[PATCH 11/11] Entropy fixes - independent pool for /dev/urandom

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Stop /dev/urandom readers from starving /dev/random for entropy by
creating a separate pool and not reseeding if doing so would prevent
/dev/random from reseeding.

diff -ur a/drivers/char/random.c b/drivers/char/random.c
--- a/drivers/char/random.c 2002-09-08 21:00:11.000000000 -0500
+++ b/drivers/char/random.c 2002-09-08 21:45:13.000000000 -0500
@@ -365,7 +365,7 @@
 /*
  * Static global variables
  */
-static struct entropy_store *input_pool, *blocking_pool;
+static struct entropy_store *input_pool, *blocking_pool, *nonblocking_pool;
 static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
 static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
 
@@ -601,6 +601,7 @@
 
         /* switch pools if current full */
         if (r->entropy_count >= r->poolinfo->POOLBITS) r = blocking_pool;
+ if (r->entropy_count >= r->poolinfo->POOLBITS) r = nonblocking_pool;
 
         /* Don't allow more credit BITS > pool WORDS */
         if(credit > batch_max) credit=batch_max;
@@ -1004,16 +1005,17 @@
  */
 void get_random_bytes(void *buf, int nbytes)
 {
- if (!blocking_pool)
+ if (!nonblocking_pool)
         {
                 printk(KERN_NOTICE "get_random_bytes called before "
                                    "random driver initialization\n");
                 return;
         }
 
- reseed_pool(blocking_pool,
- random_read_wakeup_thresh, random_read_wakeup_thresh);
- extract_entropy(blocking_pool, (char *) buf, nbytes, 0);
+ /* Leave enough for blocking pool to reseed itself */
+ reseed_pool(nonblocking_pool,
+ random_read_wakeup_thresh*2, random_read_wakeup_thresh);
+ extract_entropy(nonblocking_pool, (char *) buf, nbytes, 0);
 }
 
 /*********************************************************************
@@ -1055,8 +1057,9 @@
 {
         input_pool = create_entropy_store(512, "input");
         blocking_pool = create_entropy_store(128, "blocking");
+ nonblocking_pool = create_entropy_store(128, "nonblocking");
 
- if(!(input_pool && blocking_pool)) return;
+ if(!(input_pool && blocking_pool && nonblocking_pool)) return;
         if(batch_entropy_init(256)) return;
 
         init_std_data(input_pool);
@@ -1134,10 +1137,10 @@
 urandom_read(struct file * file, char * buf,
                       size_t nbytes, loff_t *ppos)
 {
- reseed_pool(blocking_pool,
- random_read_wakeup_thresh, random_read_wakeup_thresh);
+ reseed_pool(nonblocking_pool,
+ random_read_wakeup_thresh*2, random_read_wakeup_thresh);
 
- return extract_entropy(blocking_pool, buf, nbytes,
+ return extract_entropy(nonblocking_pool, buf, nbytes,
                                EXTRACT_ENTROPY_USER);
 }
 

-- 
 "Love the dolphins," she advised him. "Write by W.A.S.T.E.." 
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