Subject: FAILED: patch "[PATCH] wifi: mac80211: shut down RX BA session timer on teardown" failed to apply to 5.15-stable tree
To: enderaoelyther@gmail.com,johannes.berg@intel.com
Cc: <stable@vger.kernel.org>
From: <gregkh@linuxfoundation.org>
Date: Mon, 05 Oct 2026 16:38:05 +0200
Message-ID: <2026100505-decompose-decaf-fb38@gregkh>
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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 e588e83e5c7a0f6d7a77dbbb58927c8c8cfd598e
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026100505-decompose-decaf-fb38@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:


thanks,

greg k-h

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

From e588e83e5c7a0f6d7a77dbbb58927c8c8cfd598e Mon Sep 17 00:00:00 2001
From: Zhao Li <enderaoelyther@gmail.com>
Date: Thu, 10 Sep 2026 14:54:02 +0800
Subject: [PATCH] wifi: mac80211: shut down RX BA session timer on teardown

Tearing down an RX BA session can leave the session timer queued on a
freed tid_rx. Later timer-wheel processing and the timer callback itself
then run against freed memory.

An RX BAR handler can dereference tid_rx under RCU before teardown
unpublishes it and stay in its read-side critical section while teardown
deletes the session timer. The stale handler can then rearm the timer
after timer_delete_sync() returns and before the RCU callback frees
tid_rx.

Use timer_shutdown_sync() so rearm attempts become ineffective once
teardown starts. Keep reorder_timer unchanged: teardown marks the session
removed under reorder_lock and its release path checks that state before
rearming. session_timer has no equivalent guard because
ieee80211_rx_h_ctrl() rearms it before taking reorder_lock.

Fixes: a87f736d942c ("mac80211: use RCU for RX aggregation")
Cc: stable@kernel.org # 5.15+
Assisted-by: LLM sparse kasan
Signed-off-by: Zhao Li <enderaoelyther@gmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/agg-rx.c b/net/mac80211/agg-rx.c
index 9629e00069a1..01d6703767c6 100644
--- a/net/mac80211/agg-rx.c
+++ b/net/mac80211/agg-rx.c
@@ -102,7 +102,7 @@ void __ieee80211_stop_rx_ba_session(struct sta_info *sta, u16 tid,
 	if (!tid_rx)
 		return;
 
-	timer_delete_sync(&tid_rx->session_timer);
+	timer_shutdown_sync(&tid_rx->session_timer);
 
 	/* make sure ieee80211_sta_reorder_release() doesn't re-arm the timer */
 	spin_lock_bh(&tid_rx->reorder_lock);