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

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Message-ID: <CAGngYiUwaWPp7=TTAN3tqPz+D+1GsPDM7uFNYY1XSTYMMm+=aA@mail.gmail.com>
Date:   Sun, 10 Feb 2019 13:05:04 -0500
From:   Sven Van Asbroeck <thesven73@...il.com>
To:     Miguel Ojeda <miguel.ojeda.sandonis@...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 Miguel,

On Thu, Feb 7, 2019 at 11:30 PM Miguel Ojeda
<miguel.ojeda.sandonis@...il.com> wrote:
>
> Similarly, in drivers/auxdisplay/ht16k33.c, the cancel_delayed_work()
> is there, instead of cancel_delayed_work_sync(). Having the script
> suggest this change would be useful, too (i.e. instead of the devm_
> change, assuming the cancel_delayed_work() is already there).
>

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.