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authorTheodore Ts'o <tytso@mit.edu>2013-11-03 16:40:53 -0500
committerTheodore Ts'o <tytso@mit.edu>2013-11-03 18:20:05 -0500
commit644008df899ec252e78db28c1b6d6b86779aada8 (patch)
tree4d33e8e3bb0d9c487bc337e2b9c44387bc847a71 /drivers/char
parentae9ecd92ddabc250817baa7eb401df3cfbd4c2da (diff)
downloadlinux-linaro-stable-644008df899ec252e78db28c1b6d6b86779aada8.tar.gz
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>
Diffstat (limited to 'drivers/char')
-rw-r--r--drivers/char/random.c8
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