Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751600AbWHSAfT (ORCPT ); Fri, 18 Aug 2006 20:35:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751604AbWHSAfS (ORCPT ); Fri, 18 Aug 2006 20:35:18 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:43950 "EHLO e33.co.us.ibm.com") by vger.kernel.org with ESMTP id S1751600AbWHSAfR (ORCPT ); Fri, 18 Aug 2006 20:35:17 -0400 Subject: [PATCH] rcu: Fix sign bug making rcu_random always return the same sequence From: Josh Triplett To: linux-kernel@vger.kernel.org Cc: Andrew Morton , Paul McKenney , Dipkanar Sarma Content-Type: text/plain Date: Fri, 18 Aug 2006 17:35:17 -0700 Message-Id: <1155947717.5337.9.camel@josh-work.beaverton.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.6.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1606 Lines: 46 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 --- 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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/