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| author | Theodore Ts'o <tytso@mit.edu> | 2013-11-03 22:40:53 +0100 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2013-11-04 00:20:05 +0100 |
| commit | 644008df899ec252e78db28c1b6d6b86779aada8 (patch) | |
| tree | 4d33e8e3bb0d9c487bc337e2b9c44387bc847a71 | |
| parent | random: don't zap entropy count in rand_initialize() (diff) | |
| download | linux-644008df899ec252e78db28c1b6d6b86779aada8.tar.xz linux-644008df899ec252e78db28c1b6d6b86779aada8.zip | |
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" <tytso@mit.edu>
| -rw-r--r-- | drivers/char/random.c | 8 |
1 files changed, 6 insertions, 2 deletions
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 |