FAILED: patch "[PATCH] sctp: close UDP tunnel sockets during netns teardown" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-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 <[email protected]>.

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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x ffb2bd7ade36ec4da32c46a6eddbf4515316d08c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026072946-semantic-plenty-6e1e@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From ffb2bd7ade36ec4da32c46a6eddbf4515316d08c Mon Sep 17 00:00:00 2001
From: Zhiling Zou <[email protected]>
Date: Wed, 15 Jul 2026 09:50:11 +0800
Subject: [PATCH] sctp: close UDP tunnel sockets during netns teardown

proc_sctp_do_udp_port() starts per-net SCTP UDP tunneling sockets when net.sctp.udp_port is set, and stops/restarts them when the sysctl value changes. The netns exit path does not stop these sockets, so a namespace can be torn down while its SCTP UDP tunnel sockets are still installed.

Close the UDP tunnel sockets from sctp_ctrlsock_exit() after unregistering the per-net sysctl table. This prevents new sysctl writes from racing in while the sockets are being released, and closes the sockets before the control socket is destroyed.

index 49d9740b1e0f..27c26e12f95d 100644
@@ -1460,6 +1460,7 @@ static int __net_init sctp_ctrlsock_init(struct net *net)
 static void __net_exit sctp_ctrlsock_exit(struct net *net)
 {
 	sctp_sysctl_net_unregister(net);
+	sctp_udp_sock_stop(net);
 
 	/* Free the control endpoint.  */
 	inet_ctl_sock_destroy(net->sctp.ctl_sock);