linux-kernel - Re: CVE-2024-35802: x86/sev: Fix position dependent variable references in startup code

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Message-ID: <ZlWbKDZh18KHTsgX@tiehlicka>
Date: Tue, 28 May 2024 10:51:52 +0200
From: Michal Hocko <mhocko@...e.com>
To: Nikolay Borisov <nik.borisov@...e.com>
Cc: cve@...nel.org, linux-kernel@...r.kernel.org,
	linux-cve-announce@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: CVE-2024-35802: x86/sev: Fix position dependent variable
 references in startup code

On Thu 23-05-24 14:14:57, Nikolay Borisov wrote:
[...]
> I'd like to dispute this CVE since it doesn't constitute a security related
> bug. Sure, it might crash a SEV guest during boot but it doesn't constitute
> a security issue per-se.

Let me add analysis by Joerg here:
: This is not a security issue. The patch works around clangs compiler behavior
: where it inserts absolute references to kernel addresses. This breaks kernel
: boot because at the time this code runs the kernel still runs direct-mapped and
: needs to rely on RIP-relative addressing only.
: 
: Any breakage there would be detected at early boot of the kernel by a fatal
: crash, which can not be exploited. Also, our kernels are not compiled with
: clang, so from that perspective this is also not an issue for us either.

So this is a functional fix for clang builds.
-- 
Michal Hocko
SUSE Labs