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Message-Id: <20121001225204.519792971@1wt.eu>
Date: Tue, 02 Oct 2012 00:54:40 +0200
From: Willy Tarreau <w@....eu>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
"Theodore Tso" <tytso@....edu>,
Herbert Xu <herbert@...dor.hengli.com.au>,
Matt Mackall <mpm@...enic.com>,
Tony Luck <tony.luck@...el.com>,
Eric Dumazet <eric.dumazet@...il.com>,
"H. Peter Anvin" <hpa@...ux.intel.com>,
Paul Gortmaker <paul.gortmaker@...driver.com>,
Willy Tarreau <w@....eu>
Subject: [ 163/180] random: Use arch_get_random_int instead of cycle counter if avail
2.6.32-longterm review patch. If anyone has any objections, please let me know.
------------------
From: Linus Torvalds <torvalds@...ux-foundation.org>
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" <davem@...emloft.net>
Acked-by: "Theodore Ts'o" <tytso@....edu>
Acked-by: Herbert Xu <herbert@...dor.apana.org.au>
Cc: Matt Mackall <mpm@...enic.com>
Cc: Tony Luck <tony.luck@...el.com>
Cc: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
Signed-off-by: Willy Tarreau <w@....eu>
---
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
--
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