FAILED: patch "[PATCH] Bluetooth: hci_qca: Use del_timer_sync() before freeing" failed to apply to 4.9-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.9-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>.

thanks,

greg k-h

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

From 72ef98445aca568a81c2da050532500a8345ad3a Mon Sep 17 00:00:00 2001
From: Steven Rostedt <rostedt@goodmis.org>
Date: Tue, 5 Apr 2022 10:02:00 -0400
Subject: [PATCH] Bluetooth: hci_qca: Use del_timer_sync() before freeing

While looking at a crash report on a timer list being corrupted, which
usually happens when a timer is freed while still active. This is
commonly triggered by code calling del_timer() instead of
del_timer_sync() just before freeing.

One possible culprit is the hci_qca driver, which does exactly that.

Eric mentioned that wake_retrans_timer could be rearmed via the work
queue, so also move the destruction of the work queue before
del_timer_sync().

Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: stable@vger.kernel.org
Fixes: 0ff252c1976da ("Bluetooth: hciuart: Add support QCA chipset for UART")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
index f6e91fb432a3..eab34e24d944 100644
--- a/drivers/bluetooth/hci_qca.c
+++ b/drivers/bluetooth/hci_qca.c
@@ -696,9 +696,9 @@ static int qca_close(struct hci_uart *hu)
 	skb_queue_purge(&qca->tx_wait_q);
 	skb_queue_purge(&qca->txq);
 	skb_queue_purge(&qca->rx_memdump_q);
-	del_timer(&qca->tx_idle_timer);
-	del_timer(&qca->wake_retrans_timer);
 	destroy_workqueue(qca->workqueue);
+	del_timer_sync(&qca->tx_idle_timer);
+	del_timer_sync(&qca->wake_retrans_timer);
 	qca->hu = NULL;
 
 	kfree_skb(qca->rx_skb);