commit: 08fa29d916c6e271ad13978cd993e7238c68db97
From: Sasha Levin <[email protected]>
Date: Tue, 29 May 2012 15:06:15 -0700
Subject: mm: fix NULL ptr deref when walking hugepages
A missing validation of the value returned by find_vma() could cause a
NULL ptr dereference when walking the pagetable.
This is triggerable from usermode by a simple user by trying to read a
page info out of /proc/pid/pagemap which doesn't exist.
Introduced by commit 025c5b2451e4 ("thp: optimize away unnecessary page
table locking").
Signed-off-by: Sasha Levin <[email protected]>
Reviewed-by: Naoya Horiguchi <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: <[email protected]> [3.4.x]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
---
fs/proc/task_mmu.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 1030a71..7faaf2a 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -784,7 +784,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long
addr, unsigned long end,
/* find the first VMA at or above 'addr' */
vma = find_vma(walk->mm, addr);
- if (pmd_trans_huge_lock(pmd, vma) == 1) {
+ if (vma && pmd_trans_huge_lock(pmd, vma) == 1) {
for (; addr != end; addr += PAGE_SIZE) {
unsigned long offset;
--
1.7.3.4
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