The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 0226436acf2495cde4b93e7400e5a87305c26054 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023072119-skipping-penalize-15f0@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

0226436acf24 ("mptcp: do not rely on implicit state check in mptcp_listen()") cfdcfeed6449 ("mptcp: introduce 'sk' to replace 'sock->sk' in mptcp_listen()")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0226436acf2495cde4b93e7400e5a87305c26054 Mon Sep 17 00:00:00 2001 From: Paolo Abeni pabeni@redhat.com Date: Tue, 4 Jul 2023 22:44:34 +0200 Subject: [PATCH] mptcp: do not rely on implicit state check in mptcp_listen()

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

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 489a3defdde5..3613489eb6e3 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -3703,6 +3703,11 @@ static int mptcp_listen(struct socket *sock, int backlog) pr_debug("msk=%p", msk);

lock_sock(sk); + + err = -EINVAL; + if (sock->state != SS_UNCONNECTED || sock->type != SOCK_STREAM) + goto unlock; + ssock = __mptcp_nmpc_socket(msk); if (IS_ERR(ssock)) { err = PTR_ERR(ssock);