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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5E923C433EF for ; Thu, 17 Feb 2022 22:54:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229986AbiBQWyc (ORCPT ); Thu, 17 Feb 2022 17:54:32 -0500 Received: from gmail-smtp-in.l.google.com ([23.128.96.19]:44650 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229496AbiBQWya (ORCPT ); Thu, 17 Feb 2022 17:54:30 -0500 X-Greylist: delayed 1037 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Thu, 17 Feb 2022 14:54:12 PST Received: from out01.mta.xmission.com (out01.mta.xmission.com [166.70.13.231]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3EFEB257DDA; Thu, 17 Feb 2022 14:54:12 -0800 (PST) Received: from in02.mta.xmission.com ([166.70.13.52]:48942) by out01.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1nKpOJ-001bK3-23; Thu, 17 Feb 2022 15:36:47 -0700 Received: from ip68-227-174-4.om.om.cox.net ([68.227.174.4]:32906 helo=email.froward.int.ebiederm.org.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1nKpOG-00GKIm-Md; Thu, 17 Feb 2022 15:36:46 -0700 From: "Eric W. Biederman" To: Arnd Bergmann Cc: Linus Torvalds , Christoph Hellwig , linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, arnd@arndb.de, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, linux@armlinux.org.uk, will@kernel.org, guoren@kernel.org, bcain@codeaurora.org, geert@linux-m68k.org, monstr@monstr.eu, tsbogend@alpha.franken.de, nickhu@andestech.com, green.hu@gmail.com, dinguyen@kernel.org, shorne@gmail.com, deller@gmx.de, mpe@ellerman.id.au, peterz@infradead.org, mingo@redhat.com, mark.rutland@arm.com, hca@linux.ibm.com, dalias@libc.org, davem@davemloft.net, richard@nod.at, x86@kernel.org, jcmvbkbc@gmail.com, akpm@linux-foundation.org, ardb@kernel.org, linux-alpha@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-xtensa@linux-xtensa.org References: <20220216131332.1489939-1-arnd@kernel.org> <20220216131332.1489939-19-arnd@kernel.org> Date: Thu, 17 Feb 2022 16:36:20 -0600 In-Reply-To: <20220216131332.1489939-19-arnd@kernel.org> (Arnd Bergmann's message of "Wed, 16 Feb 2022 14:13:32 +0100") Message-ID: <8735khi0ij.fsf@email.froward.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1nKpOG-00GKIm-Md;;;mid=<8735khi0ij.fsf@email.froward.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.227.174.4;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/V+0C7NWKuSkdwXmdluwhE5ZIu3hq7L5I= X-SA-Exim-Connect-IP: 68.227.174.4 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH v2 18/18] uaccess: drop maining CONFIG_SET_FS users X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org Arnd Bergmann writes: > From: Arnd Bergmann > > There are no remaining callers of set_fs(), so CONFIG_SET_FS > can be removed globally, along with the thread_info field and > any references to it. > > This turns access_ok() into a cheaper check against TASK_SIZE_MAX. > > With CONFIG_SET_FS gone, so drop all remaining references to > set_fs()/get_fs(), mm_segment_t and uaccess_kernel(). For the bits I have looked at recently, and think I understand. Acked-by: "Eric W. Biederman" > > Signed-off-by: Arnd Bergmann > --- > fs/exec.c | 6 -- > kernel/exit.c | 14 ----- > kernel/kthread.c | 5 -- > > diff --git a/fs/exec.c b/fs/exec.c > index 79f2c9483302..bc68a0c089ac 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -1303,12 +1303,6 @@ int begin_new_exec(struct linux_binprm * bprm) > if (retval) > goto out_unlock; > > - /* > - * Ensure that the uaccess routines can actually operate on userspace > - * pointers: > - */ > - force_uaccess_begin(); > - > if (me->flags & PF_KTHREAD) > free_kthread_struct(me); > me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD | > diff --git a/kernel/exit.c b/kernel/exit.c > index b00a25bb4ab9..0884a75bc2f8 100644 > --- a/kernel/exit.c > +++ b/kernel/exit.c > @@ -737,20 +737,6 @@ void __noreturn do_exit(long code) > > WARN_ON(blk_needs_flush_plug(tsk)); > > - /* > - * If do_dead is called because this processes oopsed, it's possible > - * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before > - * continuing. Amongst other possible reasons, this is to prevent > - * mm_release()->clear_child_tid() from writing to a user-controlled > - * kernel address. > - * > - * On uptodate architectures force_uaccess_begin is a noop. On > - * architectures that still have set_fs/get_fs in addition to handling > - * oopses handles kernel threads that run as set_fs(KERNEL_DS) by > - * default. > - */ > - force_uaccess_begin(); > - > kcov_task_exit(tsk); > > coredump_task_exit(tsk); > diff --git a/kernel/kthread.c b/kernel/kthread.c > index 38c6dd822da8..16c2275d4b50 100644 > --- a/kernel/kthread.c > +++ b/kernel/kthread.c > @@ -55,7 +55,6 @@ struct kthread { > int result; > int (*threadfn)(void *); > void *data; > - mm_segment_t oldfs; > struct completion parked; > struct completion exited; > #ifdef CONFIG_BLK_CGROUP > @@ -1441,8 +1440,6 @@ void kthread_use_mm(struct mm_struct *mm) > mmdrop(active_mm); > else > smp_mb(); > - > - to_kthread(tsk)->oldfs = force_uaccess_begin(); > } > EXPORT_SYMBOL_GPL(kthread_use_mm); > > @@ -1457,8 +1454,6 @@ void kthread_unuse_mm(struct mm_struct *mm) > WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD)); > WARN_ON_ONCE(!tsk->mm); > > - force_uaccess_end(to_kthread(tsk)->oldfs); > - > task_lock(tsk); > /* > * When a kthread stops operating on an address space, the loop