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From:   Marco Elver <elver@google.com>
Date:   Mon, 24 Aug 2020 13:50:08 +0200
Message-ID: <CANpmjNNYhYwyzT3pBzJdb=XCGyLj7X+Fhqui-6JAZJWGys25Rg@mail.gmail.com>
Subject: Re: [PATCH v2 0/6] kasan: add workqueue and timer stack for generic KASAN
To:     Walter Wu <walter-zh.wu@mediatek.com>
Cc:     Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        John Stultz <john.stultz@linaro.org>,
        Stephen Boyd <sboyd@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Tejun Heo <tj@kernel.org>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        wsd_upstream <wsd_upstream@mediatek.com>,
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On Mon, 24 Aug 2020 at 10:07, Walter Wu <walter-zh.wu@mediatek.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@google.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