The patch below does not apply to the 6.12-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-6.12.y git checkout FETCH_HEAD git cherry-pick -x 833d4313bc1e9e194814917d23e8874d6b651649 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025101604-chamber-playhouse-5278@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 833d4313bc1e9e194814917d23e8874d6b651649 Mon Sep 17 00:00:00 2001 From: "Matthieu Baerts (NGI0)" matttbe@kernel.org Date: Thu, 18 Sep 2025 10:50:18 +0200 Subject: [PATCH] mptcp: reset blackhole on success with non-loopback ifaces

When a first MPTCP connection gets successfully established after a blackhole period, 'active_disable_times' was supposed to be reset when this connection was done via any non-loopback interfaces.

Unfortunately, the opposite condition was checked: only reset when the connection was established via a loopback interface. Fixing this by simply looking at the opposite.

This is similar to what is done with TCP FastOpen, see tcp_fastopen_active_disable_ofo_check().

This patch is a follow-up of a previous discussion linked to commit 893c49a78d9f ("mptcp: Use __sk_dst_get() and dst_dev_rcu() in mptcp_active_enable()."), see [1].

Fixes: 27069e7cb3d1 ("mptcp: disable active MPTCP in case of blackhole") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/4209a283-8822-47bd-95b7-87e96d9b7ea3@kernel.org [1] Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org Reviewed-by: Simon Horman horms@kernel.org Reviewed-by: Kuniyuki Iwashima kuniyu@google.com Link: https://patch.msgid.link/20250918-net-next-mptcp-blackhole-reset-loopback-v1... Signed-off-by: Jakub Kicinski kuba@kernel.org

diff --git a/net/mptcp/ctrl.c b/net/mptcp/ctrl.c index e8ffa62ec183..d96130e49942 100644 --- a/net/mptcp/ctrl.c +++ b/net/mptcp/ctrl.c @@ -507,7 +507,7 @@ void mptcp_active_enable(struct sock *sk) rcu_read_lock(); dst = __sk_dst_get(sk); dev = dst ? dst_dev_rcu(dst) : NULL; - if (dev && (dev->flags & IFF_LOOPBACK)) + if (!(dev && (dev->flags & IFF_LOOPBACK))) atomic_set(&pernet->active_disable_times, 0); rcu_read_unlock(); }