diff options
| -rw-r--r-- | drivers/char/random.c | 28 |
1 files changed, 25 insertions, 3 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 19a602c69f2f..defdba110d1d 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -328,6 +328,28 @@ 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 might be attempted. This happens if the last + * reseeding was CRNG_RESEED_INTERVAL ago, or during early boot, at + * an interval proportional to the uptime. + */ +static bool crng_has_old_seed(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, 5 * HZ, + (unsigned int)uptime / 2 * HZ); + } + return time_after(jiffies, READ_ONCE(base_crng.birth) + interval); +} + +/* * This function returns a ChaCha state that you may use for generating * random data. It also returns up to 32 bytes on its own of random data * that may be used; random_data_len may not be greater than 32. @@ -360,10 +382,10 @@ static void crng_make_state(u32 chacha_state[CHACHA_STATE_WORDS], } /* - * If the base_crng is more than 5 minutes old, we reseed, which - * in turn bumps the generation counter that we check below. + * If the base_crng is old enough, we try to reseed, which in turn + * bumps the generation counter that we check below. */ - if (unlikely(time_after(jiffies, READ_ONCE(base_crng.birth) + CRNG_RESEED_INTERVAL))) + if (unlikely(crng_has_old_seed())) crng_reseed(false); local_lock_irqsave(&crngs.lock, flags); |