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Message-ID: <20140722135915.GB25291@thunk.org> Date: Tue, 22 Jul 2014 09:59:15 -0400 From: Theodore Ts'o <tytso@....edu> To: Andy Lutomirski <luto@...capital.net> Cc: kvm@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>, x86@...nel.org, Daniel Borkmann <dborkman@...hat.com>, Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>, Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>, Gleb Natapov <gleb@...nel.org>, Paolo Bonzini <pbonzini@...hat.com>, bsd@...hat.com, Andrew Honig <ahonig@...gle.com> Subject: Re: [PATCH v4 2/5] random: Add and use arch_get_rng_seed On Thu, Jul 17, 2014 at 11:22:17AM -0700, Andy Lutomirski wrote: > Currently, init_std_data contains its own logic for using arch > random sources. This logic is a bit strange: it reads one long of > arch random data per byte of internal state. This isn't true. Check out the init_std_data() a bit more closely. unsigned long rv; ... for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) { ... In particular, note the "i -= sizeof(rv)". We are reading one bit per bit of internal state beeing seeded. > Assuming the arch sources are perfect, this is the right thing to > do. They're not, though, so the followup patch attempts to > implement the correct logic on x86. ... and that's not a problem because we aren't giving any entropy credit --- and this is deliberate, because we don't want to trust un-auditable hardware. We are deliberately trying to be conservative here. So I don't think either this patch or the next one is needed. It adds far more complexity than is warranted. Regards, - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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