On Mon, 2020-08-10 at 19:50 +0800, Walter Wu wrote:
> On Mon, 2020-08-10 at 07:19 -0400, Qian Cai wrote:
> >
> > > On Aug 10, 2020, at 3:21 AM, Walter Wu <
walter...@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.
> > >
> > > In order to print the last two workqueue and timer stacks, so that
> > > we add new members in struct kasan_alloc_meta.
> > > - two workqueue queueing work stacks, total size is 8 bytes.
> > > - two timer queueing stacks, total size is 8 bytes.
> > >
> > > Orignial struct kasan_alloc_meta size is 16 bytes. After add new
> > > members, then the struct kasan_alloc_meta total size is 32 bytes,
> > > It is a good number of alignment. Let it get better memory consumption.
> >
> > Getting debugging tools complicated surely is the best way to kill it. I would argue that it only make sense to complicate it if it is useful most of the time which I never feel or hear that is the case. This reminds me your recent call_rcu() stacks that most of time just makes parsing the report cumbersome. Thus, I urge this exercise to over-engineer on special cases need to stop entirely.
> >
>
> A good debug tool is to have complete information in order to solve
> issue. We should focus on if KASAN reports always show this debug
> information or create a option to decide if show it. Because this
> feature is Dmitry's suggestion. see [1]. So I think it need to be
Fix name typo. I am sorry to him.
And add a bugzilla to show why need to do it. please see [1].