From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Theodore Ts'o <tytso@mit.edu>
Cc: Tom Lendacky <thomas.lendacky@amd.com>,
"Reshetova, Elena" <elena.reshetova@intel.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
"x86@kernel.org" <x86@kernel.org>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com>,
"Nakajima, Jun" <jun.nakajima@intel.com>,
"Kalra, Ashish" <ashish.kalra@amd.com>,
Sean Christopherson <seanjc@google.com>,
"linux-coco@lists.linux.dev" <linux-coco@lists.linux.dev>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] x86/random: Retry on RDSEED failure
Date: Thu, 15 Feb 2024 14:01:04 +0100 [thread overview]
Message-ID: <Zc4LEAOCFOBcIRXy@zx2c4.com> (raw)
In-Reply-To: <20240214201103.GD394352@mit.edu>
On Wed, Feb 14, 2024 at 03:11:03PM -0500, Theodore Ts'o wrote:
> On Wed, Feb 14, 2024 at 09:04:34PM +0100, Jason A. Donenfeld wrote:
> > AMD people, Intel people: what are the fullest statements we can rely
> > on here? Do the following two statements work?
> >
> > 1) On newer chips, RDRAND never fails.
> > 2) On older chips, RDRAND never fails if you try 10 times in a loop,
> > unless you consider host->guest attacks, which we're not, because CoCo
> > is only a thing on the newer chips.
> >
> > If those hold true, then the course of action would be to just add a
> > WARN_ON(!ok) but keep the loop as-is.
>
> I think we may only want to do the WARN_ON in early boot. Otherwise,
> on older chips, if a userspace process executes RDRAND is a tight
> loop, it might cause the WARN_ON to trigger, which is considered
> undesirable (and is certainly going to be something that could result
> in a syzbot complaint).
Yea, seems reasonable. Or maybe we just don't bother adding any WARN
there and just address the CoCo thing with the patch 2/2. As it turns
out, on normal systems, the RNG is designed anyway to deal with a broken
or missing RDRAND. So maybe adding these heuristics to warn when the CPU
is broken isn't worth it? Or maybe that's an interesting thing to do?
Dunno, I'm indifferent about it I suppose. But I agree if it's added,
doing it at early boot only makes most sense.
Jason
next prev parent reply other threads:[~2024-02-15 13:01 UTC|newest]
Thread overview: 99+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-30 8:30 [PATCH 1/2] x86/random: Retry on RDSEED failure Kirill A. Shutemov
2024-01-30 8:30 ` [PATCH 2/2] x86/random: Issue a warning if RDRAND or RDSEED fails Kirill A. Shutemov
2024-01-30 12:37 ` Jason A. Donenfeld
2024-01-30 13:45 ` Reshetova, Elena
2024-01-30 14:21 ` Jason A. Donenfeld
2024-01-30 14:55 ` Reshetova, Elena
2024-01-30 15:00 ` Jason A. Donenfeld
2024-01-30 17:31 ` Dave Hansen
2024-01-30 17:49 ` Jason A. Donenfeld
2024-01-30 17:58 ` Dave Hansen
2024-01-30 18:15 ` H. Peter Anvin
2024-01-30 18:23 ` Jason A. Donenfeld
2024-01-30 18:23 ` Jason A. Donenfeld
2024-01-30 18:37 ` Dave Hansen
2024-01-30 18:05 ` Daniel P. Berrangé
2024-01-30 18:24 ` Jason A. Donenfeld
