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

[Kamal Mostafa]

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-3.8.y-queue branch of the 3.8.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-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.15.

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

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 51c575a14f672b33506776f391078ea47b19a66e 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>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 mm/rmap.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/rmap.c b/mm/rmap.c
index 92b4529..c208837 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