linux-kernel - [PATCH 3.11 014/208] mm/hugetlb: check for pte NULL pointer in __page_check

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Message-Id: <1389628849-1614-15-git-send-email-luis.henriques@canonical.com>
Date:	Mon, 13 Jan 2014 15:57:35 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Jianguo Wu <wujianguo@...wei.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Mel Gorman <mgorman@...e.de>, qiuxishi <qiuxishi@...wei.com>,
	Hanjun Guo <guohanjun@...wei.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.11 014/208] mm/hugetlb: check for pte NULL pointer in __page_check_address()

3.11.10.3 -stable review patch.  If anyone has any objections, please let me know.

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

From: Jianguo Wu <wujianguo@...wei.com>

commit 98398c32f6687ee1e1f3ae084effb4b75adb0747 upstream.

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 <wujianguo@...wei.com>
Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc: Mel Gorman <mgorman@...e.de>
Cc: qiuxishi <qiuxishi@...wei.com>
Cc: Hanjun Guo <guohanjun@...wei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
[ luis: backported to 3.11: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 mm/rmap.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/rmap.c b/mm/rmap.c
index b2e29ac..75f4c82 100644
--- 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 = &mm->page_table_lock;
 		goto check;
 	}
-- 
1.8.3.2

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