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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 AD489C433B4 for ; Wed, 21 Apr 2021 17:17:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 83D7961454 for ; Wed, 21 Apr 2021 17:17:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244696AbhDURR5 (ORCPT ); Wed, 21 Apr 2021 13:17:57 -0400 Received: from foss.arm.com ([217.140.110.172]:38466 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241450AbhDURRz (ORCPT ); Wed, 21 Apr 2021 13:17:55 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B0E391424; Wed, 21 Apr 2021 10:17:21 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [10.57.3.41]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 322E73F694; Wed, 21 Apr 2021 10:17:20 -0700 (PDT) Date: Wed, 21 Apr 2021 18:17:15 +0100 From: Mark Rutland To: He Zhe Cc: Catalin Marinas , oleg@redhat.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, paul@paul-moore.com, eparis@redhat.com, linux-audit@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] arm64: ptrace: Add is_syscall_success to handle compat Message-ID: <20210421171715.GA52940@C02TD0UTHF1T.local> References: <20210416075533.7720-1-zhe.he@windriver.com> <20210416123322.GA23184@arm.com> <9b5b340b-66ad-41c9-865e-32724e33a5b8@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9b5b340b-66ad-41c9-865e-32724e33a5b8@windriver.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 20, 2021 at 04:42:53PM +0800, He Zhe wrote: > On 4/16/21 8:33 PM, Catalin Marinas wrote: > > On Fri, Apr 16, 2021 at 03:55:31PM +0800, He Zhe wrote: > >> The general version of is_syscall_success does not handle 32-bit > >> compatible case, which would cause 32-bit negative return code to be > >> recoganized as a positive number later and seen as a "success". > >> > >> Since is_compat_thread is defined in compat.h, implementing > >> is_syscall_success in ptrace.h would introduce build failure due to > >> recursive inclusion of some basic headers like mutex.h. We put the > >> implementation to ptrace.c > >> > >> Signed-off-by: He Zhe > >> --- > >> arch/arm64/include/asm/ptrace.h | 3 +++ > >> arch/arm64/kernel/ptrace.c | 10 ++++++++++ > >> 2 files changed, 13 insertions(+) > >> > >> diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h > >> index e58bca832dff..3c415e9e5d85 100644 > >> --- a/arch/arm64/include/asm/ptrace.h > >> +++ b/arch/arm64/include/asm/ptrace.h > >> @@ -328,6 +328,9 @@ static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc) > >> regs->regs[0] = rc; > >> } > >> > >> +extern inline int is_syscall_success(struct pt_regs *regs); > >> +#define is_syscall_success(regs) is_syscall_success(regs) > >> + > >> /** > >> * regs_get_kernel_argument() - get Nth function argument in kernel > >> * @regs: pt_regs of that context > >> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c > >> index 170f42fd6101..3266201f8c60 100644 > >> --- a/arch/arm64/kernel/ptrace.c > >> +++ b/arch/arm64/kernel/ptrace.c > >> @@ -1909,3 +1909,13 @@ int valid_user_regs(struct user_pt_regs *regs, struct task_struct *task) > >> else > >> return valid_native_regs(regs); > >> } > >> + > >> +inline int is_syscall_success(struct pt_regs *regs) > >> +{ > >> + unsigned long val = regs->regs[0]; > >> + > >> + if (is_compat_thread(task_thread_info(current))) > >> + val = sign_extend64(val, 31); > >> + > >> + return !IS_ERR_VALUE(val); > >> +} > > It's better to use compat_user_mode(regs) here instead of > > is_compat_thread(). It saves us from worrying whether regs are for the > > current context. > > Thanks. I'll use this for v2. > > > > > I think we should change regs_return_value() instead. This function > > seems to be called from several other places and it has the same > > potential problems if called on compat pt_regs. > > IMHO, now that we have had specific function, syscall_get_return_value, to get > syscall return code, we might as well use it. regs_return_value may be left for > where we want internal return code. I found such places below and haven't found > other places that syscall sign extension is concerned about. > > kernel/test_kprobes.c > kernel/trace/trace_kprobe.c > samples/kprobes/kretprobe_example.c FWIW, I agree that we should use syscall_get_return_value(). If we make the common implementation of is_syscall_success() use syscall_get_return_value(), we shouldn't need to write our own implementation, so I'd prefer if we could do that if possible. IIUC regs_get_return_value() was originally meant to be used for kernel regs, and is trying to do something quite different, so having the core code use syscall_get_return_value() makes sense to allow architectures to handle those cases differently. Thanks, Mark.