[3.5.y.z extended stable] Patch "mm/hugetlb: check for pte NULL pointer in __page_check_address()" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 9c5f5ddfcbce49137838bfe925a740b1dc8cabb6 Mon Sep 17 00:00:00 2001
From: Jianguo Wu <wujianguo at huawei.com>
Date: Wed, 18 Dec 2013 17:08:59 -0800
Subject: mm/hugetlb: check for pte NULL pointer in __page_check_address()

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 at huawei.com>
Cc: Naoya Horiguchi <n-horiguchi at ah.jp.nec.com>
Cc: Mel Gorman <mgorman at suse.de>
Cc: qiuxishi <qiuxishi at huawei.com>
Cc: Hanjun Guo <guohanjun at huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov at linux.intel.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 mm/rmap.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/rmap.c b/mm/rmap.c
index aa95e59..2b03b31 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -623,7 +623,11 @@ 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