linux-kernel - Re: [PATCH 5/5] x86/traps: avoid KMSAN bugs originating from handle

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Message-ID: <CAG_fn=XmODMP6rocAoCUGsOhDZmxr09PG_1WZewNg+-tcLhoWg@mail.gmail.com>
Date:   Thu, 3 Nov 2022 14:37:28 +0100
From:   Alexander Potapenko <glider@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org
Subject: Re: [PATCH 5/5] x86/traps: avoid KMSAN bugs originating from handle_bug()

On Thu, Nov 3, 2022 at 12:18 PM Peter Zijlstra <peterz@...radead.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

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