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@xxxxxxxxxxxx> 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@xxxxxxxxxx>
> 
> 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