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

Peter Zijlstra
2022-11-03T11:18:41Z

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() ?