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Subject[PATCH 2/4] random: make add_timer_randomness() fill the nonblocking pool first
Date
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>
---
drivers/char/random.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 51153fe..b578c03 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();
}
--
1.7.12.rc0.22.gcdd159b


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