On 1/13/21 11:21 AM, Eric Dumazet wrote:
>
>
> On 1/12/21 6:25 PM, Paolo Abeni wrote:
>> Instead of re-implementing most of inet_shutdown, re-use
>> such helper, and implement the MPTCP-specific bits at the
>> 'proto' level.
>>
>> The msk-level disconnect() can now be invoked, lets provide a
>> suitable implementation.
>>
>> As a side effect, this fixes bad state management for listener
>> sockets. The latter could lead to division by 0 oops since
>> commit ea4ca586b16f ("mptcp: refine MPTCP-level ack scheduling").
>>
>> Fixes: 43b54c6ee382 ("mptcp: Use full MPTCP-level disconnect state machine")
>> Fixes: ea4ca586b16f ("mptcp: refine MPTCP-level ack scheduling")
>> Signed-off-by: Paolo Abeni <pab...@redhat.com>
>> ---
>> net/mptcp/protocol.c | 62 ++++++++++++--------------------------------
>> 1 file changed, 17 insertions(+), 45 deletions(-)
>>
>> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
>> index 2ff8c7caf74f..81faeff8f3bb 100644
>> --- a/net/mptcp/protocol.c
>> +++ b/net/mptcp/protocol.c
>> @@ -2642,11 +2642,12 @@ static void mptcp_copy_inaddrs(struct sock *msk,
>> const struct sock *ssk)
>>
>> static int mptcp_disconnect(struct sock *sk, int 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);
>> + struct mptcp_subflow_context *subflow;
>> + struct mptcp_sock *msk = mptcp_sk(sk);
>> +
>> + __mptcp_flush_join_list(msk);
>> + mptcp_for_each_subflow(msk, subflow)
>> + tcp_disconnect(mptcp_subflow_tcp_sock(subflow), flags);
>
> Ouch.
>
> tcp_disconnect() is supposed to be called with socket lock being held.
>
> Really, CONFIG_LOCKDEP=y should have warned you :/
Or maybe CONFIG_PROVE_RCU=y is needed to catch the bug.
