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

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Date:   Sat, 11 Mar 2023 00:54:01 +0800
From:   Zheng Hacker <hackerzheng666@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Zheng Wang <zyytlz.wz@....com>, jdelvare@...e.com,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
        1395428693sheep@...il.com, alex000young@...il.com
Subject: Re: [PATCH] hwmon: (xgene) Fix use after free bug in
 xgene_hwmon_remove due to race condition

Guenter Roeck <linux@...ck-us.net> 于2023年3月11日周六 00:34写道：
>
> 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 for your effort.

Best regards,
Zheng
>
> > ---
> >  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)