linux-kernel - Re: [RFC v1 0/3] Address potential user-after-free on module unload

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Message-ID: <CANiq72=1f7NtehzbzL0G-qHSvORAfeyYXYHjzfBkBQX46VBxsQ@mail.gmail.com>
Date:   Thu, 14 Feb 2019 02:11:09 +0100
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     Sven Van Asbroeck <thesven73@...il.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Kees Cook <keescook@...omium.org>, Tejun Heo <tj@...nel.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Sebastian Reichel <sre@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [RFC v1 0/3] Address potential user-after-free on module unload

Hi Sven,

On Sun, Feb 10, 2019 at 7:05 PM Sven Van Asbroeck <thesven73@...il.com> wrote:
>
> For relatively straightforward problems, I'd say yes.
>
> However, the problems flagged by this script are not trivial at all.
> In many cases, the missing _sync is just a symptom of general
> synchronization issues on disconnect(), and simply adding it
> will not fix the problem. Sometimes, it's just a false positive.

Indeed! Note that I didn't mean to say they are trivial issues or that
the solution is simply to replace cancel_delayed_work() with the
_sync() version in all cases -- only that it might be a good idea to
suggest its existence (instead of only suggesting devm_, because in
cases like drivers/auxdisplay/ht16k33.c it may be the simplest fix).

Cheers,
Miguel