[PATCH] rcu: Fix sign bug making rcu_random always return the same sequence

rcu_random uses a counter rrs_count to occasionally mix data from
get_random_bytes into the state of its pseudorandom generator. However, the
rrs_counter gets declared as an unsigned long, and rcu_random checks for
--rrs_count < 0, so this code will never mix any real random data into the
state, and will thus always return the same sequence of random numbers.

Also, change the return value of rcu_random from long to unsigned long, to
avoid potential issues caused by the use of the % operator, which can return
negative values for negative left operands.

Signed-off-by: Josh Triplett <josh@xxxxxxxxxxxxxxx>
---
kernel/rcutorture.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 8b09c95..ef6a124 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -146,7 +146,7 @@ rcu_torture_free(struct rcu_torture *p)

struct rcu_random_state {
unsigned long rrs_state;
- unsigned long rrs_count;
+ long rrs_count;
};

#define RCU_RANDOM_MULT 39916801 /* prime */
@@ -159,7 +159,7 @@ #define DEFINE_RCU_RANDOM(name) struct r
* Crude but fast random-number generator. Uses a linear congruential
* generator, with occasional help from get_random_bytes().
*/
-static long
+static unsigned long
rcu_random(struct rcu_random_state *rrsp)
{
long refresh;
--
1.4.1.1


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