mm/hugetlb: check for pte NULL pointer in __page_check_address()

Jianguo Wu · torvalds · commit 98398c32f668 · 2013-12-18T19:04:52.000-08:00
In __page_check_address(), if address's pud is not present,
huge_pte_offset() will return NULL, we should check the return value.

Signed-off-by: Jianguo Wu &lt;wujianguo@huawei.com&gt;
Cc: Naoya Horiguchi &lt;n-horiguchi@ah.jp.nec.com&gt;
Cc: Mel Gorman &lt;mgorman@suse.de&gt;
Cc: qiuxishi &lt;qiuxishi@huawei.com&gt;
Cc: Hanjun Guo &lt;guohanjun@huawei.com&gt;
Acked-by: Kirill A. Shutemov &lt;kirill.shutemov@linux.intel.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
diff --git a/mm/rmap.c b/mm/rmap.c
@@ -600,7 +600,11 @@ pte_t *__page_check_address(struct page *page, struct mm_struct *mm,
 	spinlock_t *ptl;
 
 	if (unlikely(PageHuge(page))) {
+		/* when pud is not present, pte will be NULL */
 		pte = huge_pte_offset(mm, address);
+		if (!pte)
+			return NULL;
+
 		ptl = huge_pte_lockptr(page_hstate(page), mm, pte);
 		goto check;
 	}
