linux-kernel - Re: [PATCH v5 16/16] x86/bugs: Restructure SRSO 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: <20250429165032.GHaBEDWM8qeeE6nfxI@fat_crate.local>
Date: Tue, 29 Apr 2025 18:50:32 +0200
From: Borislav Petkov <bp@...en8.de>
To: David Kaplan <david.kaplan@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...nel.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
Subject: Re: [PATCH v5 16/16] x86/bugs: Restructure SRSO mitigation

On Fri, Apr 18, 2025 at 11:17:21AM -0500, David Kaplan wrote:
> @@ -2738,130 +2730,80 @@ static void __init srso_select_mitigation(void)
>  {
>  	bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE);

I'll push that init after the return so that it doesn't happen unnecessarily.

> -	if (!boot_cpu_has_bug(X86_BUG_SRSO) ||
> -	    cpu_mitigations_off() ||
> -	    srso_cmd == SRSO_CMD_OFF) {
> -		if (boot_cpu_has(X86_FEATURE_SBPB))
> -			x86_pred_cmd = PRED_CMD_SBPB;
> -		goto out;
> -	}
> +	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
> +		srso_mitigation = SRSO_MITIGATION_NONE;
> +
> +	if (srso_mitigation == SRSO_MITIGATION_NONE)
> +		return;
> +
> +	if (srso_mitigation == SRSO_MITIGATION_AUTO)
> +		srso_mitigation = SRSO_MITIGATION_SAFE_RET;
>  
>  	if (has_microcode) {
>  		/*
>  		 * Zen1/2 with SMT off aren't vulnerable after the right
>  		 * IBPB microcode has been applied.
> -		 *
> -		 * Zen1/2 don't have SBPB, no need to try to enable it here.

Why?

-- 
Regards/Gruss,
    Boris.

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