mm: fix NULL ptr dereference in __count_immobile_pages

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / mm / page_alloc.c

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0027d8f4a1bb8b1423f42e4d52cb3547debc315f..21c272d517bc45a787de56bc7218d7581a3603d2 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5414,6 +5414,17 @@ __count_immobile_pages(struct zone *zone, struct page *page, int count)
 bool is_pageblock_removable_nolock(struct page *page)
 {
        struct zone *zone = page_zone(page);
+       unsigned long pfn = page_to_pfn(page);
+
+       /*
+        * We have to be careful here because we are iterating over memory
+        * sections which are not zone aware so we might end up outside of
+        * the zone but still within the section.
+        */
+       if (!zone || zone->zone_start_pfn > pfn ||
+                       zone->zone_start_pfn + zone->spanned_pages <= pfn)
+               return false;
+
        return __count_immobile_pages(zone, page, 0);
 }