sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT_PRIO in cpupri check

commit 6227cb00cc120f9a43ce8313bb0475ddabcb7d01 upstream.

The check at the beginning of cpupri_find() makes sure that the task_pri
variable does not exceed the cp->pri_to_cpu array length. But that length
is CPUPRI_NR_PRIORITIES not MAX_RT_PRIO, where it will miss the last two
priorities in that array.

As task_pri is computed from convert_prio() which should never be bigger
than CPUPRI_NR_PRIORITIES, if the check should cause a panic if it is
hit.

Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1397015410.5212.13.camel@marge.simpson.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/kernel/sched_cpupri.c b/kernel/sched_cpupri.c
index a86cf9d..1f4afdd 100644 (file)
--- a/kernel/sched_cpupri.c
+++ b/kernel/sched_cpupri.c
@@ -68,8 +68,7 @@ int cpupri_find(struct cpupri *cp, struct task_struct *p,
        int                  idx      = 0;
        int                  task_pri = convert_prio(p->prio);
 
-       if (task_pri >= MAX_RT_PRIO)
-               return 0;
+       BUG_ON(task_pri >= CPUPRI_NR_PRIORITIES);
 
        for (idx = 0; idx < task_pri; idx++) {
                struct cpupri_vec *vec  = &cp->pri_to_cpu[idx];