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);
}
--
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