From: "Jason A. Donenfeld" Jason@zx2c4.com
commit 0791e8b655cc373718f0f58800fdc625a3447ac5 upstream.
Now that we have an explicit base_crng generation counter, we don't need a separate one for batched entropy. Rather, we can just move the generation forward every time we change crng_init state or update the base_crng key.
Cc: Theodore Ts'o tytso@mit.edu Reviewed-by: Eric Biggers ebiggers@google.com 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 --- drivers/char/random.c | 29 ++++++++--------------------- 1 file changed, 8 insertions(+), 21 deletions(-)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -430,8 +430,6 @@ static DEFINE_PER_CPU(struct crng, crngs
static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
-static void invalidate_batched_entropy(void); - /* * crng_fast_load() can be called by code in the interrupt service * path. So we can't afford to dilly-dally. Returns the number of @@ -454,7 +452,7 @@ static size_t crng_fast_load(const void src++; crng_init_cnt++; len--; ret++; } if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) { - invalidate_batched_entropy(); + ++base_crng.generation; crng_init = 1; } spin_unlock_irqrestore(&base_crng.lock, flags); @@ -531,7 +529,6 @@ static void crng_reseed(void) WRITE_ONCE(base_crng.generation, next_gen); WRITE_ONCE(base_crng.birth, jiffies); if (crng_init < 2) { - invalidate_batched_entropy(); crng_init = 2; finalize_init = true; } @@ -1256,8 +1253,9 @@ int __init rand_initialize(void) mix_pool_bytes(utsname(), sizeof(*(utsname())));
extract_entropy(base_crng.key, sizeof(base_crng.key)); + ++base_crng.generation; + if (arch_init && trust_cpu && crng_init < 2) { - invalidate_batched_entropy(); crng_init = 2; pr_notice("crng init done (trusting CPU's manufacturer)\n"); } @@ -1597,8 +1595,6 @@ struct ctl_table random_table[] = { }; #endif /* CONFIG_SYSCTL */
-static atomic_t batch_generation = ATOMIC_INIT(0); - struct batched_entropy { union { /* @@ -1612,8 +1608,8 @@ struct batched_entropy { u32 entropy_u32[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(u32))]; }; local_lock_t lock; + unsigned long generation; unsigned int position; - int generation; };
/* @@ -1633,14 +1629,14 @@ u64 get_random_u64(void) unsigned long flags; struct batched_entropy *batch; static void *previous; - int next_gen; + unsigned long next_gen;
warn_unseeded_randomness(&previous);
local_lock_irqsave(&batched_entropy_u64.lock, flags); batch = raw_cpu_ptr(&batched_entropy_u64);
- next_gen = atomic_read(&batch_generation); + next_gen = READ_ONCE(base_crng.generation); if (batch->position >= ARRAY_SIZE(batch->entropy_u64) || next_gen != batch->generation) { _get_random_bytes(batch->entropy_u64, sizeof(batch->entropy_u64)); @@ -1667,14 +1663,14 @@ u32 get_random_u32(void) unsigned long flags; struct batched_entropy *batch; static void *previous; - int next_gen; + unsigned long next_gen;
warn_unseeded_randomness(&previous);
local_lock_irqsave(&batched_entropy_u32.lock, flags); batch = raw_cpu_ptr(&batched_entropy_u32);
- next_gen = atomic_read(&batch_generation); + next_gen = READ_ONCE(base_crng.generation); if (batch->position >= ARRAY_SIZE(batch->entropy_u32) || next_gen != batch->generation) { _get_random_bytes(batch->entropy_u32, sizeof(batch->entropy_u32)); @@ -1690,15 +1686,6 @@ u32 get_random_u32(void) } EXPORT_SYMBOL(get_random_u32);
-/* It's important to invalidate all potential batched entropy that might - * be stored before the crng is initialized, which we can do lazily by - * bumping the generation counter. - */ -static void invalidate_batched_entropy(void) -{ - atomic_inc(&batch_generation); -} - /** * randomize_page - Generate a random, page aligned address * @start: The smallest acceptable address the caller will take.