mm: Check page status in page_reliable()

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4SK3S
CVE: NA

--------------------------------

Check whether page is NULL or not in page_reliable(). Return false if page
is NULL.
Signed-off-by: NMa Wupeng <mawupeng1@huawei.com>
Reviewed-by: Kefeng Wang<wangkefeng.wang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

include/linux/mem_reliable.h

@@ -107,7 +107,7 @@ static inline void shmem_reliable_page_counter(struct page *page, int nr_page)
 
 static inline void mem_reliable_buddy_counter(struct page *page, int nr_page)
 {
-	if (page && page_reliable(page))
+	if (page_reliable(page))
 		this_cpu_add(nr_reliable_buddy_pages, nr_page);
 }
 

mm/mem_reliable.c

@@ -53,12 +53,15 @@ void add_reliable_mem_size(long sz)
 
 bool page_reliable(struct page *page)
 {
-	return mem_reliable_is_enabled() && page_zonenum(page) < ZONE_MOVABLE;
+	if (!mem_reliable_is_enabled() || !page)
+		return false;
+
+	return page_zonenum(page) < ZONE_MOVABLE;
 }
 
 static bool reliable_and_lru_check(enum lru_list lru, struct page *page)
 {
-	if (!page || !page_reliable(page))
+	if (!page_reliable(page))
 		return false;
 
 	if (lru != LRU_ACTIVE_FILE && lru != LRU_INACTIVE_FILE)