From: Jason A. Donenfeld Jason@zx2c4.com
[ Upstream commit 122733471384be8c23f019fbbd46bdf7be561dcd ]
Counterintuitively, mod_timer(..., jiffies + 1) will cause the timer to fire not in the next jiffy, but in two jiffies. The way to cause the timer to fire in the next jiffy is with mod_timer(..., jiffies). Doing so then lets us bump the upper bound back up again.
Fixes: 50ee7529ec45 ("random: try to actively add entropy rather than passively wait for it") Fixes: 829d680e82a9 ("random: cap jitter samples per bit to factor of HZ") Cc: Dominik Brodowski linux@dominikbrodowski.net Cc: Sebastian Andrzej Siewior bigeasy@linutronix.de Cc: Sultan Alsawaf sultan@kerneltoast.com Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/char/random.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c index 060f999dcffb..46d6100fa3a7 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1195,7 +1195,7 @@ static void __cold entropy_timer(struct timer_list *timer) */ static void __cold try_to_generate_entropy(void) { - enum { NUM_TRIAL_SAMPLES = 8192, MAX_SAMPLES_PER_BIT = HZ / 30 }; + enum { NUM_TRIAL_SAMPLES = 8192, MAX_SAMPLES_PER_BIT = HZ / 15 }; struct entropy_timer_state stack; unsigned int i, num_different = 0; unsigned long last = random_get_entropy(); @@ -1214,7 +1214,7 @@ static void __cold try_to_generate_entropy(void) timer_setup_on_stack(&stack.timer, entropy_timer, 0); while (!crng_ready() && !signal_pending(current)) { if (!timer_pending(&stack.timer)) - mod_timer(&stack.timer, jiffies + 1); + mod_timer(&stack.timer, jiffies); mix_pool_bytes(&stack.entropy, sizeof(stack.entropy)); schedule(); stack.entropy = random_get_entropy();