From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 19 Nov 2013 15:41:49 +0000 (+0100)
Subject: sched: Avoid NULL dereference on sd_busy
X-Git-Tag: next-20131128~20^2~5^2~2
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=42eb088e;p=karo-tx-linux.git

sched: Avoid NULL dereference on sd_busy

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>
---

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c1808606ee5f..a1591ca7eb5a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4910,8 +4910,9 @@ 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;