Hi Greg, Sasha,
On 27/07/2023 16:16, Matthieu Baerts wrote:
From: Paolo Abeni pabeni@redhat.com
commit 0226436acf2495cde4b93e7400e5a87305c26054 upstream.
Since the blamed commit, closing the first subflow resets the first subflow socket state to SS_UNCONNECTED.
The current mptcp listen implementation relies only on such state to prevent touching not-fully-disconnected sockets.
Incoming mptcp fastclose (or paired endpoint removal) unconditionally closes the first subflow.
All the above allows an incoming fastclose followed by a listen() call to successfully race with a blocking recvmsg(), potentially causing the latter to hit a divide by zero bug in cleanup_rbuf/__tcp_select_window().
Address the issue explicitly checking the msk socket state in mptcp_listen(). An alternative solution would be moving the first subflow socket state update into mptcp_disconnect(), but in the long term the first subflow socket should be removed: better avoid relaying on it for internal consistency check.
Fixes: b29fcfb54cd7 ("mptcp: full disconnect implementation") Cc: stable@vger.kernel.org Reported-by: Christoph Paasch cpaasch@apple.com Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/414 Signed-off-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Matthieu Baerts matthieu.baerts@tessares.net Signed-off-by: Matthieu Baerts matthieu.baerts@tessares.net Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Matthieu Baerts matthieu.baerts@tessares.net
Backport notes:
- Conflicting with a cleanup that has been done after v6.1, see commit cfdcfeed6449 ("mptcp: introduce 'sk' to replace 'sock->sk' in mptcp_listen()").
Sasha just backported this commit cfdcfeed6449 ("mptcp: introduce 'sk' to replace 'sock->sk' in mptcp_listen()") so 0226436acf24 ("mptcp: do not rely on implicit state check in mptcp_listen()") can be applied without conflict. Thank you for that, good idea, it works for me!
Please drop this patch here then.
Cheers, Matt