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

[Peter Zijlstra]

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() ?