From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E39BAC28CBC for ; Sat, 9 May 2020 14:20:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BAECE21473 for ; Sat, 9 May 2020 14:20:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727918AbgEIOUp (ORCPT ); Sat, 9 May 2020 10:20:45 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:50696 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727092AbgEIOUo (ORCPT ); Sat, 9 May 2020 10:20:44 -0400 Received: from in01.mta.xmission.com ([166.70.13.51]) by out01.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jXQLJ-0006Tb-Ur; Sat, 09 May 2020 08:20:41 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1jXQLI-0001r0-SE; Sat, 09 May 2020 08:20:41 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Kees Cook Cc: linux-kernel@vger.kernel.org, Linus Torvalds , Oleg Nesterov , Jann Horn , Greg Ungerer , Rob Landley , Bernd Edlinger , linux-fsdevel@vger.kernel.org, Al Viro , Alexey Dobriyan , Andrew Morton References: <87h7wujhmz.fsf@x220.int.ebiederm.org> <87sgga6ze4.fsf@x220.int.ebiederm.org> <875zd66za3.fsf_-_@x220.int.ebiederm.org> <202005082213.8BDD4AC0CC@keescook> Date: Sat, 09 May 2020 09:17:11 -0500 In-Reply-To: <202005082213.8BDD4AC0CC@keescook> (Kees Cook's message of "Fri, 8 May 2020 22:15:43 -0700") Message-ID: <87tv0p2nx4.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1jXQLI-0001r0-SE;;;mid=<87tv0p2nx4.fsf@x220.int.ebiederm.org>;;;hst=in01.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18A1U/jWwxjIXHnvSgRraar1VS0tQcBrZU= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH 4/6] exec: Run sync_mm_rss before taking exec_update_mutex X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Kees Cook writes: > $ git grep exec_mm_release > fs/exec.c: exec_mm_release(tsk, old_mm); > include/linux/sched/mm.h:extern void exec_mm_release(struct task_struct *, struct mm_struct *); > kernel/fork.c:void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm) > > kernel/fork.c: > > void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm) > { > futex_exit_release(tsk); > mm_release(tsk, mm); > } > > void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm) > { > futex_exec_release(tsk); > mm_release(tsk, mm); > } > > $ git grep exit_mm_release > include/linux/sched/mm.h:extern void exit_mm_release(struct task_struct *, struct mm_struct *); > kernel/exit.c: exit_mm_release(current, mm); > kernel/fork.c:void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm) > > kernel/exit.c: > > exit_mm_release(current, mm); > if (!mm) > return; > sync_mm_rss(mm); > > It looks to me like both exec_mm_release() and exit_mm_release() could > easily have the sync_mm_rss(...) folded into their function bodies and > removed from the callers. *shrug* Well it would have to be all of: if (mm) sync_mm_rss(mm); I remember reading through exit_mm_release and seeing that nothing actually depended upon a non-NULL mm. Unless you have clear_child_tid set. I am not up to speed on that part of the mm layer right now to know if it is a good idea to put sync_mm_rss in exit_mm_release but at a quick look it feels like it. Eric