[tip:sched/core] sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT_PRIO in cpupri check

["tip-bot for Steven Rostedt (Red Hat)" <tipbot@zytor.com>]

Commit-ID:  6227cb00cc120f9a43ce8313bb0475ddabcb7d01
Gitweb:     http://git.kernel.org/tip/6227cb00cc120f9a43ce8313bb0475ddabcb7d01
Author:     Steven Rostedt (Red Hat) <rostedt@goodmis.org>
AuthorDate: Sun, 13 Apr 2014 09:34:53 -0400
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 7 May 2014 11:51:33 +0200

sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT_PRIO in cpupri check

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>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1397015410.5212.13.camel@marge.simpson.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/cpupri.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/sched/cpupri.c b/kernel/sched/cpupri.c
index 8b836b3..3031bac 100644
--- a/kernel/sched/cpupri.c
+++ b/kernel/sched/cpupri.c
@@ -70,8 +70,7 @@ 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];