linux-kernel - Re: [PATCH] umh: fix UAF when the process is being killed

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Message-ID: <m2cz7j7zm2.fsf@gmail.com>
Date:   Fri, 13 Jan 2023 13:42:05 +0800
From:   Schspa Shi <schspa@...il.com>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com,
        linux-kernel@...r.kernel.org,
        syzbot+10d19d528d9755d9af22@...kaller.appspotmail.com,
        syzbot+70d5d5d83d03db2c813d@...kaller.appspotmail.com,
        syzbot+83cb0411d0fcf0a30fc1@...kaller.appspotmail.com
Subject: Re: [PATCH] umh: fix UAF when the process is being killed


Luis Chamberlain <mcgrof@...nel.org> writes:

> On Thu, Dec 22, 2022 at 08:09:38PM +0800, Schspa Shi wrote:
>> 
>> Attaching the full test program in case anyone wants to add some
>> comments.
>
> Good stuff.
>
> That looks like a kernel sefltest. So you can just add it as an
> initial selftest for completion so lib/test_completion.c and extend
> lib/Kconfig.debug for a new kconfig symbol for it, and then just add
> a script on tools/testing/selftets/completion/ with a simple makefile
> which references a script which just calls modprobe. You can look at
> tools/testing/selftests/kmod/ for an example.

OK, but I want to know, is it enough to add only positive examples for
the test items here? Do we need a reverse example to prove that the
previous writing is wrong?

>
> But I still think you may want an SmPL Coccinelle grammer patch to hunt
> down other users with this pattern. The beneefit is that then you can
> use the same Coccinelle patch to also then *fix* the issue in other
> places.
>

Yes, I'm learning about SmPL, and I'll add this syntax patch later to
find more problems.

> The current uaf on umh is not something I'm terribly concerned to be
> exploited in the wild. I don't think other use cases would be easier,
> but, all this work would close the gap completely.
>
> Thanks for doing this.
>
>   Luis


-- 
BRs
Schspa Shi