linux-kernel - Re: [PATCH] x86/lam: Disable ADDRESS

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Date: Fri, 19 Jan 2024 07:58:28 +0300
From: kirill.shutemov@...ux.intel.com
To: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	daniel.sneddon@...ux.intel.com,
	antonio.gomez.iglesias@...ux.intel.com, rick.p.edgecombe@...el.com,
	sohil.mehta@...el.com, alexander.shishkin@...el.com
Subject: Re: [PATCH] x86/lam: Disable ADDRESS_MASKING in most cases

On Thu, Jan 18, 2024 at 06:35:47PM -0800, Pawan Gupta wrote:
> Intel feature Linear Address Masking (LAM) has a weakness related to
> transient execution as described in the SLAM paper[1]. Unless Linear
> Address Space Separation (LASS) is enabled this weakness may be
> exploitable.
> 
> Until kernel adds support for LASS[2], only allow LAM for COMPILE_TEST,
> or when speculation mitigations have been disabled at compile time,
> otherwise keep LAM disabled.
> 

It worth adding that there's no HW on market that supports LAM, so nobody
affected by the issue.

> [1] SLAM: https://download.vusec.net/papers/slam_sp24.pdf
> [2] LASS: https://lore.kernel.org/lkml/20230609183632.48706-1-alexander.shishkin@linux.intel.com/
> 
> Cc: stable@...r.kernel.org # v6.4+
> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>

Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov