From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752696AbaHUQre (ORCPT ); Thu, 21 Aug 2014 12:47:34 -0400 Received: from mail-oi0-f51.google.com ([209.85.218.51]:49349 "EHLO mail-oi0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751991AbaHUQrd (ORCPT ); Thu, 21 Aug 2014 12:47:33 -0400 MIME-Version: 1.0 In-Reply-To: <1408611405-8943-2-git-send-email-takahiro.akashi@linaro.org> References: <1408611405-8943-1-git-send-email-takahiro.akashi@linaro.org> <1408611405-8943-2-git-send-email-takahiro.akashi@linaro.org> Date: Thu, 21 Aug 2014 11:47:32 -0500 X-Google-Sender-Auth: 9wx2mIW6pcG4IhqymgGWDYjUu7g Message-ID: Subject: Re: [PATCH v6 1/6] arm64: ptrace: add PTRACE_SET_SYSCALL From: Kees Cook To: AKASHI Takahiro Cc: Catalin Marinas , Will Deacon , Deepak Saxena , arndb@arndb.de, "linux-arm-kernel@lists.infradead.org" , linaro-kernel@lists.linaro.org, LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. I wonder if other archs should add this option too. 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 > -- Kees Cook Chrome OS Security From mboxrd@z Thu Jan 1 00:00:00 1970 From: keescook@chromium.org (Kees Cook) Date: Thu, 21 Aug 2014 11:47:32 -0500 Subject: [PATCH v6 1/6] arm64: ptrace: add PTRACE_SET_SYSCALL In-Reply-To: <1408611405-8943-2-git-send-email-takahiro.akashi@linaro.org> References: <1408611405-8943-1-git-send-email-takahiro.akashi@linaro.org> <1408611405-8943-2-git-send-email-takahiro.akashi@linaro.org> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. I wonder if other archs should add this option too. 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 > -- Kees Cook Chrome OS Security