[PATCH] sched/topology: check variable group before dereferenced

[Yi Wang]

The variable group in sched_domain_debug_one() is not checked
when firstly used in cpumask_test_cpu(cpu, sched_group_span(group)),
but it maybe NULL(checked later in the following while loop) and may
cause NULL pointer dereference without checking. We need to check it
before using to avoid NULL dereference.

Signed-off-by: Yi Wang <wang.y...@zte.com.cn>
Reviewed-by: Jiang Biao <jiang.bi...@zte.com.cn>
---
 kernel/sched/topology.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 5ac724b..c7cf87c 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -53,7 +53,7 @@ static int sched_domain_debug_one(struct sched_domain *sd, 
int cpu, int level,
                printk(KERN_ERR "ERROR: domain->span does not contain "
                                "CPU%d\n", cpu);
        }
-       if (!cpumask_test_cpu(cpu, sched_group_span(group))) {
+       if (group && !cpumask_test_cpu(cpu, sched_group_span(group))) {
                printk(KERN_ERR "ERROR: domain->groups does not contain"
                                " CPU%d\n", cpu);
        }
-- 
1.8.3.1