On Thu, Sep 06, 2018 at 06:15:18PM +0200, Jann Horn wrote: > On Thu, Sep 6, 2018 at 5:29 PM Tycho Andersen <tycho@xxxxxxxx> wrote: > > The idea here is that the userspace handler should be able to pass an fd > > back to the trapped task, for example so it can be returned from socket(). > [...] > > diff --git a/Documentation/userspace-api/seccomp_filter.rst b/Documentation/userspace-api/seccomp_filter.rst > > index d1498885c1c7..1c0aab306426 100644 > > --- a/Documentation/userspace-api/seccomp_filter.rst > > +++ b/Documentation/userspace-api/seccomp_filter.rst > > @@ -235,6 +235,9 @@ The interface for a seccomp notification fd consists of two structures: > > __u64 id; > > __s32 error; > > __s64 val; > > + __u8 return_fd; > > + __u32 fd; > > + __u32 fd_flags; > > Normally, syscalls that take an optional file descriptor accept a > signed 32-bit number, with -1 standing for "no file descriptor". Is > there a reason why this uses a separate variable to signal whether an > fd was provided? No real reason other than I looked at the bpf code and they were using __u32 for bpf (but I think in their case the fd args are not optional). I'll switch it to __s32/-1 for the next version. > Apart from that, this patch looks good to me. Thanks, Tycho
