Messages in this thread | | | Date | Fri, 18 Aug 2006 17:50:46 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] rcu: Fix sign bug making rcu_random always return the same sequence |
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On Fri, Aug 18, 2006 at 05:35:17PM -0700, Josh Triplett wrote: > 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.
Acked-by: Paul E. McKenney <paulmck@us.ibm.com> > Signed-off-by: Josh Triplett <josh@freedesktop.org> > --- > 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/
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