| From 08fa29d916c6e271ad13978cd993e7238c68db97 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <levinsasha928@gmail.com> |
| Date: Tue, 29 May 2012 15:06:15 -0700 |
| Subject: mm: fix NULL ptr deref when walking hugepages |
| |
| From: Sasha Levin <levinsasha928@gmail.com> |
| |
| commit 08fa29d916c6e271ad13978cd993e7238c68db97 upstream. |
| |
| 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 <levinsasha928@gmail.com> |
| Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> |
| Cc: David Rientjes <rientjes@google.com> |
| Cc: Andi Kleen <andi@firstfloor.org> |
| Cc: Andrea Arcangeli <aarcange@redhat.com> |
| Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> |
| Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| fs/proc/task_mmu.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/fs/proc/task_mmu.c |
| +++ b/fs/proc/task_mmu.c |
| @@ -784,7 +784,7 @@ static int pagemap_pte_range(pmd_t *pmd, |
| |
| /* 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; |
| |
