From: Greg KH <gre...@linuxfoundation.org> 3.0-stable review patch. If anyone has any objections, please let me know.
------------------ From: Linus Torvalds <torva...@linux-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-1go1nogbk18zwkdwvwqnrava...@mail.gmail.com Acked-by: "David S. Miller" <da...@davemloft.net> Acked-by: "Theodore Ts'o" <ty...@mit.edu> Acked-by: Herbert Xu <herb...@gondor.apana.org.au> Cc: Matt Mackall <m...@selenic.com> Cc: Tony Luck <tony.l...@intel.com> Cc: Eric Dumazet <eric.duma...@gmail.com> Signed-off-by: H. Peter Anvin <h...@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- drivers/char/random.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -624,8 +624,8 @@ static struct timer_rand_state input_tim 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 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)); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
