Messages in this thread | | | Date | Wed, 14 Feb 2024 15:11:03 -0500 | From | "Theodore Ts'o" <> | Subject | Re: [PATCH 1/2] x86/random: Retry on RDSEED failure |
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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).
- Ted
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