From: Josh Triplett Date: Wed, 4 Oct 2006 09:17:12 +0000 (-0700) Subject: [PATCH] rcu: Fix sign bug making rcu_random always return the same sequence X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=75cfef32f26d03f5d0a0833572d52f94ad858a36;p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.git [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 Acked-by: Paul E. McKenney Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c index 42e7f01e8003..43d6d4f9ef09 100644 --- a/kernel/rcutorture.c +++ b/kernel/rcutorture.c @@ -147,7 +147,7 @@ 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 */ @@ -160,7 +160,7 @@ struct rcu_random_state { * 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;