memcg: null dereference on allocation failure

The original code had a null dereference if alloc_percpu() failed. This
was introduced in commit 711d3d2c9bc3 ("memcg: cpu hotplug aware percpu
count updates")

Signed-off-by: Dan Carpenter <[e-mail]>
Reviewed-by: Balbir Singh <[e-mail]>
Acked-by: KAMEZAWA Hiroyuki <[e-mail]>
Acked-by: Daisuke Nishimura <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

mm/memcontrol.c

···
 
 	memset(mem, 0, size);
 	mem->stat = alloc_percpu(struct mem_cgroup_stat_cpu);
-	if (!mem->stat) {
-		if (size < PAGE_SIZE)
-			kfree(mem);
-		else
-			vfree(mem);
-		mem = NULL;
-	}
+	if (!mem->stat)
+		goto out_free;
 	spin_lock_init(&mem->pcp_counter_lock);
 	return mem;
+
+out_free:
+	if (size < PAGE_SIZE)
+		kfree(mem);
+	else
+		vfree(mem);
+	return NULL;
 }
 
 /*