linux-kernel - Re: [PATCH] hwmon: (xgene) Fix use after free bug in xgene_hwmon

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Date:   Fri, 10 Mar 2023 08:34:03 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Zheng Wang <zyytlz.wz@....com>
Cc:     jdelvare@...e.com, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org, hackerzheng666@...il.com,
        1395428693sheep@...il.com, alex000young@...il.com
Subject: Re: [PATCH] hwmon: (xgene) Fix use after free bug in
 xgene_hwmon_remove due to race condition

On Fri, Mar 10, 2023 at 04:40:07PM +0800, Zheng Wang wrote:
> In xgene_hwmon_probe, &ctx->workq is bound with
> xgene_hwmon_evt_work. Then it will be started.
> 
> If we remove the driver which will call
> xgene_hwmon_remove to make cleanup, there may
> be a unfinished work.
> 
> The possiblesequence is as follows:
> 
> Fix it by finishing the work before cleanup in the
> xgene_hwmon_remove
> 
> CPU0                  CPU1
> 
>                     |xgene_hwmon_evt_work
> xgene_hwmon_remove   |
> kfifo_free(&ctx->async_msg_fifo);|
>                     |
>                     |kfifo_out_spinlocked
>                     |//use &ctx->async_msg_fifo
> Fixes: 2ca492e22cb7 ("hwmon: (xgene) Fix crash when alarm occurs before driver probe")
> Signed-off-by: Zheng Wang <zyytlz.wz@....com>

Applied.

Thanks,
Guenter

> ---
>  drivers/hwmon/xgene-hwmon.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/hwmon/xgene-hwmon.c b/drivers/hwmon/xgene-hwmon.c
> index 5cde837bfd09..d1abea49f01b 100644
> --- a/drivers/hwmon/xgene-hwmon.c
> +++ b/drivers/hwmon/xgene-hwmon.c
> @@ -761,6 +761,7 @@ static int xgene_hwmon_remove(struct platform_device *pdev)
>  {
>  	struct xgene_hwmon_dev *ctx = platform_get_drvdata(pdev);
>  
> +	cancel_work_sync(&ctx->workq);
>  	hwmon_device_unregister(ctx->hwmon_dev);
>  	kfifo_free(&ctx->async_msg_fifo);
>  	if (acpi_disabled)