linux-kernel - Re: [PATCH 1/3] iio: adc: xilinx: fix potential use-after-free on remove

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Message-ID: <20190316154758.27c59b82@archlinux>
Date:   Sat, 16 Mar 2019 15:47:58 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Sven Van Asbroeck <thesven73@...il.com>
Cc:     Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Michal Simek <michal.simek@...inx.com>,
        Manish Narani <manish.narani@...inx.com>,
        linux-iio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] iio: adc: xilinx: fix potential use-after-free on
 remove

On Sun, 10 Mar 2019 14:58:24 -0400
Sven Van Asbroeck <thesven73@...il.com> wrote:

> When cancel_delayed_work() returns, the delayed work may still
> be running. This means that the core could potentially free
> the private structure (struct xadc) while the delayed work
> is still using it. This is a potential use-after-free.
> 
> Fix by calling cancel_delayed_work_sync(), which waits for
> any residual work to finish before returning.
> 
> Signed-off-by: Sven Van Asbroeck <TheSven73@...il.com>
This appears 'obviously correct' to me so I'll apply it to the fixes
togreg branch of iio.git and mark it for stable.

However I won't be sending a pull request for that branch until at
least next weekend, so if anyone more familiar with the hardware
has a chance to take a look that would be great.

Applied to the fixes-togreg branch of iio.git.

Thanks,

Jonathan

> ---
>  drivers/iio/adc/xilinx-xadc-core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/adc/xilinx-xadc-core.c b/drivers/iio/adc/xilinx-xadc-core.c
> index 3f6be5ac049a..1960694e8007 100644
> --- a/drivers/iio/adc/xilinx-xadc-core.c
> +++ b/drivers/iio/adc/xilinx-xadc-core.c
> @@ -1320,7 +1320,7 @@ static int xadc_remove(struct platform_device *pdev)
>  	}
>  	free_irq(xadc->irq, indio_dev);
>  	clk_disable_unprepare(xadc->clk);
> -	cancel_delayed_work(&xadc->zynq_unmask_work);
> +	cancel_delayed_work_sync(&xadc->zynq_unmask_work);
>  	kfree(xadc->data);
>  	kfree(indio_dev->channels);
>