linux-kernel - Re: [PATCH v3 0/6] kasan: add workqueue and timer stack for generic KASAN

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Date:   Sun, 13 Sep 2020 12:17:33 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Marco Elver <elver@...gle.com>,
        Walter Wu <walter-zh.wu@...iatek.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...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 v3 0/6] kasan: add workqueue and timer stack for generic KASAN

On Wed, Aug 26, 2020 at 2:30 PM 'Andrey Konovalov' via kasan-dev
<kasan-dev@...glegroups.com> wrote:
>
> On Tue, Aug 25, 2020 at 10:26 AM 'Marco Elver' via kasan-dev
> <kasan-dev@...glegroups.com> wrote:
> >
> > On Tue, 25 Aug 2020 at 03:57, 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 stack information. It is useful for programmers
> > > to solve use-after-free or double-free memory issue.
> > >
> > > Generic KASAN also records the last two workqueue and timer stacks and
> > > prints 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
> >
> > Acked-by: Marco Elver <elver@...gle.com>
>
> Reviewed-by: Andrey Konovalov <andreyknvl@...gle.com>

Reviewed-by: Dmitry Vyukov <dvyukov@...gle.com>

Thanks! The UAF reports with RCU stacks that I see now are just 🔥🔥🔥

> > > ---
> > >
> > > Changes since v2:
> > > - modify kasan document to be more readable.
> > >   Thanks for Marco suggestion.
> > >
> > > 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.
> > >
> > > ---
> > >
> > > Documentation/dev-tools/kasan.rst |  4 ++--
> > > kernel/time/timer.c               |  3 +++
> > > kernel/workqueue.c                |  3 +++
> > > lib/test_kasan.c                  | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > > mm/kasan/report.c                 |  4 ++--
> > > 5 files changed, 64 insertions(+), 4 deletions(-)
> > >
> > > --
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> >
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