linux-kernel - Re: [PATCH v10 04/15] x86/cpu: Set LASS CR4 bit as pinning sensitive

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Message-ID: <e873d2b06a18b69e246f8011c556259d21c7e022.camel@intel.com>
Date: Tue, 7 Oct 2025 18:24:04 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "Mehta, Sohil" <sohil.mehta@...el.com>, "tglx@...utronix.de"
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Subject: Re: [PATCH v10 04/15] x86/cpu: Set LASS CR4 bit as pinning sensitive

On Mon, 2025-10-06 at 23:51 -0700, Sohil Mehta wrote:
> From: Yian Chen <yian.chen@...el.com>
> 
> Security features such as LASS are not expected to be disabled once
> initialized. Add LASS to the CR4 pinned mask.
> 
> Signed-off-by: Yian Chen <yian.chen@...el.com>
> Signed-off-by: Sohil Mehta <sohil.mehta@...el.com>

I was debating whether we really need this, given the LASS and CR pinning threat
models. CR pinning seems to be about after an attacker has already hijacked a
control flow and is looking to escalate it into more control. We could maybe get
away with dropping this and the following patch. But it would still be good to
get a warning if it gets turned off inadvertently I think. It might be worth
adding justification like that to the log.