linux-kernel - Re: [PATCH v4 04/36] x86/bugs: Restructure rfds mitigation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <h7p644ejmyef2x6jau7wonbqufrtknyifza5ey2fjmz3bqfvas@xh5olvfqktg5>
Date: Thu, 10 Apr 2025 09:24:38 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: David Kaplan <david.kaplan@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, 
	Peter Zijlstra <peterz@...radead.org>, Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, 
	Ingo Molnar <mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org, 
	Brendan Jackman <jackmanb@...gle.com>, Derek Manwaring <derekmn@...zon.com>
Subject: Re: [PATCH v4 04/36] x86/bugs: Restructure rfds mitigation

On Mon, Mar 10, 2025 at 11:39:51AM -0500, David Kaplan wrote:
>  static void __init rfds_select_mitigation(void)
>  {
>  	if (!boot_cpu_has_bug(X86_BUG_RFDS) || cpu_mitigations_off()) {
>  		rfds_mitigation = RFDS_MITIGATION_OFF;
>  		return;
>  	}
> -	if (rfds_mitigation == RFDS_MITIGATION_OFF)
> -		return;

The removal of this RFDS_MITIGATION_OFF check can cause
verw_mitigation_selected to get wrongly enabled below if it was
RFDS_MITIGATION_OFF to begin with.

I think it's only a bisection issue, that gets re-added later with
"x86/bugs: Add attack vector controls for rfds".

>  
>  	if (rfds_mitigation == RFDS_MITIGATION_AUTO)
>  		rfds_mitigation = RFDS_MITIGATION_VERW;
>  
> -	if (x86_arch_cap_msr & ARCH_CAP_RFDS_CLEAR)
> +	if (rfds_has_ucode())
> +		verw_mitigation_selected = true;
> +}

-- 
Josh