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SubjectRe: [PATCH] auxdisplay: ht16k33: fix potential user-after-free on module unload
On Sat, 9 Feb 2019 01:15:22 +0100
Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> wrote:

> On module unload/remove, we need to ensure that work does not run
> after we have freed resources. Concretely, cancel_delayed_work()
> may return while the callback function is still running.
>
> From kernel/workqueue.c:
>
> The work callback function may still be running on return,
> unless it returns true and the work doesn't re-arm itself.
> Explicitly flush or use cancel_delayed_work_sync() to wait on it.
>
> Link: https://lore.kernel.org/lkml/20190204220952.30761-1-TheSven73@googlemail.com/
> Reported-by: Sven Van Asbroeck <thesven73@gmail.com>
> Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
> ---
> drivers/auxdisplay/ht16k33.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/auxdisplay/ht16k33.c b/drivers/auxdisplay/ht16k33.c
> index a43276c76fc6..21393ec3b9a4 100644
> --- a/drivers/auxdisplay/ht16k33.c
> +++ b/drivers/auxdisplay/ht16k33.c
> @@ -509,7 +509,7 @@ static int ht16k33_remove(struct i2c_client *client)
> struct ht16k33_priv *priv = i2c_get_clientdata(client);
> struct ht16k33_fbdev *fbdev = &priv->fbdev;
>
> - cancel_delayed_work(&fbdev->work);
> + cancel_delayed_work_sync(&fbdev->work);
> unregister_framebuffer(fbdev->info);
> framebuffer_release(fbdev->info);
> free_page((unsigned long) fbdev->buffer);

Looks good

Acked-by: Robin van der Gracht <robin@protonic.nl>

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