linux-kernel - Re: [PATCH v2 0/6] kasan: add workqueue and timer stack for generic KASAN

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Date:   Mon, 24 Aug 2020 13:50:08 +0200
From:   Marco Elver <elver@...gle.com>
To:     Walter Wu <walter-zh.wu@...iatek.com>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        John Stultz <john.stultz@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        wsd_upstream <wsd_upstream@...iatek.com>,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v2 0/6] kasan: add workqueue and timer stack for generic KASAN

On Mon, 24 Aug 2020 at 10:07, Walter Wu <walter-zh.wu@...iatek.com> wrote:
>
> Syzbot reports many UAF issues for workqueue or timer, see [1] and [2].
> In some of these access/allocation happened in process_one_work(),
> we see the free stack is useless in KASAN report, it doesn't help
> programmers to solve UAF on workqueue. The same may stand for times.
>
> This patchset improves KASAN reports by making them to have workqueue
> queueing stack and timer queueing stack information. It is useful for
> programmers to solve use-after-free or double-free memory issue.
>
> Generic KASAN will record the last two workqueue and timer stacks,
> print them in KASAN report. It is only suitable for generic KASAN.
>
> [1]https://groups.google.com/g/syzkaller-bugs/search?q=%22use-after-free%22+process_one_work
> [2]https://groups.google.com/g/syzkaller-bugs/search?q=%22use-after-free%22%20expire_timers
> [3]https://bugzilla.kernel.org/show_bug.cgi?id=198437
>
> Walter Wu (6):
> timer: kasan: record timer stack
> workqueue: kasan: record workqueue stack
> kasan: print timer and workqueue stack
> lib/test_kasan.c: add timer test case
> lib/test_kasan.c: add workqueue test case
> kasan: update documentation for generic kasan
>
> ---
>
> Changes since v1:
> - Thanks for Marco and Thomas suggestion.
> - Remove unnecessary code and fix commit log
> - reuse kasan_record_aux_stack() and aux_stack
>   to record timer and workqueue stack.
> - change the aux stack title for common name.

Much cleaner.

In general,

Acked-by: Marco Elver <elver@...gle.com>

but I left some more comments. I'm a bit worried about the tests,
because of KASAN-test KUnit rework, but probably not much we can do
until these are added to -mm tree.

Thanks,
-- Marco