate a connected socket again (to re-connect
without closing the socket first).
MPTCP however uses mptcp_stream_connect, not inet_stream_connect,
for the mptcp-socket connect call.

inet_stream_connect only gets called indirectly, for the tcp socket,
so any ->disconnect() calls end up calling tcp_disconnect for that
tcp subflow sk.

This also explains why syzkaller has not yet reported a problem
here.  So for now replace this with a stub that doesn't do anything.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/14
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Westphal 2020-04-29 20:43:20 +02:00 committed by David S. Miller
parent 9812307491
commit 42c556fef9
1 changed files with 6 additions and 5 deletions
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11
net/mptcp/protocol.c
View File

@ -1316,11 +1316,12 @@ static void mptcp_copy_inaddrs(struct sock *msk, const struct sock *ssk)
static int mptcp_disconnect(struct sock *sk, int flags)
{
lock_sock(sk);
__mptcp_clear_xmit(sk);
release_sock(sk);
mptcp_cancel_work(sk);
return tcp_disconnect(sk, flags);
/* Should never be called.
* inet_stream_connect() calls ->disconnect, but that
* refers to the subflow socket, not the mptcp one.
*/
WARN_ON_ONCE(1);
return 0;
}
#if IS_ENABLED(CONFIG_MPTCP_IPV6)