From 644008df899ec252e78db28c1b6d6b86779aada8 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Sun, 3 Nov 2013 16:40:53 -0500 Subject: random: initialize the last_time field in struct timer_rand_state Since we initialize jiffies to wrap five minutes before boot (see INITIAL_JIFFIES defined in include/linux/jiffies.h) it's important to make sure the last_time field is initialized to INITIAL_JIFFIES. Otherwise, the entropy estimator will overestimate the amount of entropy resulting from the first call to add_timer_randomness(), generally by about 8 bits. Signed-off-by: "Theodore Ts'o" --- drivers/char/random.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'drivers/char') diff --git a/drivers/char/random.c b/drivers/char/random.c index a38d97a21455..0894d86253fd 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -724,6 +724,8 @@ struct timer_rand_state { unsigned dont_count_entropy:1; }; +#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, }; + /* * Add device- or boot-specific data to the input and nonblocking * pools to help initialize them to unique values. @@ -750,7 +752,7 @@ void add_device_randomness(const void *buf, unsigned int size) } EXPORT_SYMBOL(add_device_randomness); -static struct timer_rand_state input_timer_state; +static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE; /* * This function adds entropy to the entropy "pool" by using timing @@ -1267,8 +1269,10 @@ void rand_initialize_disk(struct gendisk *disk) * source. */ state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL); - if (state) + if (state) { + state->last_time = INITIAL_JIFFIES; disk->random = state; + } } #endif -- cgit v1.2.3-59-g8ed1b