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=-10.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=ham 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 14CEFC433E0 for ; Wed, 15 Jul 2020 03:36:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EBB322072D for ; Wed, 15 Jul 2020 03:36:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728386AbgGODgB (ORCPT ); Tue, 14 Jul 2020 23:36:01 -0400 Received: from out03.mta.xmission.com ([166.70.13.233]:42686 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726648AbgGODgB (ORCPT ); Tue, 14 Jul 2020 23:36:01 -0400 Received: from in02.mta.xmission.com ([166.70.13.52]) by out03.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jvYD7-000181-1R; Tue, 14 Jul 2020 21:35:57 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1jvYD5-0005mz-Hq; Tue, 14 Jul 2020 21:35:56 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Christoph Hellwig Cc: Nick Hu , Greentime Hu , Vincent Chen , Paul Walmsley , Palmer Dabbelt , Andrew Morton , Linus Torvalds , linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200714105505.935079-1-hch@lst.de> <20200714105505.935079-7-hch@lst.de> Date: Tue, 14 Jul 2020 22:33:05 -0500 In-Reply-To: <20200714105505.935079-7-hch@lst.de> (Christoph Hellwig's message of "Tue, 14 Jul 2020 12:55:05 +0200") Message-ID: <87v9ip4fm6.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=1jvYD5-0005mz-Hq;;;mid=<87v9ip4fm6.fsf@x220.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18jRvo1LY05IcyELAS/Dyw89Gb+7bU2HOk= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH 6/6] exec: use force_uaccess_begin during exec and exit X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Christoph Hellwig writes: > Both exec and exit want to ensure that the uaccess routines actually do > access user pointers. Use the newly added force_uaccess_begin helper > instead of an open coded set_fs for that to prepare for kernel builds > where set_fs() does not exist. Acked-by: "Eric W. Biederman" Have you played with a tree with all of your patches and placing force_uaccess_begin in init/main.c:start_kernel? Somewhere deep in the arch code we seem to have it all backwards and kernel threads are all set_fs(KERNEL_DS). So just putting a force_uaccess_begin somewhere very early should be enough to switch things around. > Signed-off-by: Christoph Hellwig > --- > fs/exec.c | 7 ++++++- > kernel/exit.c | 2 +- > 2 files changed, 7 insertions(+), 2 deletions(-) > > diff --git a/fs/exec.c b/fs/exec.c > index e6e8a9a7032784..769af470b69124 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -1380,7 +1380,12 @@ int begin_new_exec(struct linux_binprm * bprm) > if (retval) > goto out_unlock; > > - set_fs(USER_DS); > + /* > + * Ensure that the uaccess routines can actually operate on userspace > + * pointers: > + */ > + force_uaccess_begin(); > + > me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD | > PF_NOFREEZE | PF_NO_SETAFFINITY); > flush_thread(); > diff --git a/kernel/exit.c b/kernel/exit.c > index 727150f2810338..17d486a20f0dc6 100644 > --- a/kernel/exit.c > +++ b/kernel/exit.c > @@ -731,7 +731,7 @@ void __noreturn do_exit(long code) > * mm_release()->clear_child_tid() from writing to a user-controlled > * kernel address. > */ > - set_fs(USER_DS); > + force_uaccess_begin(); > > if (unlikely(in_atomic())) { > pr_info("note: %s[%d] exited with preempt_count %d\n",