RE: [PATCH v2] kasan: fix deadlock in start_report()

[袁帅(Shuai Yuan)]

On Friday, February 10, 2023 at 6:54 AM Andrey Konovalov <andreyknvl@xxxxxxxxx>
wrote:
> On Thu, Feb 9, 2023 at 11:44 AM Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> wrote:
> >
> >  On Thu, 9 Feb 2023 at 10:19, 袁帅(Shuai Yuan) <yuanshuai@xxxxxxxx>
> wrote:
> > >
> > > Hi Dmitry Vyukov
> > >
> > > Thanks, I see that your means.
> > >
> > > Currently, report_suppressed() seem not work in Kasan-HW mode, it
> always return false.
> > > Do you think should change the report_suppressed function?
> > > I don't know why CONFIG_KASAN_HW_TAGS was blocked separately
> before.
> >
> > That logic was added by Andrey in:
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/com
> > mit/?id=c068664c97c7cf
> >
> > Andrey, can we make report_enabled() check current->kasan_depth and
> > remove report_suppressed()?
>
> I decided to not use kasan_depth for HW_TAGS, as we can always use a
> match-all tag to make "invalid" memory accesses.
>
> I think we can fix the reporting code to do exactly that so that it doesn't
> cause MTE faults.
>
> Shuai, could you clarify, at which point due kasan_report_invalid_free an
> MTE exception is raised in your tests?

Yes, I need some time to clarify this problem with a clear log by test.

> > Then we can also remove the comment in kasan_report_invalid_free().
> >
> > It looks like kasan_disable_current() in kmemleak needs to affect
> > HW_TAGS mode as well:
> > https://elixir.bootlin.com/linux/v6.2-rc7/source/mm/kmemleak.c#L301
>
> It uses kasan_reset_tag, so it should work properly with HW_TAGS.
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