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random: credit architectural init the exact amount 

RDRAND and RDSEED can fail sometimes, which is fine. We currently
initialize the RNG with 512 bits of RDRAND/RDSEED. We only need 256 bits
of those to succeed in order to initialize the RNG. Instead of the
current "all or nothing" approach, actually credit these contributions
the amount that is actually contributed.

Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jason A. Donenfeld 2022-05-12 15:32:26 +02:00
parent 2f14062bb1
commit 12e45a2a63
1 changed files with 6 additions and 6 deletions
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12
drivers/char/random.c
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@ -927,9 +927,8 @@ static struct notifier_block pm_notifier = { .notifier_call = random_pm_notifica
*/
int __init random_init(const char *command_line)
{
size_t i;
ktime_t now = ktime_get_real();
bool arch_init = true;
unsigned int i, arch_bytes;
unsigned long rv;
#if defined(LATENT_ENTROPY_PLUGIN)
@ -937,11 +936,12 @@ int __init random_init(const char *command_line)
_mix_pool_bytes(compiletime_seed, sizeof(compiletime_seed));
#endif
for (i = 0; i < BLAKE2S_BLOCK_SIZE; i += sizeof(rv)) {
for (i = 0, arch_bytes = BLAKE2S_BLOCK_SIZE;
i < BLAKE2S_BLOCK_SIZE; i += sizeof(rv)) {
if (!arch_get_random_seed_long_early(&rv) &&
!arch_get_random_long_early(&rv)) {
rv = random_get_entropy();
arch_init = false;
arch_bytes -= sizeof(rv);
}
_mix_pool_bytes(&rv, sizeof(rv));
}
@ -952,8 +952,8 @@ int __init random_init(const char *command_line)
if (crng_ready())
crng_reseed();
else if (arch_init && trust_cpu)
credit_init_bits(BLAKE2S_BLOCK_SIZE * 8);
else if (trust_cpu)
credit_init_bits(arch_bytes * 8);
WARN_ON(register_pm_notifier(&pm_notifier));