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| author | Dominik Brodowski <linux@dominikbrodowski.net> | 2022-09-04 12:17:53 +0200 |
|---|---|---|
| committer | Jason A. Donenfeld <Jason@zx2c4.com> | 2022-09-23 12:27:57 +0200 |
| commit | 745558f9588551b1fef9609d165e239bce30d3e8 (patch) | |
| tree | 641b7fd47a65ef944ed6c4e782b91a89fce0ee12 /drivers/char | |
| parent | cd4f24ae9404fd31fc461066e57889be3b68641b (diff) | |
| download | linux-745558f9588551b1fef9609d165e239bce30d3e8.tar.gz linux-745558f9588551b1fef9609d165e239bce30d3e8.tar.bz2 linux-745558f9588551b1fef9609d165e239bce30d3e8.zip | |
random: use hwgenerator randomness more frequently at early boot
Mix in randomness from hw-rng sources more frequently during early
boot, approximately once for every rng reseed.
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Diffstat (limited to 'drivers/char')
| -rw-r--r-- | drivers/char/random.c | 22 |
1 files changed, 10 insertions, 12 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index c8cc23515568..16e0c5f6cf2f 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -260,25 +260,23 @@ static void crng_fast_key_erasure(u8 key[CHACHA_KEY_SIZE], } /* - * Return whether the crng seed is considered to be sufficiently old - * that a reseeding is needed. This happens if the last reseeding - * was CRNG_RESEED_INTERVAL ago, or during early boot, at an interval + * Return the interval until the next reseeding, which is normally + * CRNG_RESEED_INTERVAL, but during early boot, it is at an interval * proportional to the uptime. */ -static bool crng_has_old_seed(void) +static unsigned int crng_reseed_interval(void) { static bool early_boot = true; - unsigned long interval = CRNG_RESEED_INTERVAL; if (unlikely(READ_ONCE(early_boot))) { time64_t uptime = ktime_get_seconds(); if (uptime >= CRNG_RESEED_INTERVAL / HZ * 2) WRITE_ONCE(early_boot, false); else - interval = max_t(unsigned int, CRNG_RESEED_START_INTERVAL, - (unsigned int)uptime / 2 * HZ); + return max_t(unsigned int, CRNG_RESEED_START_INTERVAL, + (unsigned int)uptime / 2 * HZ); } - return time_is_before_jiffies(READ_ONCE(base_crng.birth) + interval); + return CRNG_RESEED_INTERVAL; } /* @@ -320,7 +318,7 @@ static void crng_make_state(u32 chacha_state[CHACHA_STATE_WORDS], * If the base_crng is old enough, we reseed, which in turn bumps the * generation counter that we check below. */ - if (unlikely(crng_has_old_seed())) + if (unlikely(time_is_before_jiffies(READ_ONCE(base_crng.birth) + crng_reseed_interval()))) crng_reseed(); local_lock_irqsave(&crngs.lock, flags); @@ -866,11 +864,11 @@ void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy) credit_init_bits(entropy); /* - * Throttle writing to once every CRNG_RESEED_INTERVAL, unless - * we're not yet initialized. + * Throttle writing to once every reseed interval, unless we're not yet + * initialized. */ if (!kthread_should_stop() && crng_ready()) - schedule_timeout_interruptible(CRNG_RESEED_INTERVAL); + schedule_timeout_interruptible(crng_reseed_interval()); } EXPORT_SYMBOL_GPL(add_hwgenerator_randomness); |