Messages in this thread | | | Date | Fri, 28 Jul 2023 16:01:45 -0500 | Subject | Re: [PATCH 1/1] tpm: disable hwrng for fTPM on some AMD designs | From | "Limonciello, Mario" <> |
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On 7/28/2023 3:41 PM, Linus Torvalds wrote: > On Thu, 27 Jul 2023 at 10:05, Daniil Stas <daniil.stas@posteo.net> wrote: >> >> Here is the bug report I created: >> https://bugzilla.kernel.org/show_bug.cgi?id=217719 > > Let's just disable the stupid fTPM hwrnd thing. > > Maybe use it for the boot-time "gather entropy from different > sources", but clearly it should *not* be used at runtime. > > Why would anybody use that crud when any machine that has it > supposedly fixed (which apparently didn't turn out to be true after > all) would also have the CPU rdrand instruction that doesn't have the > problem?
It /seems/ to be a separate problem, but yes I agree with your point.
> > If you don't trust the CPU rdrand implementation (and that has had > bugs too - see clear_rdrand_cpuid_bit() and x86_init_rdrand()), why > would you trust the fTPM version that has caused even *more* problems?
That's exactly why I was asking in the kernel bugzilla if something similar gets tripped up by RDRAND.
I've got a patch that tears it out entirely for AMD fTPMs in the bugzilla, but I would prefer to discuss this with BIOS people before going that direction.
> > So I don't see any downside to just saying "that fTPM thing is not > working". Even if it ends up working in the future, there are > alternatives that aren't any worse. > > Linus
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