On Fri, Aug 22, 2014 at 01:35:17AM +0100, AKASHI Takahiro wrote: > On 08/22/2014 02:08 AM, Kees Cook wrote: > > On Thu, Aug 21, 2014 at 3:56 AM, AKASHI Takahiro > > <takahiro.aka...@linaro.org> wrote: > >> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c > >> index 8876049..c54dbcc 100644 > >> --- a/arch/arm64/kernel/ptrace.c > >> +++ b/arch/arm64/kernel/ptrace.c > >> @@ -1121,9 +1121,29 @@ static void tracehook_report_syscall(struct pt_regs > >> *regs, > >> > >> asmlinkage int syscall_trace_enter(struct pt_regs *regs) > >> { > >> + unsigned int saved_syscallno = regs->syscallno; > >> + > >> if (test_thread_flag(TIF_SYSCALL_TRACE)) > >> tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER); > >> > >> + if (IS_SKIP_SYSCALL(regs->syscallno)) { > >> + /* > >> + * RESTRICTION: we can't modify a return value of user > >> + * issued syscall(-1) here. In order to ease this flavor, > >> + * we need to treat whatever value in x0 as a return value, > >> + * but this might result in a bogus value being returned. > >> + */ > >> + /* > >> + * NOTE: syscallno may also be set to -1 if fatal signal is > >> + * detected in tracehook_report_syscall_entry(), but since > >> + * a value set to x0 here is not used in this case, we may > >> + * neglect the case. > >> + */ > >> + if (!test_thread_flag(TIF_SYSCALL_TRACE) || > >> + (IS_SKIP_SYSCALL(saved_syscallno))) > >> + regs->regs[0] = -ENOSYS; > >> + } > >> + > > > > I don't have a runtime environment yet for arm64, so I can't test this > > directly myself, so I'm just trying to eyeball this. :) > > > > Once the seccomp logic is added here, I don't think using -2 as a > > special value will work. Doesn't this mean the Oops is possible by the > > user issuing a "-2" syscall? As in, if TIF_SYSCALL_WORK is set, and > > the user passed -2 as the syscall, audit will be called only on entry, > > and then skipped on exit? > > Oops, you're absolutely right. I didn't think of this case. > syscall_trace_enter() should not return a syscallno directly, but always > return -1 if syscallno < 0. (except when secure_computing() returns with -1) > This also implies that tracehook_report_syscall() should also have a return > value. > > Will, is this fine with you?
Well, the first thing that jumps out at me is why this is being done completely differently for arm64 and arm. I thought adding the new ptrace requests would reconcile the differences? Will -- 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/