FAILED: patch "[PATCH] mptcp: fix subflow bitfield misuse" failed to apply to 5.15-stable tree

[Sasha Levin <sashal@kernel.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 7538fa33bb2f66b8b809ff39d58308be48e197a0
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107060756-failed-5.15-7538fa33bb2f@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Thanks,
Sasha

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

From 7538fa33bb2f66b8b809ff39d58308be48e197a0 Mon Sep 17 00:00:00 2001
From: Paolo Abeni <pabeni@redhat.com>
Date: Tue, 13 Oct 2026 16:29:20 +0200
Subject: [PATCH] mptcp: fix subflow bitfield misuse

The subflow status bitfield is protected by the subflow socket lock,
with one notable exception: the `close_event_done` bit is actually under
the msk socket lock protection.

As reported by Clashiko [1], flipping the latter bit may corrupt other
entries in the same bitfield.

Move the `close_event_done` outside the bitfield, in a 32bit hole.

Link: https://lore.kernel.org/178959153492.22033.1944011998010756543@kernel.org
Fixes: d82809b6c5f2 ("mptcp: avoid duplicated SUB_CLOSED events")
Cc: stable@vger.kernel.org
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/20261013-net-mptcp-misc-fixes-7-3-rc8-v1-2-932c9b182fc7@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/mptcp/protocol.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 0384d6a023f9d..c006110b1c56d 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -583,14 +583,16 @@ struct mptcp_subflow_context {
 		closing : 1,	    /* must not pass rx data to msk anymore */
 		valid_csum_seen : 1,        /* at least one csum validated */
 		is_mptfo : 1,	    /* subflow is doing TFO */
-		close_event_done : 1,       /* has done the post-closed part */
 		mpc_drop : 1,	    /* the MPC option has been dropped in a rtx */
 		resetting : 1,	    /* subflow is resetting */
-		__unused : 8;
+		__unused : 9;
 	bool	data_avail;
 	bool	scheduled;
 	bool	pm_listener;	    /* a listener managed by the kernel PM? */
 	bool	fully_established;  /* path validated */
+	bool	close_event_done;   /* has done the post-closed part,
+				     * protected by msk socket lock
+				     */
 	u32	lent_mem_frag;
 	u32	remote_nonce;
 	u64	thmac;
-- 
2.53.0