Re: [PATCH v6 4/5] seccomp: add support for passing fds via USER_NOTIF

[Tycho Andersen]

On Thu, Sep 20, 2018 at 07:18:45PM -0700, Andy Lutomirski wrote:
> Hmm.  This does mean that we need a test case for a user notifier
> returning -ERESTARTSYS.  It should Just Work (tm), but those are
> famous last words.

Just to confirm, I've got a test case that works like this:

1. fork and install a SIGUSR1 handler
2. tracee does a syscall that gets trapped
3. send SIGUSR1
4. respond from the listener with -ERESTARTSYS
5. see another of the same syscall, even though the tracee still thinks
   its in the first one
6. respond with something reasonable, the tracee sees this response

I think that's the intended behavior. Note that when the listener
responds with -ERESTARTSYS and there is no signal pending, the task
just dies. That might be reasonable, I'm not sure.

Tycho