[PATCH] Fix array overflow in CFQ

Andi Kleen
2010-10-19T09:11:42Z

From: Andi Kleen <ak@linux.intel.com>

gcc 4.5 complains when compiling a recent rc with

linux/block/cfq-iosched.c: In function ‘cfq_dispatch_requests’:
linux/block/cfq-iosched.c:2156:3: warning: array subscript is above array bounds

and it is right:

slice = group_slice * count /
max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));

busy_queues_avg can be indexed by this enum

enum wl_prio_t {
BE_WORKLOAD = 0,
RT_WORKLOAD = 1,
IDLE_WORKLOAD = 2,
};

in cfqd->serving_prio, but is only declared as

unsigned int busy_queues_avg[2];

which is clearly off by one. Fix this here.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
block/cfq-iosched.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 9eba291..76741da 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -185,7 +185,7 @@ struct cfq_group {
int nr_cfqq;

/* Per group busy queus average. Useful for workload slice calc. */
- unsigned int busy_queues_avg[2];
+ unsigned int busy_queues_avg[3];
/*
* rr lists of queues with requests, onle rr for each priority class.
* Counts are embedded in the cfq_rb_root
--
1.7.1