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Commit 087a14b9 authored by Jason A. Donenfeld's avatar Jason A. Donenfeld Committed by Greg Kroah-Hartman
Browse files

random: credit architectural init the exact amount 



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: default avatarDominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: default avatarJason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ac48f7be

drivers/char/random.c

+6 −6
Original line number Diff line number Diff line
@@ -891,9 +891,8 @@ 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)
@@ -901,11 +900,12 @@ 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));

	}
@@ -916,8 +916,8 @@ 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;

}