diff mbox series

random: do not use batches when !crng_ready()

Message ID 20220503121836.522258-1-Jason@zx2c4.com (mailing list archive)
State Not Applicable
Delegated to: Herbert Xu
Headers show
Series random: do not use batches when !crng_ready() | expand

Commit Message

Jason A. Donenfeld May 3, 2022, 12:18 p.m. UTC 
It's too hard to keep the batches synchronized, and pointless anyway,
since in !crng_ready(), we're updating the base_crng key really often,
where batching only hurts. So instead, if the crng isn't ready, just
call into get_random_bytes(). At this stage nothing is performance
critical anyhow.

Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 drivers/char/random.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

Comments

Dominik Brodowski May 13, 2022, 6:25 a.m. UTC | #1 
Am Tue, May 03, 2022 at 02:18:36PM +0200 schrieb Jason A. Donenfeld:
> It's too hard to keep the batches synchronized, and pointless anyway,
> since in !crng_ready(), we're updating the base_crng key really often,
> where batching only hurts. So instead, if the crng isn't ready, just
> call into get_random_bytes(). At this stage nothing is performance
> critical anyhow.
> 
> Cc: Theodore Ts'o <tytso@mit.edu>
> Cc: Dominik Brodowski <linux@dominikbrodowski.net>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

	Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>

Thanks,
	Dominik
diff mbox series

Patch

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 346c9b16a7f1..53b8237687ed 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -610,6 +610,11 @@  u64 get_random_u64(void)
 
 	warn_unseeded_randomness(&previous);
 
+	if  (!crng_ready()) {
+		_get_random_bytes(&ret, sizeof(ret));
+		return ret;
+	}
+
 	local_lock_irqsave(&batched_entropy_u64.lock, flags);
 	batch = raw_cpu_ptr(&batched_entropy_u64);
 
@@ -644,6 +649,11 @@  u32 get_random_u32(void)
 
 	warn_unseeded_randomness(&previous);
 
+	if  (!crng_ready()) {
+		_get_random_bytes(&ret, sizeof(ret));
+		return ret;
+	}
+
 	local_lock_irqsave(&batched_entropy_u32.lock, flags);
 	batch = raw_cpu_ptr(&batched_entropy_u32);
 
@@ -820,10 +830,8 @@  static void credit_entropy_bits(size_t nbits)
 
 	if (unlikely(crng_init == 0 && entropy_count >= POOL_FAST_INIT_BITS)) {
 		spin_lock_irqsave(&base_crng.lock, flags);
-		if (crng_init == 0) {
-			++base_crng.generation;
+		if (crng_init == 0)
 			crng_init = 1;
-		}
 		spin_unlock_irqrestore(&base_crng.lock, flags);
 	}
 
@@ -1029,7 +1037,6 @@  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_ready()) {
 		crng_init = 2;