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random: credit architectural init the exact amount

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commit 12e45a2a63 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 Chris
parent c901c7cf3a
commit 17b72df2e5
1 changed files with 6 additions and 6 deletions
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12
drivers/char/random.c
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@@ -892,9 +892,8 @@ 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)
@@ -902,11 +901,12 @@ 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));
}
@@ -917,8 +917,8 @@ 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;
}