From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Date: Thu, 22 May 2014 00:42:43 +0000 (+1000)
Subject: mm/pagewalk.c: move pte null check
X-Git-Tag: next-20140530~2^2~385
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=9e9df4dda900317c0a431d096d1dface033ebbd9;p=karo-tx-linux.git

mm/pagewalk.c: move pte null check

huge_pte_offset() can return NULL, so we need check it before trying to
take page table lock to avoid a crash.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index a834f4deb527..b2a075ffb96e 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -193,12 +193,14 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
 	do {
 		next = hugetlb_entry_end(h, addr, end);
 		pte = huge_pte_offset(walk->mm, addr & hmask);
+		if (!pte)
+			continue;
 		ptl = huge_pte_lock(h, mm, pte);
 		/*
 		 * Callers should have their own way to handle swap entries
 		 * in walk->hugetlb_entry().
 		 */
-		if (pte && walk->hugetlb_entry)
+		if (walk->hugetlb_entry)
 			err = walk->hugetlb_entry(pte, addr, next, walk);
 		spin_unlock(ptl);
 		if (err)