linux-kernel - [PATCH 1/7] random: initialize the non-blocking pool via add_hwgenerator

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Date:	Mon, 13 Jun 2016 11:48:33 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Linux Kernel Developers List <linux-kernel@...r.kernel.org>
Cc:	linux-crypto@...r.kernel.org, smueller@...onox.de,
	herbert@...dor.apana.org.au, andi@...stfloor.org,
	sandyinchina@...il.com, jsd@...n.com, hpa@...or.com,
	Theodore Ts'o <tytso@....edu>, stable@...nel.org
Subject: [PATCH 1/7] random: initialize the non-blocking pool via add_hwgenerator_randomness()

If we have a hardware RNG and are using the in-kernel rngd, we should
use this to initialize the non-blocking pool so that getrandom(2)
doesn't block unnecessarily.

Cc: stable@...nel.org
Signed-off-by: Theodore Ts'o <tytso@....edu>
---
 drivers/char/random.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 0158d3b..4e2627a 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1849,12 +1849,18 @@ void add_hwgenerator_randomness(const char *buffer, size_t count,
 {
 	struct entropy_store *poolp = &input_pool;
 
-	/* Suspend writing if we're above the trickle threshold.
-	 * We'll be woken up again once below random_write_wakeup_thresh,
-	 * or when the calling thread is about to terminate.
-	 */
-	wait_event_interruptible(random_write_wait, kthread_should_stop() ||
+	if (unlikely(nonblocking_pool.initialized == 0))
+		poolp = &nonblocking_pool;
+	else {
+		/* Suspend writing if we're above the trickle
+		 * threshold.  We'll be woken up again once below
+		 * random_write_wakeup_thresh, or when the calling
+		 * thread is about to terminate.
+		 */
+		wait_event_interruptible(random_write_wait,
+					 kthread_should_stop() ||
 			ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
+	}
 	mix_pool_bytes(poolp, buffer, count);
 	credit_entropy_bits(poolp, entropy);
 }
-- 
2.5.0