2024-01-30 18:31 ` Jason A. Donenfeld
2024-01-30 18:40 ` H. Peter Anvin
2024-01-31 8:16 ` Reshetova, Elena
2024-01-31 11:59 ` Dr. Greg
2024-01-31 13:06 ` Jason A. Donenfeld
2024-01-31 18:02 ` Reshetova, Elena
2024-01-31 20:35 ` Dr. Greg
2024-02-01 4:47 ` Theodore Ts'o
2024-02-01 9:54 ` Dr. Greg
2024-02-01 11:08 ` Daniel P. Berrangé
2024-02-01 21:04 ` Dr. Greg
2024-02-02 7:56 ` Reshetova, Elena
2024-02-01 7:26 ` Reshetova, Elena
2024-02-01 10:52 ` Dr. Greg
2024-02-06 1:12 ` Dr. Greg
2024-02-06 8:04 ` Daniel P. Berrangé
2024-02-06 12:04 ` Dr. Greg
2024-02-06 13:00 ` Daniel P. Berrangé
2024-02-08 10:31 ` Dr. Greg
2024-02-06 13:50 ` Daniel P. Berrangé
2024-02-06 15:35 ` Borislav Petkov
2024-02-08 11:44 ` Dr. Greg
2024-02-09 17:31 ` Borislav Petkov
2024-02-09 19:49 ` Jason A. Donenfeld
2024-02-09 20:37 ` Dave Hansen
2024-02-09 21:45 ` Borislav Petkov
2024-02-06 18:49 ` H. Peter Anvin
2024-02-08 16:38 ` Dr. Greg
2024-01-30 15:50 ` Kuppuswamy Sathyanarayanan
2024-01-30 12:29 ` [PATCH 1/2] x86/random: Retry on RDSEED failure Jason A. Donenfeld
2024-01-30 12:51 ` Jason A. Donenfeld
2024-01-30 13:10 ` Reshetova, Elena
2024-01-30 14:06 ` Jason A. Donenfeld
2024-01-30 14:43 ` Daniel P. Berrangé
2024-01-30 15:12 ` Jason A. Donenfeld
2024-01-30 18:35 ` Jason A. Donenfeld
2024-01-30 19:06 ` Reshetova, Elena
2024-01-30 19:16 ` Jason A. Donenfeld
2024-01-31 7:56 ` Reshetova, Elena
2024-01-31 13:14 ` Jason A. Donenfeld
2024-01-31 14:07 ` Theodore Ts'o
2024-01-31 14:45 ` Jason A. Donenfeld
2024-01-31 14:52 ` Jason A. Donenfeld
2024-01-31 17:10 ` Theodore Ts'o
2024-01-31 17:37 ` Reshetova, Elena
2024-01-31 18:01 ` Jason A. Donenfeld
2024-02-01 4:57 ` Theodore Ts'o
2024-02-01 18:09 ` Jason A. Donenfeld
2024-02-01 18:46 ` Dave Hansen
2024-02-01 19:02 ` H. Peter Anvin
2024-02-02 7:25 ` Reshetova, Elena
2024-02-02 15:39 ` Theodore Ts'o
2024-02-03 10:12 ` Jason A. Donenfeld
2024-02-09 19:53 ` Jason A. Donenfeld
2024-02-12 8:25 ` Reshetova, Elena
2024-02-12 16:32 ` Theodore Ts'o
2024-02-13 7:28 ` Dan Williams
2024-02-13 23:13 ` Theodore Ts'o
2024-02-14 0:53 ` Dan Williams
2024-02-14 4:32 ` Theodore Ts'o
2024-02-14 6:48 ` Dan Williams
2024-02-14 6:54 ` Reshetova, Elena
2024-02-14 8:34 ` Nikolay Borisov
2024-02-14 9:34 ` Dr. Greg
2024-02-14 17:30 ` Jason A. Donenfeld
2024-02-14 15:18 ` Reshetova, Elena
2024-02-14 17:21 ` Jason A. Donenfeld
2024-02-14 17:59 ` Reshetova, Elena
2024-02-14 19:32 ` Jason A. Donenfeld
2024-02-15 7:07 ` Reshetova, Elena
2024-02-15 12:58 ` Jason A. Donenfeld
2024-02-14 19:46 ` Tom Lendacky
2024-02-14 20:04 ` Jason A. Donenfeld
2024-02-14 20:11 ` Theodore Ts'o
2024-02-15 13:01 ` Jason A. Donenfeld [this message]
2024-02-14 20:14 ` Dave Hansen
2024-02-02 15:47 ` James Bottomley
2024-02-02 16:05 ` Theodore Ts'o
2024-02-02 21:28 ` James Bottomley
2024-02-03 14:35 ` Theodore Ts'o
2024-02-06 19:12 ` H. Peter Anvin
2024-01-30 15:20 ` H. Peter Anvin
2024-01-30 15:44 ` Kuppuswamy Sathyanarayanan
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