linux-cve-announce - CVE-2025-68313: x86/CPU/AMD: Add RDSEED fix for Zen5

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Message-ID: <2025121654-CVE-2025-68313-c65d@gregkh>
Date: Tue, 16 Dec 2025 16:39:56 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-68313: x86/CPU/AMD: Add RDSEED fix for Zen5

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

x86/CPU/AMD: Add RDSEED fix for Zen5

There's an issue with RDSEED's 16-bit and 32-bit register output
variants on Zen5 which return a random value of 0 "at a rate inconsistent
with randomness while incorrectly signaling success (CF=1)". Search the
web for AMD-SB-7055 for more detail.

Add a fix glue which checks microcode revisions.

  [ bp: Add microcode revisions checking, rewrite. ]

The Linux kernel CVE team has assigned CVE-2025-68313 to this issue.


Affected and fixed versions
===========================

	Fixed in 6.12.58 with commit e980de2ff109dacb6d9d3a77f01b27c467115ecb
	Fixed in 6.17.8 with commit 36ff93e66d0efc46e39fab536a9feec968daa766
	Fixed in 6.18 with commit 607b9fb2ce248cc5b633c5949e0153838992c152

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-68313
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	arch/x86/kernel/cpu/amd.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/e980de2ff109dacb6d9d3a77f01b27c467115ecb
	https://git.kernel.org/stable/c/36ff93e66d0efc46e39fab536a9feec968daa766
	https://git.kernel.org/stable/c/607b9fb2ce248cc5b633c5949e0153838992c152