From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: Message-Id: <20120607040337.339599558@linuxfoundation.org> Date: Thu, 07 Jun 2012 13:03:42 +0900 From: Greg KH To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Sasha Levin , Naoya Horiguchi , David Rientjes , Andi Kleen , Andrea Arcangeli , KOSAKI Motohiro , KAMEZAWA Hiroyuki Subject: [ 06/82] mm: fix NULL ptr deref when walking hugepages In-Reply-To: <20120607041406.GA13233@kroah.com> List-ID: 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sasha Levin 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 Reviewed-by: Naoya Horiguchi Cc: David Rientjes Cc: Andi Kleen Cc: Andrea Arcangeli Cc: KOSAKI Motohiro Cc: KAMEZAWA Hiroyuki Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- 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;