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Date: Fri, 19 Jan 2024 07:58:28 +0300
From: kirill.shutemov@linux.intel.com
To: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
	"H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org,
	daniel.sneddon@linux.intel.com,
	antonio.gomez.iglesias@linux.intel.com, rick.p.edgecombe@intel.com,
	sohil.mehta@intel.com, alexander.shishkin@intel.com
Subject: Re: [PATCH] x86/lam: Disable ADDRESS_MASKING in most cases
Message-ID: <20240119045828.xcypcr32cpovqptg@box.shutemov.name>
References: <919b6370a908bb091779ec2eca7ca5e369d57847.1705631230.git.pawan.kumar.gupta@linux.intel.com>
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In-Reply-To: <919b6370a908bb091779ec2eca7ca5e369d57847.1705631230.git.pawan.kumar.gupta@linux.intel.com>

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@vger.kernel.org # v6.4+
> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>

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

-- 
  Kiryl Shutsemau / Kirill A. Shutemov