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

[Marco Elver <elver@google.com>]

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