sched/topology: Check variable group before dereferencing it

The 'group' variable in sched_domain_debug_one() is not checked
when firstly used in cpumask_test_cpu(cpu, sched_group_span(group)),
but it might be NULL (it is checked later in the following while loop)
and may cause NULL pointer dereference.

We need to check it before using to avoid NULL dereference.

Signed-off-by: Yi Wang <wang.yi59@zte.com.cn>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Jiang Biao <jiang.biao2@zte.com.cn>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: zhong.weidong@zte.com.cn
Link: http://lkml.kernel.org/r/1532319547-33335-1-git-send-email-wang.yi59@zte.com.cn
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 05a831427bc741e8d6290a6189bedbfda2457ded..56a0fed30c0a8786a47c600e90c4016140b1fb58 100644 (file)
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -47,7 +47,7 @@ static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
        if (!cpumask_test_cpu(cpu, sched_domain_span(sd))) {
                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);
        }