FAILED: patch "[PATCH] mptcp: pm: ADD_ADDR rtx: fix potential data-race" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

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 <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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 5cd6e0ad79d2615264f63929f8b457ad97ae550d
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026051216-stock-unloved-37a8@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From 5cd6e0ad79d2615264f63929f8b457ad97ae550d Mon Sep 17 00:00:00 2001
From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>
Date: Tue, 5 May 2026 17:00:51 +0200
Subject: [PATCH] mptcp: pm: ADD_ADDR rtx: fix potential data-race

This mptcp_pm_add_timer() helper is executed as a timer callback in
softirq context. To avoid any data races, the socket lock needs to be
held with bh_lock_sock().

If the socket is in use, retry again soon after, similar to what is done
with the keepalive timer.

Fixes: 00cfd77b9063 ("mptcp: retransmit ADD_ADDR when timeout")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260505-net-mptcp-pm-fixes-7-1-rc3-v1-3-fca8091060a4@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index 5056eb8db24e..3912128d9b86 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -337,6 +337,13 @@ static void mptcp_pm_add_timer(struct timer_list *timer)
 	if (inet_sk_state_load(sk) == TCP_CLOSE)
 		return;
 
+	bh_lock_sock(sk);
+	if (sock_owned_by_user(sk)) {
+		/* Try again later. */
+		sk_reset_timer(sk, timer, jiffies + HZ / 20);
+		goto out;
+	}
+
 	if (mptcp_pm_should_add_signal_addr(msk)) {
 		sk_reset_timer(sk, timer, jiffies + TCP_RTO_MAX / 8);
 		goto out;
@@ -365,6 +372,7 @@ static void mptcp_pm_add_timer(struct timer_list *timer)
 		mptcp_pm_subflow_established(msk);
 
 out:
+	bh_unlock_sock(sk);
 	__sock_put(sk);
 }