From a2198407845fa9d85b590eafafacf3b6a82d3528 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 19 Nov 2013 16:41:49 +0100
Subject: sched: Avoid NULL dereference on sd_busy

commit 42eb088ed246a5a817bb45a8b32fe234cf1c0f8b upstream.

Commit 37dc6b50cee9 ("sched: Remove unnecessary iteration over sched
domains to update nr_busy_cpus") forgot to clear 'sd_busy' under some
conditions leading to a possible NULL deref in set_cpu_sd_state_idle().

Reported-by: Anton Blanchard <anton@samba.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131118113701.GF3866@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6135b7c..bc2f26d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5132,8 +5132,9 @@ static void update_top_cache_domain(int cpu)
 	if (sd) {
 		id = cpumask_first(sched_domain_span(sd));
 		size = cpumask_weight(sched_domain_span(sd));
-		rcu_assign_pointer(per_cpu(sd_busy, cpu), sd->parent);
+		sd = sd->parent; /* sd_busy */
 	}
+	rcu_assign_pointer(per_cpu(sd_busy, cpu), sd);
 
 	rcu_assign_pointer(per_cpu(sd_llc, cpu), sd);
 	per_cpu(sd_llc_size, cpu) = size;
-- 
cgit v0.10.2