Re: [PATCH 5/5] x86/traps: avoid KMSAN bugs originating from handle_bug()

Alexander Potapenko
2022-11-03T13:38:12Z

On Thu, Nov 3, 2022 at 12:18 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Wed, Nov 02, 2022 at 12:06:11PM +0100, Alexander Potapenko wrote:
>
> > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> > index 178015a820f08..d3fdec706f1d2 100644
> > --- a/arch/x86/kernel/traps.c
> > +++ b/arch/x86/kernel/traps.c
> > @@ -15,6 +15,7 @@
> > #include <linux/context_tracking.h>
> > #include <linux/interrupt.h>
> > #include <linux/kallsyms.h>
> > +#include <linux/kmsan.h>
> > #include <linux/spinlock.h>
> > #include <linux/kprobes.h>
> > #include <linux/uaccess.h>
> > @@ -301,6 +302,12 @@ static noinstr bool handle_bug(struct pt_regs *regs)
> > {
> > bool handled = false;
> >
> > + /*
> > + * Normally @regs are unpoisoned by irqentry_enter(), but handle_bug()
> > + * is a rare case that uses @regs without passing them to
> > + * irqentry_enter().
> > + */
> > + kmsan_unpoison_entry_regs(regs);
> > if (!is_valid_bugaddr(regs->ip))
> > return handled;
> >
>
> Should we place this kmsan_unpoison_entry_regs() after the
> instrumentation_begin() ?

Agreed, let me send an update.

--
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Liana Sebastian
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg