random: make add_timer_randomness() fill the nonblocking pool first

Change add_timer_randomness() so that it directs incoming entropy to
the nonblocking pool first if it hasn't been fully initialized yet.
This matches the strategy we use in add_interrupt_randomness(), which
allows us to push the randomness where we need it the most during when
the system is first booting up, so that get_random_bytes() and
/dev/urandom become safe to use as soon as possible.

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

1 files changed, 4 insertions, 3 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index f126bd2f69fe..62923138e77a 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -761,6 +761,7 @@ static struct timer_rand_state input_timer_state;
  */
 static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
 {
+        struct entropy_store    *r;
         struct {
                 long jiffies;
                 unsigned cycles;
@@ -773,7 +774,8 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
         sample.jiffies = jiffies;
         sample.cycles = random_get_entropy();
         sample.num = num;
-        mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL);
+        r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
+        mix_pool_bytes(r, &sample, sizeof(sample), NULL);
 
         /*
          * Calculate number of bits of randomness we probably added.
@@ -807,8 +809,7 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
                  * Round down by 1 bit on general principles,
                  * and limit entropy entimate to 12 bits.
                  */
-                credit_entropy_bits(&input_pool,
-                                    min_t(int, fls(delta>>1), 11));
+                credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
         }
         preempt_enable();
 }