From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932903Ab2JAXBU (ORCPT ); Mon, 1 Oct 2012 19:01:20 -0400 Received: from 1wt.eu ([62.212.114.60]:35318 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932864Ab2JAXBN (ORCPT ); Mon, 1 Oct 2012 19:01:13 -0400 Message-Id: <20121001225204.519792971@1wt.eu> User-Agent: quilt/0.48-1 Date: Tue, 02 Oct 2012 00:54:40 +0200 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "David S. Miller" , "Theodore Tso" , Herbert Xu , Matt Mackall , Tony Luck , Eric Dumazet , "H. Peter Anvin" , Paul Gortmaker , Willy Tarreau Subject: [ 163/180] random: Use arch_get_random_int instead of cycle counter if avail In-Reply-To: <6a854f579a99b4fe2efaca1057e8ae22@local> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-longterm review patch. If anyone has any objections, please let me know. ------------------ From: Linus Torvalds commit cf833d0b9937874b50ef2867c4e8badfd64948ce upstream. We still don't use rdrand in /dev/random, which just seems stupid. We accept the *cycle*counter* as a random input, but we don't accept rdrand? That's just broken. Sure, people can do things in user space (write to /dev/random, use rdrand in addition to /dev/random themselves etc etc), but that *still* seems to be a particularly stupid reason for saying "we shouldn't bother to try to do better in /dev/random". And even if somebody really doesn't trust rdrand as a source of random bytes, it seems singularly stupid to trust the cycle counter *more*. So I'd suggest the attached patch. I'm not going to even bother arguing that we should add more bits to the entropy estimate, because that's not the point - I don't care if /dev/random fills up slowly or not, I think it's just stupid to not use the bits we can get from rdrand and mix them into the strong randomness pool. Link: http://lkml.kernel.org/r/CA%2B55aFwn59N1=m651QAyTy-1gO1noGbK18zwKDwvwqnravA84A@mail.gmail.com Acked-by: "David S. Miller" Acked-by: "Theodore Ts'o" Acked-by: Herbert Xu Cc: Matt Mackall Cc: Tony Luck Cc: Eric Dumazet Signed-off-by: H. Peter Anvin Signed-off-by: Paul Gortmaker Signed-off-by: Willy Tarreau --- drivers/char/random.c | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index f2a1651..ac74029 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -624,8 +624,8 @@ static struct timer_rand_state input_timer_state; static void add_timer_randomness(struct timer_rand_state *state, unsigned num) { struct { - cycles_t cycles; long jiffies; + unsigned cycles; unsigned num; } sample; long delta, delta2, delta3; @@ -637,7 +637,11 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num) goto out; sample.jiffies = jiffies; - sample.cycles = get_cycles(); + + /* Use arch random value, fall back to cycles */ + if (!arch_get_random_int(&sample.cycles)) + sample.cycles = get_cycles(); + sample.num = num; mix_pool_bytes(&input_pool, &sample, sizeof(sample)); -- 1.7.2.1.45.g54fbc