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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,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 63286C433DF for ; Mon, 8 Jun 2020 14:59:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 411212074B for ; Mon, 8 Jun 2020 14:59:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730129AbgFHO67 (ORCPT ); Mon, 8 Jun 2020 10:58:59 -0400 Received: from isilmar-4.linta.de ([136.243.71.142]:42582 "EHLO isilmar-4.linta.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730101AbgFHO67 (ORCPT ); Mon, 8 Jun 2020 10:58:59 -0400 Received: from light.dominikbrodowski.net (brodo.linta [10.1.0.102]) by isilmar-4.linta.de (Postfix) with ESMTPSA id 9942F2004D0; Mon, 8 Jun 2020 14:58:57 +0000 (UTC) Received: by light.dominikbrodowski.net (Postfix, from userid 1000) id 44D6C201F7; Mon, 8 Jun 2020 16:58:42 +0200 (CEST) Date: Mon, 8 Jun 2020 16:58:42 +0200 From: Dominik Brodowski To: Catalin Marinas Cc: Wang ShaoBo , huawei.libin@huawei.com, cj.chengjian@huawei.com, xiexiuqi@huawei.com, mark.rutland@arm.com, hch@infradead.org, wcohen@redhat.com, linux-kernel@vger.kernel.org, mtk.manpages@gmail.com, wezhang@redhat.com, gregkh@linuxfoundation.org, Will Deacon Subject: Re: [RESEND PATCH] sys_personality: Add optional arch hook arch_check_personality Message-ID: <20200608145842.GA716055@light.dominikbrodowski.net> References: <20200608024925.42510-1-bobo.shaobowang@huawei.com> <20200608094640.GA13596@gaia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200608094640.GA13596@gaia> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 08, 2020 at 10:46:41AM +0100, Catalin Marinas wrote: > On Mon, Jun 08, 2020 at 10:49:25AM +0800, Wang ShaoBo wrote: > > Currently arm64 personality syscall uses wrapper __arm64_sys_personality > > to redirect to __arm64_sys_arm64_personality, it's easily confused, > > Whereas using an normal hook arch_check_personality() can reject > > additional settings like this for special case of different architectures. > > > > This makes code clean and easier for subsequent modification. > > Do you plan to add more stuff here? Curious what triggered this patch. > > > diff --git a/arch/arm64/kernel/sys.c b/arch/arm64/kernel/sys.c > > index d5ffaaab31a7..5c01816d7a77 100644 > > --- a/arch/arm64/kernel/sys.c > > +++ b/arch/arm64/kernel/sys.c > > @@ -28,12 +28,13 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len, > > return ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT); > > } > > > > -SYSCALL_DEFINE1(arm64_personality, unsigned int, personality) > > +int arch_check_personality(unsigned int personality) > > { > > if (personality(personality) == PER_LINUX32 && > > !system_supports_32bit_el0()) > > return -EINVAL; > > - return ksys_personality(personality); > > + > > + return 0; > > } > > We use the ksys_* pattern in other places as well, so this wouldn't be > something new. > > > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h > > index 1815065d52f3..3dbbad498027 100644 > > --- a/include/linux/syscalls.h > > +++ b/include/linux/syscalls.h > > @@ -1393,16 +1393,6 @@ static inline long ksys_truncate(const char __user *pathname, loff_t length) > > return do_sys_truncate(pathname, length); > > } > > > > -static inline unsigned int ksys_personality(unsigned int personality) > > -{ > > - unsigned int old = current->personality; > > - > > - if (personality != 0xffffffff) > > - set_personality(personality); > > - > > - return old; > > -} > > - > > /* for __ARCH_WANT_SYS_IPC */ > > long ksys_semtimedop(int semid, struct sembuf __user *tsops, > > unsigned int nsops, > > diff --git a/kernel/exec_domain.c b/kernel/exec_domain.c > > index 33f07c5f2515..f3682f4bf205 100644 > > --- a/kernel/exec_domain.c > > +++ b/kernel/exec_domain.c > > @@ -35,9 +35,21 @@ static int __init proc_execdomains_init(void) > > module_init(proc_execdomains_init); > > #endif > > > > +int __weak arch_check_personality(unsigned int personality) > > +{ > > + return 0; > > +} > > + > > SYSCALL_DEFINE1(personality, unsigned int, personality) > > { > > - unsigned int old = current->personality; > > + int err; > > + unsigned int old; > > + > > + err = arch_check_personality(personality); > > + if (err) > > + return err; > > + > > + old = current->personality; > > I'm surprised that the generic sys_personality() doesn't call > ksys_personality() directly but rather duplicates the code. It was the other way round, and the duplication is based on a suggestion by Christoph Hellwig IIRC, https://lore.kernel.org/lkml/20180514120756.GA11638@infradead.org/ Thanks, Dominik