On Tue, Aug 26, 2014 at 10:32 PM, AKASHI Takahiro <takahiro.aka...@linaro.org> wrote: > Kees, > > > On 08/27/2014 02:46 AM, Will Deacon wrote: >> >> On Fri, Aug 22, 2014 at 01:19:13AM +0100, AKASHI Takahiro wrote: >>> >>> On 08/22/2014 01:47 AM, Kees Cook wrote: >>>> >>>> On Thu, Aug 21, 2014 at 3:56 AM, AKASHI Takahiro >>>> <takahiro.aka...@linaro.org> 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 <takahiro.aka...@linaro.org> >>>> >>>> >>>> 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?). >> >> >> I think we should propose this as a new request in the generic ptrace >> code. >> We can have an architecture-hook for actually setting the syscall, and >> allow >> architectures to define their own implementation of the request so they >> can >> be moved over one by one. > > > What do you think about this request?
That sounds fine -- it doesn't need to be part of this series. I was just noticing this was a common issue across multiple architectures. -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
