Messages in this thread | | | Date | Wed, 13 Jul 2022 16:46:15 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH v5] random: remove CONFIG_ARCH_RANDOM |
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On Fri, Jul 08, 2022 at 02:40:32AM +0200, Jason A. Donenfeld wrote: > When RDRAND was introduced, there was much discussion on whether it > should be trusted and how the kernel should handle that. Initially, two > mechanisms cropped up, CONFIG_ARCH_RANDOM, a compile time switch, and > "nordrand", a boot-time switch. > > Later the thinking evolved. With a properly designed RNG, using RDRAND > values alone won't harm anything, even if the outputs are malicious. > Rather, the issue is whether those values are being *trusted* to be good > or not. And so a new set of options were introduced as the real > ones that people use -- CONFIG_RANDOM_TRUST_CPU and "random.trust_cpu". > With these options, RDRAND is used, but it's not always credited. So in > the worst case, it does nothing, and in the best case, maybe it helps. > > Along the way, CONFIG_ARCH_RANDOM's meaning got sort of pulled into the > center and became something certain platforms force-select. > > The old options don't really help with much, and it's a bit odd to have > special handling for these instructions when the kernel can deal fine > with the existence or untrusted existence or broken existence or > non-existence of that CPU capability. > > Simplify the situation by removing CONFIG_ARCH_RANDOM and using the > ordinary asm-generic fallback pattern instead, keeping the two options > that are actually used. For now it leaves "nordrand" for now, as the > removal of that will take a different route. > > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Alexander Gordeev <agordeev@linux.ibm.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: H. Peter Anvin <hpa@zytor.com> > Acked-by: Borislav Petkov <bp@suse.de> > Acked-by: Heiko Carstens <hca@linux.ibm.com> > Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
For arm64:
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
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