On Wed, Jul 16, 2014 at 1:21 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> On Tue, Jul 15, 2014 at 12:32 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>>
>> +
>> + ret = seccomp_phase1(&sd);
>> + if (ret == SECCOMP_PHASE1_SKIP) {
>> + regs->orig_ax = -ENOSYS;
>
> Before, seccomp didn't touch orig_ax on a skip. I don't see any
> problem with this, and it's probably more clear this way, but are you
> sure there aren't unexpected side-effects from this?
It's necessary to cause the syscall to be skipped -- see syscall_trace_enter.
That being said, setting it to -ENOSYS is nonsense and probably
confused you at least as much as it confused me. It should be
regs->orig_ax = -1.
--Andy
