From 4af712e8df998475736f3e2727701bd31e3751a9 Mon Sep 17 00:00:00 2001 From: Hannes Frederic Sowa Date: Mon, 11 Nov 2013 12:20:34 +0100 Subject: [PATCH] random32: add prandom_reseed_late() and call when nonblocking pool becomes initialized The Tausworthe PRNG is initialized at late_initcall time. At that time the entropy pool serving get_random_bytes is not filled sufficiently. This patch adds an additional reseeding step as soon as the nonblocking pool gets marked as initialized. On some machines it might be possible that late_initcall gets called after the pool has been initialized. In this situation we won't reseed again. (A call to prandom_seed_late blocks later invocations of early reseed attempts.) Joint work with Daniel Borkmann. Cc: Eric Dumazet Cc: Theodore Ts'o Signed-off-by: Hannes Frederic Sowa Signed-off-by: Daniel Borkmann Acked-by: "Theodore Ts'o" Signed-off-by: David S. Miller --- drivers/char/random.c | 5 ++++- include/linux/random.h | 1 + lib/random32.c | 23 ++++++++++++++++++++++- 3 files changed, 27 insertions(+), 2 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 7a744d39175..4fe5609eeb7 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -603,8 +603,11 @@ retry: if (!r->initialized && nbits > 0) { r->entropy_total += nbits; - if (r->entropy_total > 128) + if (r->entropy_total > 128) { r->initialized = 1; + if (r == &nonblocking_pool) + prandom_reseed_late(); + } } trace_credit_entropy_bits(r->name, nbits, entropy_count, diff --git a/include/linux/random.h b/include/linux/random.h index bf9085e89fb..5117ae348fe 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -29,6 +29,7 @@ unsigned long randomize_range(unsigned long start, unsigned long end, unsigned l u32 prandom_u32(void); void prandom_bytes(void *buf, int nbytes); void prandom_seed(u32 seed); +void prandom_reseed_late(void); u32 prandom_u32_state(struct rnd_state *); void prandom_bytes_state(struct rnd_state *state, void *buf, int nbytes); diff --git a/lib/random32.c b/lib/random32.c index 12215df701e..9f2f2fb03df 100644 --- a/lib/random32.c +++ b/lib/random32.c @@ -200,9 +200,18 @@ static void prandom_start_seed_timer(void) * Generate better values after random number generator * is fully initialized. */ -static int __init prandom_reseed(void) +static void __prandom_reseed(bool late) { int i; + unsigned long flags; + static bool latch = false; + static DEFINE_SPINLOCK(lock); + + /* only allow initial seeding (late == false) once */ + spin_lock_irqsave(&lock, flags); + if (latch && !late) + goto out; + latch = true; for_each_possible_cpu(i) { struct rnd_state *state = &per_cpu(net_rand_state,i); @@ -216,6 +225,18 @@ static int __init prandom_reseed(void) /* mix it in */ prandom_u32_state(state); } +out: + spin_unlock_irqrestore(&lock, flags); +} + +void prandom_reseed_late(void) +{ + __prandom_reseed(true); +} + +static int __init prandom_reseed(void) +{ + __prandom_reseed(false); prandom_start_seed_timer(); return 0; } -- 2.43.2