From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753578AbaHVATW (ORCPT ); Thu, 21 Aug 2014 20:19:22 -0400 Received: from mail-pd0-f181.google.com ([209.85.192.181]:53978 "EHLO mail-pd0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752063AbaHVATV (ORCPT ); Thu, 21 Aug 2014 20:19:21 -0400 Message-ID: <53F68C81.6020807@linaro.org> Date: Fri, 22 Aug 2014 09:19:13 +0900 From: AKASHI Takahiro User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Kees Cook CC: Catalin Marinas , Will Deacon , Deepak Saxena , arndb@arndb.de, "linux-arm-kernel@lists.infradead.org" , linaro-kernel@lists.linaro.org, LKML Subject: Re: [PATCH v6 1/6] arm64: ptrace: add PTRACE_SET_SYSCALL References: <1408611405-8943-1-git-send-email-takahiro.akashi@linaro.org> <1408611405-8943-2-git-send-email-takahiro.akashi@linaro.org> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/22/2014 01:47 AM, Kees Cook wrote: > On Thu, Aug 21, 2014 at 3:56 AM, AKASHI Takahiro > wrote: >> To allow tracer to be able to change/skip a system call by re-writing >> a syscall number, there are several approaches: >> >> (1) modify x8 register with ptrace(PTRACE_SETREGSET), and handle this case >> later on in syscall_trace_enter(), or >> (2) support ptrace(PTRACE_SET_SYSCALL) as on arm >> >> Thinking of the fact that user_pt_regs doesn't expose 'syscallno' to >> tracer as well as that secure_computing() expects a changed syscall number >> to be visible, especially case of -1, before this function returns in >> syscall_trace_enter(), we'd better take (2). >> >> Signed-off-by: AKASHI Takahiro > > Thanks, I like having this on both arm and arm64. Yeah, having this simplified the code of syscall_trace_enter() a bit, but also imposes some restriction on arm64, too. > I wonder if other archs should add this option too. Do you think so? I assumed that SET_SYSCALL is to be avoided if possible. I also think that SET_SYSCALL should take an extra argument for a return value just in case of -1 (or we have SKIP_SYSCALL?). -Takahiro AKASHI > Reviewed-by: Kees Cook > >> --- >> arch/arm64/include/uapi/asm/ptrace.h | 1 + >> arch/arm64/kernel/ptrace.c | 14 +++++++++++++- >> 2 files changed, 14 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h >> index 6913643..49c6174 100644 >> --- a/arch/arm64/include/uapi/asm/ptrace.h >> +++ b/arch/arm64/include/uapi/asm/ptrace.h >> @@ -23,6 +23,7 @@ >> >> #include >> >> +#define PTRACE_SET_SYSCALL 23 >> >> /* >> * PSR bits >> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c >> index 0310811..8876049 100644 >> --- a/arch/arm64/kernel/ptrace.c >> +++ b/arch/arm64/kernel/ptrace.c >> @@ -1077,7 +1077,19 @@ const struct user_regset_view *task_user_regset_view(struct task_struct *task) >> long arch_ptrace(struct task_struct *child, long request, >> unsigned long addr, unsigned long data) >> { >> - return ptrace_request(child, request, addr, data); >> + int ret; >> + >> + switch (request) { >> + case PTRACE_SET_SYSCALL: >> + task_pt_regs(child)->syscallno = data; >> + ret = 0; >> + break; >> + default: >> + ret = ptrace_request(child, request, addr, data); >> + break; >> + } >> + >> + return ret; >> } >> >> enum ptrace_syscall_dir { >> -- >> 1.7.9.5 >> > > > From mboxrd@z Thu Jan 1 00:00:00 1970 From: takahiro.akashi@linaro.org (AKASHI Takahiro) Date: Fri, 22 Aug 2014 09:19:13 +0900 Subject: [PATCH v6 1/6] arm64: ptrace: add PTRACE_SET_SYSCALL In-Reply-To: References: <1408611405-8943-1-git-send-email-takahiro.akashi@linaro.org> <1408611405-8943-2-git-send-email-takahiro.akashi@linaro.org> Message-ID: <53F68C81.6020807@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 08/22/2014 01:47 AM, Kees Cook wrote: > On Thu, Aug 21, 2014 at 3:56 AM, AKASHI Takahiro > wrote: >> To allow tracer to be able to change/skip a system call by re-writing >> a syscall number, there are several approaches: >> >> (1) modify x8 register with ptrace(PTRACE_SETREGSET), and handle this case >> later on in syscall_trace_enter(), or >> (2) support ptrace(PTRACE_SET_SYSCALL) as on arm >> >> Thinking of the fact that user_pt_regs doesn't expose 'syscallno' to >> tracer as well as that secure_computing() expects a changed syscall number >> to be visible, especially case of -1, before this function returns in >> syscall_trace_enter(), we'd better take (2). >> >> Signed-off-by: AKASHI Takahiro > > Thanks, I like having this on both arm and arm64. Yeah, having this simplified the code of syscall_trace_enter() a bit, but also imposes some restriction on arm64, too. > I wonder if other archs should add this option too. Do you think so? I assumed that SET_SYSCALL is to be avoided if possible. I also think that SET_SYSCALL should take an extra argument for a return value just in case of -1 (or we have SKIP_SYSCALL?). -Takahiro AKASHI > Reviewed-by: Kees Cook > >> --- >> arch/arm64/include/uapi/asm/ptrace.h | 1 + >> arch/arm64/kernel/ptrace.c | 14 +++++++++++++- >> 2 files changed, 14 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h >> index 6913643..49c6174 100644 >> --- a/arch/arm64/include/uapi/asm/ptrace.h >> +++ b/arch/arm64/include/uapi/asm/ptrace.h >> @@ -23,6 +23,7 @@ >> >> #include >> >> +#define PTRACE_SET_SYSCALL 23 >> >> /* >> * PSR bits >> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c >> index 0310811..8876049 100644 >> --- a/arch/arm64/kernel/ptrace.c >> +++ b/arch/arm64/kernel/ptrace.c >> @@ -1077,7 +1077,19 @@ const struct user_regset_view *task_user_regset_view(struct task_struct *task) >> long arch_ptrace(struct task_struct *child, long request, >> unsigned long addr, unsigned long data) >> { >> - return ptrace_request(child, request, addr, data); >> + int ret; >> + >> + switch (request) { >> + case PTRACE_SET_SYSCALL: >> + task_pt_regs(child)->syscallno = data; >> + ret = 0; >> + break; >> + default: >> + ret = ptrace_request(child, request, addr, data); >> + break; >> + } >> + >> + return ret; >> } >> >> enum ptrace_syscall_dir { >> -- >> 1.7.9.5 >> > > >