linux-kernel - Re: [PATCH 13/14] x86: BHI stubs

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Message-ID: <CAKUFkX03dmRL9Kk0=OLjyB0+FAx6rGXAHke4Y-NVD0au01qkNg@mail.gmail.com>
Date: Mon, 28 Oct 2024 22:59:56 -0700
From: Joao Moreira <joao@...rdrivepizza.com>
To: "Constable, Scott D" <scott.d.constable@...el.com>
Cc: "andrew.cooper3@...rix.com" <andrew.cooper3@...rix.com>, Peter Zijlstra <peterz@...radead.org>, 
	Josh Poimboeuf <jpoimboe@...nel.org>, "x86@...nel.org" <x86@...nel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Milburn, Alyssa" <alyssa.milburn@...el.com>, 
	"jose.marchesi@...cle.com" <jose.marchesi@...cle.com>, "hjl.tools@...il.com" <hjl.tools@...il.com>, 
	"ndesaulniers@...gle.com" <ndesaulniers@...gle.com>, 
	"samitolvanen@...gle.com" <samitolvanen@...gle.com>, "nathan@...nel.org" <nathan@...nel.org>, 
	"ojeda@...nel.org" <ojeda@...nel.org>, "kees@...nel.org" <kees@...nel.org>, 
	"alexei.starovoitov@...il.com" <alexei.starovoitov@...il.com>
Subject: Re: [PATCH 13/14] x86: BHI stubs

On Mon, Oct 21, 2024 at 8:06 AM Constable, Scott D
<scott.d.constable@...el.com> wrote:
>
> Hello Andrew,
>
> My understanding of the FineIBT approach is that the hash values are not intended to be secret, and therefore leaking these hash values would not expose a new risk. Joao is also on this thread and knows a lot more about FineIBT than I do, so he can chime in if my reasoning is unsound.

Technically the hashes are not a secret indeed. With that said, I
think it was Kees who submitted a patch that randomizes the hash
values at boot time, as a security in depth / probabilistic measure
against an attacker being able to generate executable valid targets.

Tks,
Joao