linux-kernel - [PATCH 3.2 61/92] sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT

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Message-ID: <lsq.1402104389.591367832@decadent.org.uk>
Date:	Sat, 07 Jun 2014 02:26:29 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Ingo Molnar" <mingo@...nel.org>,
	"Mike Galbraith" <umgwanakikbuti@...il.com>,
	"Peter Zijlstra" <peterz@...radead.org>,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
Subject: [PATCH 3.2 61/92] sched: Use CPUPRI_NR_PRIORITIES instead of
 MAX_RT_PRIO in cpupri check

3.2.60-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>

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@...il.com>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/1397015410.5212.13.camel@marge.simpson.net
Signed-off-by: Ingo Molnar <mingo@...nel.org>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/sched/cpupri.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/kernel/sched_cpupri.c
+++ b/kernel/sched_cpupri.c
@@ -68,8 +68,7 @@ int cpupri_find(struct cpupri *cp, struc
 	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];

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