This is a note to let you know that I've just added the patch titled

    mptcp: close race between scheduler and state change

to the 6.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mptcp-close-race-between-scheduler-and-state-change.patch
and it can be found in the queue-6.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From stable+bounces-338601-greg=kroah.com@vger.kernel.org Sat Sep 19 21:57:24 2026
From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>
Date: Sat, 19 Sep 2026 21:56:47 +0200
Subject: mptcp: close race between scheduler and state change
To: mptcp@lists.linux.dev, stable@vger.kernel.org, gregkh@linuxfoundation.org
Cc: Paolo Abeni <pabeni@redhat.com>, sashal@kernel.org, Shardul Bankar <shardul.b@mpiricsoftware.com>, Xinyang Ge <xinyang@anthropic.com>, "Matthieu Baerts (NGI0)" <matttbe@kernel.org>, Jakub Kicinski <kuba@kernel.org>
Message-ID: <20260919195642.1977885-11-matttbe@kernel.org>

From: Paolo Abeni <pabeni@redhat.com>

commit 42064de57fb83231fcc89663a94885f228a1ee53 upstream.

The mptcp scheduler may race with subflow sockets state change: data
transmission on the selected socket may fail and a later release could
try to use mss_now reset to 0 for a divide operation.

Address the issue by explicitly checking for the critical scenario.

Fixes: c886d70286bf ("mptcp: do not queue data on closed subflows")
Cc: stable@vger.kernel.org
Reported-by: Shardul Bankar <shardul.b@mpiricsoftware.com>
Reported-by: Xinyang Ge <xinyang@anthropic.com>
Closes: https://lore.kernel.org/20260525194828.1137119-1-shardul.b@mpiricsoftware.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260917-net-mptcp-misc-fixes-7-3-rc4-v2-2-0cf5c72667c8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/mptcp/protocol.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1567,7 +1567,9 @@ struct sock *mptcp_subflow_get_send(stru
 
 static void mptcp_push_release(struct sock *ssk, struct mptcp_sendmsg_info *info)
 {
-	tcp_push(ssk, 0, info->mss_now, tcp_sk(ssk)->nonagle, info->size_goal);
+	if (info->mss_now)
+		tcp_push(ssk, 0, info->mss_now, tcp_sk(ssk)->nonagle,
+			 info->size_goal);
 	release_sock(ssk);
 }
 


Patches currently in stable-queue which might be from matttbe@kernel.org are

queue-6.12/mptcp-annotate-data-races-around-subflow-fully_established.patch
queue-6.12/selftests-mptcp-fix-an-uaf-in-mptcp_connect.c.patch
queue-6.12/mptcp-fix-bad-accounting-in-__mptcp_subflow_push_pending.patch
queue-6.12/mptcp-syncookies-remember-the-request-backup-flag.patch
queue-6.12/mptcp-remove-unneeded-read_once-annotation.patch
queue-6.12/mptcp-close-race-between-scheduler-and-state-change.patch
queue-6.12/tcp-use-gfp_atomic-in-tcp_send_active_reset.patch
queue-6.12/mptcp-avoid-unneeded-actions-on-subflow-reset.patch
queue-6.12/mptcp-options-handle-mpc-data-csum-reqd-no-csum.patch
queue-6.12/mptcp-subflow-no-need-to-copy-thmac-during-ulp_clone.patch