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

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

[Walter Wu]

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.

---

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(-)

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

[Marco Elver]

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

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

[Walter Wu]

On Mon, 2020-08-24 at 13:50 +0200, Marco Elver wrote:
> 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.
> 

Hi Marco,

Thanks for your review and friendly reminder.

If needed, I will rebase and resend the test case.


Walter

> Thanks,
> -- Marco