From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f178.google.com (mail-ig0-f178.google.com [209.85.213.178]) by kanga.kvack.org (Postfix) with ESMTP id 1513D6B0253 for ; Wed, 23 Sep 2015 11:37:21 -0400 (EDT) Received: by igxx6 with SMTP id x6so30346433igx.1 for ; Wed, 23 Sep 2015 08:37:20 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id k89si7256885iod.9.2015.09.23.08.37.20 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 23 Sep 2015 08:37:20 -0700 (PDT) Date: Wed, 23 Sep 2015 17:34:16 +0200 From: Oleg Nesterov Subject: Re: Multiple potential races on vma->vm_flags Message-ID: <20150923153416.GA18973@redhat.com> References: <55EC9221.4040603@oracle.com> <20150907114048.GA5016@node.dhcp.inet.fi> <55F0D5B2.2090205@oracle.com> <20150910083605.GB9526@node.dhcp.inet.fi> <20150911103959.GA7976@node.dhcp.inet.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150911103959.GA7976@node.dhcp.inet.fi> Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: Andrey Konovalov , Sasha Levin , Rik van Riel , Andrew Morton , Dmitry Vyukov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vlastimil Babka , Hugh Dickins On 09/11, Kirill A. Shutemov wrote: > > This one is tricky. I *assume* the mm cannot be generally accessible after > mm_users drops to zero, but I'm not entirely sure about it. > procfs? ptrace? Well, all I can say is that proc/ptrace look fine afaics... This is off-topic, but how about the patch below? Different threads can expand different vma's at the same time under read_lock(mmap_sem), so vma_lock_anon_vma() can't help to serialize "locked_vm += grow". Oleg. --- x/mm/mmap.c +++ x/mm/mmap.c @@ -2146,9 +2146,6 @@ static int acct_stack_growth(struct vm_a 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; } @@ -2210,6 +2207,8 @@ int expand_upwards(struct vm_area_struct * against concurrent vma expansions. */ spin_lock(&vma->vm_mm->page_table_lock); + if (vma->vm_flags & VM_LOCKED) + mm->locked_vm += grow; anon_vma_interval_tree_pre_update_vma(vma); vma->vm_end = address; anon_vma_interval_tree_post_update_vma(vma); @@ -2281,6 +2280,8 @@ int expand_downwards(struct vm_area_stru * against concurrent vma expansions. */ spin_lock(&vma->vm_mm->page_table_lock); + if (vma->vm_flags & VM_LOCKED) + mm->locked_vm += grow; anon_vma_interval_tree_pre_update_vma(vma); vma->vm_start = address; vma->vm_pgoff -= grow; -- 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/ . Don't email: email@kvack.org