linux-kernel - Re: [PATCH v7 3/4] x86/dumpstack: Introduce die

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Date:   Tue, 31 Dec 2019 13:11:21 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Jann Horn <jannh@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH v7 3/4] x86/dumpstack: Introduce die_addr() for die()
 with #GP fault address

On Thu, Dec 19, 2019 at 12:11:49AM +0100, Jann Horn wrote:
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index c8b4ae6aed5b..4c691bb9e0d9 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -621,7 +621,10 @@ do_general_protection(struct pt_regs *regs, long error_code)
>  				 "maybe for address",
>  				 gp_addr);

 
> -		die(desc, regs, error_code);

I've added here:

                /*
                 * KASAN is interested only in the non-canonical case, clear it
                 * otherwise.
                 */

> +		if (hint != GP_NON_CANONICAL)
> +			gp_addr = 0;


otherwise you have:

	if (hint != GP_NO_HINT)
		...

	if (hint != GP_NON_CANONICAL)
		...

which is kinda confusing at a first glance and one has to follow the
code into die_addr() to figure out the usage of the address argument.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette