diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2011-12-22 11:36:22 -0800 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2012-08-10 00:24:39 +0100 |
| commit | e50d73fccd7e6f9a9f902b58620fc286195a4a1c (patch) | |
| tree | 187076c0c3af4fce06c6b6f4ea6cc0fc9eb1cf3a /drivers/char | |
| parent | bab9409a251e351bf1a2c1c62cdad22691f32668 (diff) | |
random: Use arch_get_random_int instead of cycle counter if avail
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@davemloft.net>
Acked-by: "Theodore Ts'o" <tytso@mit.edu>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'drivers/char')
| -rw-r--r-- | 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 6035ab8d5ef7..85da8740586b 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)); |