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random: credit architectural init the exact amount

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commit 12e45a2a6308105469968951e6d563e8f4fea187 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jason A. Donenfeld 2022-05-12 15:32:26 +02:00 committed by Greg Kroah-Hartman
parent 11cce5040c
commit 4e5e6754a4
1 changed files with 6 additions and 6 deletions
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12
drivers/char/random.c
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@ -896,9 +896,8 @@ early_param("random.trust_bootloader", parse_trust_bootloader);
*/
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)
@ -906,11 +905,12 @@ 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));
}
@ -921,8 +921,8 @@ 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);
return 0;
}