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random: continually use hwgenerator randomness 

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>
This commit is contained in:
Dominik Brodowski 2022-01-25 21:14:57 +01:00 committed by Jason A. Donenfeld
parent d2a02e3c8b
commit c321e907aa
1 changed files with 6 additions and 4 deletions
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10
drivers/char/random.c
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@ -2205,13 +2205,15 @@ void add_hwgenerator_randomness(const char *buffer, size_t count,
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);
}