From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751568AbaFRNdf (ORCPT ); Wed, 18 Jun 2014 09:33:35 -0400 Received: from mx2.parallels.com ([199.115.105.18]:42597 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750862AbaFRNde (ORCPT ); Wed, 18 Jun 2014 09:33:34 -0400 From: Vladimir Davydov To: CC: , , , , Subject: [PATCH] fork: dup_mm: init vm stat counters under mmap_sem Date: Wed, 18 Jun 2014 17:33:11 +0400 Message-ID: <1403098391-24546-1-git-send-email-vdavydov@parallels.com> X-Mailer: git-send-email 1.7.10.4 MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If a forking process has a thread calling (un)mmap (silly but still), the child process may have some of its mm's vm stats (total_vm and friends) screwed up, because currently they are copied from oldmm w/o holding any locks (see dup_mm). This patch moves the stats initialization to dup_mmap to be called under oldmm->mmap_sem, which eliminates any possibility of race. Also, mm->pinned_vm is not reset on fork. Let's fix it. Signed-off-by: Vladimir Davydov --- kernel/fork.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/fork.c b/kernel/fork.c index d2799d1fc952..eaacc75da4f7 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -365,7 +365,12 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) */ down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); + mm->total_vm = oldmm->total_vm; mm->locked_vm = 0; + mm->pinned_vm = 0; + mm->shared_vm = oldmm->shared_vm; + mm->exec_vm = oldmm->exec_vm; + mm->stack_vm = oldmm->stack_vm; mm->mmap = NULL; mm->vmacache_seqnum = 0; mm->map_count = 0; -- 1.7.10.4