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=-8.4 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 D4FB9C004C9 for ; Tue, 7 May 2019 17:25:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B2CC6206A3 for ; Tue, 7 May 2019 17:25:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727425AbfEGRZV (ORCPT ); Tue, 7 May 2019 13:25:21 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:60408 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726473AbfEGRZV (ORCPT ); Tue, 7 May 2019 13:25:21 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CF4F4A78; Tue, 7 May 2019 10:25:20 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 778373F5AF; Tue, 7 May 2019 10:25:19 -0700 (PDT) Date: Tue, 7 May 2019 18:25:12 +0100 From: Mark Rutland To: Sami Tolvanen Cc: Catalin Marinas , Will Deacon , Kees Cook , Nick Desaulniers , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/3] arm64: use the correct function type for __arm64_sys_ni_syscall Message-ID: <20190507172512.GA35803@lakrids.cambridge.arm.com> References: <20190503191225.6684-1-samitolvanen@google.com> <20190503191225.6684-4-samitolvanen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190503191225.6684-4-samitolvanen@google.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 03, 2019 at 12:12:25PM -0700, Sami Tolvanen wrote: > Calling sys_ni_syscall through a syscall_fn_t pointer trips indirect > call Control-Flow Integrity checking due to a function type > mismatch. Use SYSCALL_DEFINE0 for __arm64_sys_ni_syscall instead and > remove the now unnecessary casts. > > Signed-off-by: Sami Tolvanen > --- > arch/arm64/kernel/sys.c | 14 +++++++++----- > arch/arm64/kernel/sys32.c | 12 ++++++++---- > 2 files changed, 17 insertions(+), 9 deletions(-) > > diff --git a/arch/arm64/kernel/sys.c b/arch/arm64/kernel/sys.c > index b44065fb16160..4f8e8a7237a85 100644 > --- a/arch/arm64/kernel/sys.c > +++ b/arch/arm64/kernel/sys.c > @@ -47,22 +47,26 @@ SYSCALL_DEFINE1(arm64_personality, unsigned int, personality) > return ksys_personality(personality); > } > > +asmlinkage long sys_ni_syscall(void); > + > +SYSCALL_DEFINE0(ni_syscall) > +{ > + return sys_ni_syscall(); > +} I strongly think that we cant to fix up the common definition in kernel/sys_ni.c rather than having a point-hack in arm64. Other architectures (e.g. x86, s390) will want the same for CFI, and I'd like to ensure that our approached don't diverge. I took a quick look, and it looks like it's messy but possible to fix up the core. I also suspect that using SYSCALL_DEFINE0() as it currently stands isn't a great idea, since it'll allow fault injection for unimplemented syscalls, which sounds dubious to me. Thanks, Mark. > + > /* > * Wrappers to pass the pt_regs argument. > */ > #define sys_personality sys_arm64_personality > > -asmlinkage long sys_ni_syscall(const struct pt_regs *); > -#define __arm64_sys_ni_syscall sys_ni_syscall > - > #undef __SYSCALL > #define __SYSCALL(nr, sym) asmlinkage long __arm64_##sym(const struct pt_regs *); > #include > > #undef __SYSCALL > -#define __SYSCALL(nr, sym) [nr] = (syscall_fn_t)__arm64_##sym, > +#define __SYSCALL(nr, sym) [nr] = __arm64_##sym, > > const syscall_fn_t sys_call_table[__NR_syscalls] = { > - [0 ... __NR_syscalls - 1] = (syscall_fn_t)sys_ni_syscall, > + [0 ... __NR_syscalls - 1] = __arm64_sys_ni_syscall, > #include > }; > diff --git a/arch/arm64/kernel/sys32.c b/arch/arm64/kernel/sys32.c > index 0f8bcb7de7008..f8f6c26cfd326 100644 > --- a/arch/arm64/kernel/sys32.c > +++ b/arch/arm64/kernel/sys32.c > @@ -133,17 +133,21 @@ COMPAT_SYSCALL_DEFINE6(aarch32_fallocate, int, fd, int, mode, > return ksys_fallocate(fd, mode, arg_u64(offset), arg_u64(len)); > } > > -asmlinkage long sys_ni_syscall(const struct pt_regs *); > -#define __arm64_sys_ni_syscall sys_ni_syscall > +asmlinkage long sys_ni_syscall(void); > + > +COMPAT_SYSCALL_DEFINE0(ni_syscall) > +{ > + return sys_ni_syscall(); > +} > > #undef __SYSCALL > #define __SYSCALL(nr, sym) asmlinkage long __arm64_##sym(const struct pt_regs *); > #include > > #undef __SYSCALL > -#define __SYSCALL(nr, sym) [nr] = (syscall_fn_t)__arm64_##sym, > +#define __SYSCALL(nr, sym) [nr] = __arm64_##sym, > > const syscall_fn_t compat_sys_call_table[__NR_compat_syscalls] = { > - [0 ... __NR_compat_syscalls - 1] = (syscall_fn_t)sys_ni_syscall, > + [0 ... __NR_compat_syscalls - 1] = __arm64_sys_ni_syscall, > #include > }; > -- > 2.21.0.1020.gf2820cf01a-goog >