1 files changed, 14 insertions, 5 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index caef35a46890..d4ddeba56682 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -128,6 +128,7 @@
  *      void add_input_randomness(unsigned int type, unsigned int code,
  *                                unsigned int value);
  *      void add_interrupt_randomness(int irq);
+ *      void add_disk_randomness(struct gendisk *disk);
  *
  * add_input_randomness() uses the input layer interrupt timing, as well as
  * the event type information from the hardware.
@@ -136,9 +137,15 @@
  * inputs to the entropy pool.  Note that not all interrupts are good
  * sources of randomness!  For example, the timer interrupts is not a
  * good choice, because the periodicity of the interrupts is too
- * regular, and hence predictable to an attacker.  Disk interrupts are
- * a better measure, since the timing of the disk interrupts are more
- * unpredictable.
+ * regular, and hence predictable to an attacker.  Network Interface
+ * Controller interrupts are a better measure, since the timing of the
+ * NIC interrupts are more unpredictable.
+ *
+ * add_disk_randomness() uses what amounts to the seek time of block
+ * layer request events, on a per-disk_devt basis, as input to the
+ * entropy pool. Note that high-speed solid state drives with very low
+ * seek times do not make for good sources of entropy, as their seek
+ * times are usually fairly consistent.
  *
  * All of these routines try to estimate how many bits of randomness a
  * particular randomness source.  They do this by keeping track of the
@@ -626,7 +633,7 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
         preempt_disable();
         /* if over the trickle threshold, use only 1 in 4096 samples */
         if (input_pool.entropy_count > trickle_thresh &&
-            (__get_cpu_var(trickle_count)++ & 0xfff))
+            ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
                 goto out;
 
         sample.jiffies = jiffies;
@@ -725,7 +732,7 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf,
                                size_t nbytes, int min, int rsvd);
 
 /*
- * This utility inline function is responsible for transfering entropy
+ * This utility inline function is responsible for transferring entropy
  * from the primary pool to the secondary extraction pool. We make
  * sure we pull enough for a 'catastrophic reseed'.
  */
@@ -1165,6 +1172,7 @@ const struct file_operations random_fops = {
         .poll  = random_poll,
         .unlocked_ioctl = random_ioctl,
         .fasync = random_fasync,
+        .llseek = noop_llseek,
 };
 
 const struct file_operations urandom_fops = {
@@ -1172,6 +1180,7 @@ const struct file_operations urandom_fops = {
         .write = random_write,
         .unlocked_ioctl = random_ioctl,
         .fasync = random_fasync,
+        .llseek = noop_llseek,
 };
 
 /***************************************************************