From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx178.postini.com [74.125.245.178]) by kanga.kvack.org (Postfix) with SMTP id 4BD936B00E7 for ; Wed, 23 May 2012 03:19:47 -0400 (EDT) Received: by bkcjm19 with SMTP id jm19so8171596bkc.14 for ; Wed, 23 May 2012 00:19:45 -0700 (PDT) From: Sasha Levin Subject: [PATCH] mm: fix NULL ptr deref when walking hugepages Date: Wed, 23 May 2012 09:20:43 +0200 Message-Id: <1337757643-18302-1-git-send-email-levinsasha928@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org, n-horiguchi@ah.jp.nec.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Sasha Levin A missing vlidation 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 025c5b24 ("thp: optimize away unnecessary page table locking"). Signed-off-by: Sasha Levin --- 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 3e564f0..885830b 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -820,7 +820,7 @@ 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; -- 1.7.8.6 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org