Re: Crash in acpi_ns_validate_handle triggered by soundwire on Linux 5.10

Marcin Ślusarz
2021-02-01T12:17:46Z

pon., 1 lut 2021 o 12:43 Rafael J. Wysocki <rafael@kernel.org> napisał(a):
>
> On Fri, Jan 29, 2021 at 9:03 PM Marcin Ślusarz <marcin.slusarz@gmail.com> wrote:
> >
> > pt., 29 sty 2021 o 19:59 Marcin Ślusarz <marcin.slusarz@gmail.com> napisał(a):
> > >
> > > czw., 28 sty 2021 o 15:32 Marcin Ślusarz <marcin.slusarz@gmail.com> napisał(a):
> > > >
> > > > czw., 28 sty 2021 o 13:39 Rafael J. Wysocki <rafael@kernel.org> napisał(a):
> > > > > The only explanation for that I can think about (and which does not
> > > > > involve supernatural intervention so to speak) is a stack corruption
> > > > > occurring between these two calls in sdw_intel_acpi_cb(). IOW,
> > > > > something scribbles on the handle in the meantime, but ATM I have no
> > > > > idea what that can be.
> > > >
> > > > I tried KASAN but it didn't find anything and kernel actually booted
> > > > successfully.
> > >
> > > I investigated this and it looks like a compiler bug (or something nastier),
> > > but I can't find where exactly registers get corrupted because if I add printks
> > > the corruption seems on the printk side, but if I don't add them it seems
> > > the value gets corrupted earlier.
> > (...)
> > > I'm using gcc 10.2.1 from Debian testing.
> >
> > Someone on IRC, after hearing only that "gcc miscompiles the kernel",
> > suggested disabling CONFIG_STACKPROTECTOR_STRONG.
> > It helped indeed and it matches my observations, so it's quite likely it
> > is the culprit.
> >
> > What do we do now?
>
> Figure out why the stack protection kicks in, I suppose.
>
> The target object is not on the stack, so if the pointer to it is
> valid (we need to verify somehow that it is indeed), dereferencing it
> shouldn't cause the stack protection to trigger.

Well, the problem is not that stack protector finds something, but
the feature itself corrupts some registers.