linux-kernel - Re: [PATCH] Bluetooth: hci_qca: Use del_timer

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Date:   Mon, 4 Apr 2022 17:22:00 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        Ben Young Tae Kim <ytkim@....qualcomm.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] Bluetooth: hci_qca: Use del_timer_sync() before freeing


On 4/4/22 15:22, Steven Rostedt wrote:
> [ Resending due to cut and paste failure of email address ]
>
> From: Steven Rostedt (Google) <rostedt@...dmis.org>
>
> 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.
>
> Cc: stable@...r.kernel.org
> Fixes: 0ff252c1976da ("Bluetooth: hciuart: Add support QCA chipset for
> UART") Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> ---
> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> index f6e91fb432a3..73a8c72b5aae 100644
> --- a/drivers/bluetooth/hci_qca.c
> +++ b/drivers/bluetooth/hci_qca.c
> @@ -696,8 +696,8 @@ 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);
> +	del_timer_sync(&qca->tx_idle_timer);
> +	del_timer_sync(&qca->wake_retrans_timer);


It seems the wake_retrans_timer could be re-armed from a work queue.

So perhaps we need to make sure qca->workqueue is destroyed

before these del_timer_sync() calls ?

>   	destroy_workqueue(qca->workqueue);


ie move this destroy_workqueue() up ?


>   	qca->hu = NULL;
>