From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965272AbbI2SbU (ORCPT ); Tue, 29 Sep 2015 14:31:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50930 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935489AbbI2SbG (ORCPT ); Tue, 29 Sep 2015 14:31:06 -0400 Date: Tue, 29 Sep 2015 20:27:56 +0200 From: Oleg Nesterov To: Andrew Morton Cc: Andrey Konovalov , Davidlohr Bueso , Hugh Dickins , "Kirill A. Shutemov" , Sasha Levin , Vlastimil Babka , linux-kernel@vger.kernel.org Subject: [PATCH 1/2] mm: fix the racy mm->locked_vm change in Message-ID: <20150929182756.GA21740@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150929182734.GA21719@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "mm->locked_vm += grow" and vm_stat_account() in acct_stack_growth() are not safe; multiple threads using the same ->mm can do this at the same time trying to expans different vma's under down_read(mmap_sem). This means that one of the "locked_vm += grow" changes can be lost and we can miss munlock_vma_pages_all() later. Move this code into the caller(s) under mm->page_table_lock. All other updates to ->locked_vm hold mmap_sem for writing. Signed-off-by: Oleg Nesterov --- mm/mmap.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 8393580..4efdc37 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2138,10 +2138,6 @@ static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, uns if (security_vm_enough_memory_mm(mm, grow)) return -ENOMEM; - /* Ok, everything looks good - let it rip */ - if (vma->vm_flags & VM_LOCKED) - mm->locked_vm += grow; - vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow); return 0; } @@ -2202,6 +2198,10 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address) * against concurrent vma expansions. */ spin_lock(&vma->vm_mm->page_table_lock); + if (vma->vm_flags & VM_LOCKED) + vma->vm_mm->locked_vm += grow; + vm_stat_account(vma->vm_mm, vma->vm_flags, + vma->vm_file, grow); anon_vma_interval_tree_pre_update_vma(vma); vma->vm_end = address; anon_vma_interval_tree_post_update_vma(vma); @@ -2273,6 +2273,10 @@ int expand_downwards(struct vm_area_struct *vma, * against concurrent vma expansions. */ spin_lock(&vma->vm_mm->page_table_lock); + if (vma->vm_flags & VM_LOCKED) + vma->vm_mm->locked_vm += grow; + vm_stat_account(vma->vm_mm, vma->vm_flags, + vma->vm_file, grow); anon_vma_interval_tree_pre_update_vma(vma); vma->vm_start = address; vma->vm_pgoff -= grow; -- 2.4.3