Messages in this thread |  | | Date | Sat, 9 Jul 2022 13:30:52 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH random v2] x86/rdrand: Remove "nordrand" flag in favor of "random.trust_cpu" |
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On Sat, Jul 09, 2022 at 12:43:06PM +0200, Jason A. Donenfeld wrote: > The decision of whether or not to trust RDRAND is controlled by the > "random.trust_cpu" boot time parameter or the CONFIG_RANDOM_TRUST_CPU > compile time default. The "nordrand" flag was added during the early > days of RDRAND, when there were worries that merely using its values > could compromise the RNG. However, these days, RDRAND values are not > used directly but always go through the RNG's hash function, making > "nordrand" no longer useful. > > Rather, the correct switch is "random.trust_cpu", which not only handles > the relevant trust issue directly, but also is general to multiple CPU > types, not just x86. > > However, x86 RDRAND does have a history of being occasionally > problematic. Prior, when the kernel would notice something strange, it'd > warn in dmesg and suggest enabling "nordrand". We can improve on that by > making the test a little bit better and then taking the step of > automatically disabling RDRAND if we detect it's problematic. > > Also extend the basic sanity test to RDSEED in addition to RDRAND, and > disable both if either one fails. > > Cc: x86@kernel.org > Cc: Theodore Ts'o <tytso@mit.edu> > Suggested-by: H. Peter Anvin <hpa@zytor.com> > Suggested-by: Borislav Petkov <bp@suse.de> > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> > --- > This is a tip-ish commit, but it relies on the CONFIG_ARCH_RANDOM commit > in the random tree, so I'll take this through the random tree to avoid > conflicts.
Acked-by: Borislav Petkov <bp@suse.de>
-- Regards/Gruss, Boris.
SUSE Software Solutions Germany GmbH GF: Ivo Totev, Andrew Myers, Andrew McDonald, Martje Boudien Moerman (HRB 36809, AG Nürnberg)
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