From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965998AbbCPQSN (ORCPT ); Mon, 16 Mar 2015 12:18:13 -0400 Received: from forward-corp1f.mail.yandex.net ([95.108.130.40]:43536 "EHLO forward-corp1f.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965272AbbCPQSH (ORCPT ); Mon, 16 Mar 2015 12:18:07 -0400 Authentication-Results: smtpcorp1m.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Message-ID: <5507023B.4090905@yandex-team.ru> Date: Mon, 16 Mar 2015 19:18:03 +0300 From: Konstantin Khlebnikov User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Davidlohr Bueso , Oleg Nesterov CC: linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Al Viro Subject: Re: [PATCH] mm: rcu-protected get_mm_exe_file() References: <20150316131257.32340.36600.stgit@buzz> <20150316140720.GA1859@redhat.com> <1426517419.28068.118.camel@stgolabs.net> In-Reply-To: <1426517419.28068.118.camel@stgolabs.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16.03.2015 17:50, Davidlohr Bueso wrote: > On Mon, 2015-03-16 at 15:07 +0100, Oleg Nesterov wrote: >> 3. and we can remove down_write(mmap_sem) from prctl paths. >> >> Actually we can do this even without xchg() above, but we might >> want to kill MMF_EXE_FILE_CHANGED and test_and_set_bit() check. > > Yeah I was waiting for security folks input about this, otherwise this > still doesn't do it for me as we still have to deal with mmap_sem. > Why? mm->flags are updated atomically. mmap_sem isn't required here. -- Konstantin