Re: general protection fault in perf_misc_flags

[Dmitry Vyukov]

On Wed, Sep 30, 2020 at 6:31 PM Borislav Petkov <bp@xxxxxxxxx> wrote:
>
> On Wed, Sep 30, 2020 at 06:23:44PM +0200, Dmitry Vyukov wrote:
> > Here is the answer:
> > https://github.com/google/syzkaller/blob/master/tools/create-gce-image.sh#L189
> >
> > # rodata=n: mark_rodata_ro becomes very slow with KASAN (lots of PGDs)
> >
> > I have some vague memory that there was some debug double checking
> > that pages are indeed read-only and that debug check was slow, but it
> > was always executed without rodata=n.
>
> Sounds like debug_checkwx() which is disabled by turning off
> CONFIG_DEBUG_WX.
>
> You could either disable it in your .configs or, provided there's even
> such an option, disable KASAN checking around it until that one-time
> boot test completes and then reenable KASAN.

Thanks!

I've prepared a change that removes rodata=n:
https://github.com/google/syzkaller/pull/2155

I think we will be able to indirectly evaluate if it helps or not over
some period of time based on occurrence of any new similar crashes.