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@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 11 insertions, 5 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 0158d3bff7e5..4e2627a8d226 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);
 }