Messages in this thread Patch in this message | | | Subject | [PATCH] rcu: Fix sign bug making rcu_random always return the same sequence | From | Josh Triplett <> | Date | Fri, 18 Aug 2006 17:35:17 -0700 |
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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@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
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