diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 962b14d..46ffab8 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1397,13 +1397,16 @@ static inline unsigned long *section_to_usemap(struct mem_section *ms)
 
 static inline struct mem_section *__nr_to_section(unsigned long nr)
 {
+	unsigned long root = SECTION_NR_TO_ROOT(nr);
+
+	if (unlikely(root >= NR_SECTION_ROOTS))
+		return NULL;
+
 #ifdef CONFIG_SPARSEMEM_EXTREME
-	if (!mem_section)
+	if (!mem_section || !mem_section[root])
 		return NULL;
 #endif
-	if (!mem_section[SECTION_NR_TO_ROOT(nr)])
-		return NULL;
-	return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
+	return &mem_section[root][nr & SECTION_ROOT_MASK];
 }
 extern size_t mem_section_usage_size(void);