From: Dominik Brodowski linux@dominikbrodowski.net
commit c321e907aa4803d562d6e70ebed9444ad082f953 upstream.
The rngd kernel thread may sleep indefinitely if the entropy count is kept above random_write_wakeup_bits by other entropy sources. To make best use of multiple sources of randomness, mix entropy from hardware RNGs into the pool at least once within CRNG_RESEED_INTERVAL.
Cc: Herbert Xu herbert@gondor.apana.org.au Cc: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Dominik Brodowski linux@dominikbrodowski.net Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/char/random.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -2193,13 +2193,15 @@ void add_hwgenerator_randomness(const ch return; }
- /* Suspend writing if we're above the trickle threshold. + /* Throttle writing if we're above the trickle threshold. * We'll be woken up again once below random_write_wakeup_thresh, - * or when the calling thread is about to terminate. + * when the calling thread is about to terminate, or once + * CRNG_RESEED_INTERVAL has lapsed. */ - wait_event_interruptible(random_write_wait, + wait_event_interruptible_timeout(random_write_wait, !system_wq || kthread_should_stop() || - POOL_ENTROPY_BITS() <= random_write_wakeup_bits); + POOL_ENTROPY_BITS() <= random_write_wakeup_bits, + CRNG_RESEED_INTERVAL); mix_pool_bytes(buffer, count); credit_entropy_bits(entropy); }