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

From: Jonathan Cameron <jic23@kernel.org>
To: Sven Van Asbroeck <thesven73@gmail.com>
Cc: Hartmut Knaack <knaack.h@gmx.de>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
	Michal Simek <michal.simek@xilinx.com>,
	Manish Narani <manish.narani@xilinx.com>,
	linux-iio@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] iio: adc: xilinx: fix potential use-after-free on remove
Date: Sat, 16 Mar 2019 15:47:58 +0000	[thread overview]
Message-ID: <20190316154758.27c59b82@archlinux> (raw)
In-Reply-To: <20190310185826.25916-1-TheSven73@gmail.com>

On Sun, 10 Mar 2019 14:58:24 -0400
Sven Van Asbroeck <thesven73@gmail.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@gmail.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);
>  