linux-kernel - Re: [tip: x86/urgent] x86/CPU/AMD: Add RDSEED fix for Zen5

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <aSTZylJfiN5uXDi1@duo.ucw.cz>
Date: Mon, 24 Nov 2025 23:18:50 +0100
From: Pavel Machek <pavel@....cz>
To: Peter Jung <ptr1337@...hyos.org>
Cc: linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org,
	stable@...r.kernel.org, Gregory Price <gourry@...rry.net>,
	"Borislav Petkov (AMD)" <bp@...en8.de>, x86@...nel.org
Subject: Re: [tip: x86/urgent] x86/CPU/AMD: Add RDSEED fix for Zen5

Hi!

> > Add a fix glue which checks microcode revisions.
> > 
> >    [ bp: Add microcode revisions checking, rewrite. ]
> > 
> > Cc:stable@...r.kernel.org
> > Signed-off-by: Gregory Price<gourry@...rry.net>
> > Signed-off-by: Borislav Petkov (AMD)<bp@...en8.de>
> > Link:https://lore.kernel.org/r/20251018024010.4112396-1-gourry@gourry.net
> > ---
> >   arch/x86/kernel/cpu/amd.c | 10 ++++++++++
> >   1 file changed, 10 insertions(+)
> > 
> > diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> > index ccaa51c..bc29be6 100644
> > --- a/arch/x86/kernel/cpu/amd.c
> > +++ b/arch/x86/kernel/cpu/amd.c
> > @@ -1035,8 +1035,18 @@ static void init_amd_zen4(struct cpuinfo_x86 *c)
> >   	}
> >   }
> > +static const struct x86_cpu_id zen5_rdseed_microcode[] = {
> > +	ZEN_MODEL_STEP_UCODE(0x1a, 0x02, 0x1, 0x0b00215a),
> > +	ZEN_MODEL_STEP_UCODE(0x1a, 0x11, 0x0, 0x0b101054),
> > +};
> > +

> This fix seems to break quite a bunch of users in CachyOS. There has been
> now several users reporting that there system can not get properly into the
> graphical interface.
> 
> CachyOS is compiling the packages with -march=znver5 and the GCC compiler
> currently does pass RDSEED.

Besides other things, GCC should probably be fixed not to do that.

And this will be fun for both mainline and -stable: security bug or
broken boot, pick one :-(.

Best regards,
								Pavel
-- 
I don't work for Nazis and criminals, and neither should you.
Boycott Putin, Trump, Netanyahu and Musk!

Download attachment "signature.asc" of type "application/pgp-signature" (196 bytes)