diff options
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/char/random.c | 91 |
1 files changed, 21 insertions, 70 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 882f78829a24..9014fd54da64 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -289,12 +289,14 @@ enum poolinfo { POOL_BITS = BLAKE2S_HASH_SIZE * 8, POOL_BITSHIFT = ilog2(POOL_BITS), + POOL_MIN_BITS = POOL_BITS / 2, /* To allow fractional bits to be tracked, the entropy_count field is * denominated in units of 1/8th bits. */ POOL_ENTROPY_SHIFT = 3, #define POOL_ENTROPY_BITS() (input_pool.entropy_count >> POOL_ENTROPY_SHIFT) - POOL_FRACBITS = POOL_BITS << POOL_ENTROPY_SHIFT + POOL_FRACBITS = POOL_BITS << POOL_ENTROPY_SHIFT, + POOL_MIN_FRACBITS = POOL_MIN_BITS << POOL_ENTROPY_SHIFT }; /* @@ -375,8 +377,7 @@ static struct { .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), }; -static bool extract_entropy(void *buf, size_t nbytes, int min); -static void _extract_entropy(void *buf, size_t nbytes); +static void extract_entropy(void *buf, size_t nbytes); static void crng_reseed(struct crng_state *crng, bool use_input_pool); @@ -467,7 +468,7 @@ static void process_random_ready_list(void) */ static void credit_entropy_bits(int nbits) { - int entropy_count, entropy_bits, orig; + int entropy_count, orig; int nfrac = nbits << POOL_ENTROPY_SHIFT; /* Ensure that the multiplication can avoid being 64 bits wide. */ @@ -527,8 +528,7 @@ retry: trace_credit_entropy_bits(nbits, entropy_count >> POOL_ENTROPY_SHIFT, _RET_IP_); - entropy_bits = entropy_count >> POOL_ENTROPY_SHIFT; - if (crng_init < 2 && entropy_bits >= 128) + if (crng_init < 2 && entropy_count >= POOL_MIN_FRACBITS) crng_reseed(&primary_crng, true); } @@ -618,7 +618,7 @@ static void crng_initialize_secondary(struct crng_state *crng) static void __init crng_initialize_primary(void) { - _extract_entropy(&primary_crng.state[4], sizeof(u32) * 12); + extract_entropy(&primary_crng.state[4], sizeof(u32) * 12); if (crng_init_try_arch_early() && trust_cpu && crng_init < 2) { invalidate_batched_entropy(); numa_crng_init(); @@ -788,8 +788,17 @@ static void crng_reseed(struct crng_state *crng, bool use_input_pool) } buf; if (use_input_pool) { - if (!extract_entropy(&buf, 32, 16)) - return; + int entropy_count; + do { + entropy_count = READ_ONCE(input_pool.entropy_count); + if (entropy_count < POOL_MIN_FRACBITS) + return; + } while (cmpxchg(&input_pool.entropy_count, entropy_count, 0) != entropy_count); + extract_entropy(buf.key, sizeof(buf.key)); + if (random_write_wakeup_bits) { + wake_up_interruptible(&random_write_wait); + kill_fasync(&fasync, SIGIO, POLL_OUT); + } } else { _extract_crng(&primary_crng, buf.block); _crng_backtrack_protect(&primary_crng, buf.block, @@ -1115,51 +1124,10 @@ EXPORT_SYMBOL_GPL(add_disk_randomness); *********************************************************************/ /* - * This function decides how many bytes to actually take from the - * given pool, and also debits the entropy count accordingly. - */ -static size_t account(size_t nbytes, int min) -{ - int entropy_count, orig; - size_t ibytes, nfrac; - - BUG_ON(input_pool.entropy_count > POOL_FRACBITS); - - /* Can we pull enough? */ -retry: - entropy_count = orig = READ_ONCE(input_pool.entropy_count); - if (WARN_ON(entropy_count < 0)) { - pr_warn("negative entropy count: count %d\n", entropy_count); - entropy_count = 0; - } - - /* never pull more than available */ - ibytes = min_t(size_t, nbytes, entropy_count >> (POOL_ENTROPY_SHIFT + 3)); - if (ibytes < min) - ibytes = 0; - nfrac = ibytes << (POOL_ENTROPY_SHIFT + 3); - if ((size_t)entropy_count > nfrac) - entropy_count -= nfrac; - else - entropy_count = 0; - - if (cmpxchg(&input_pool.entropy_count, orig, entropy_count) != orig) - goto retry; - - trace_debit_entropy(8 * ibytes); - if (ibytes && POOL_ENTROPY_BITS() < random_write_wakeup_bits) { - wake_up_interruptible(&random_write_wait); - kill_fasync(&fasync, SIGIO, POLL_OUT); - } - - return ibytes; -} - -/* * This is an HKDF-like construction for using the hashed collected entropy * as a PRF key, that's then expanded block-by-block. */ -static void _extract_entropy(void *buf, size_t nbytes) +static void extract_entropy(void *buf, size_t nbytes) { unsigned long flags; u8 seed[BLAKE2S_HASH_SIZE], next_key[BLAKE2S_HASH_SIZE]; @@ -1169,6 +1137,8 @@ static void _extract_entropy(void *buf, size_t nbytes) } block; size_t i; + trace_extract_entropy(nbytes, POOL_ENTROPY_BITS()); + for (i = 0; i < ARRAY_SIZE(block.rdrand); ++i) { if (!arch_get_random_long(&block.rdrand[i])) block.rdrand[i] = random_get_entropy(); @@ -1200,25 +1170,6 @@ static void _extract_entropy(void *buf, size_t nbytes) memzero_explicit(&block, sizeof(block)); } -/* - * This function extracts randomness from the "entropy pool", and - * returns it in a buffer. - * - * The min parameter specifies the minimum amount we can pull before - * failing to avoid races that defeat catastrophic reseeding. If we - * have less than min entropy available, we return false and buf is - * not filled. - */ -static bool extract_entropy(void *buf, size_t nbytes, int min) -{ - trace_extract_entropy(nbytes, POOL_ENTROPY_BITS(), _RET_IP_); - if (account(nbytes, min)) { - _extract_entropy(buf, nbytes); - return true; - } - return false; -} - #define warn_unseeded_randomness(previous) \ _warn_unseeded_randomness(__func__, (void *)_RET_IP_, (previous)) |