linux-kernel - Re: [PATCH] auxdisplay: ht16k33: fix potential user-after-free on module unload

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Message-ID: <CAGngYiXS0w1-z=o60aA-yfGPB1k6JejaUgU78g5eFDnxchZf9A@mail.gmail.com>
Date:   Sun, 10 Feb 2019 17:03:22 -0500
From:   Sven Van Asbroeck <thesven73@...il.com>
To:     Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc:     Robin van der Gracht <robin@...tonic.nl>,
        Tejun Heo <tj@...nel.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Sebastian Reichel <sre@...nel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] auxdisplay: ht16k33: fix potential user-after-free on
 module unload

On Fri, Feb 8, 2019 at 7:15 PM Miguel Ojeda
<miguel.ojeda.sandonis@...il.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@...il.com>
> Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>

Yes, this should do the trick.

Reviewed-by: Sven Van Asbroeck <TheSven73@...il.com>