Re: [PATCH v7 5/6] seccomp: add a way to pass FDs via a notification fd

[Tycho Andersen]

On Thu, Sep 27, 2018 at 09:28:07PM +0200, Jann Horn wrote:
> On Thu, Sep 27, 2018 at 5:11 PM Tycho Andersen <tycho@xxxxxxxx> wrote:
> > This patch adds a way to insert FDs into the tracee's process (also
> > close/overwrite fds for the tracee). This functionality is necessary to
> > mock things like socketpair() or dup2() or similar, but since it depends on
> > external (vfs) patches, I've left it as a separate patch as before so the
> > core functionality can still be merged while we argue about this. Except
> > this time it doesn't add any ugliness to the API :)
> [...]
> > +static long seccomp_notify_put_fd(struct seccomp_filter *filter,
> > +                                 unsigned long arg)
> > +{
> > +       struct seccomp_notif_put_fd req;
> > +       void __user *buf = (void __user *)arg;
> > +       struct seccomp_knotif *knotif = NULL;
> > +       long ret;
> > +
> > +       if (copy_from_user(&req, buf, sizeof(req)))
> > +               return -EFAULT;
> > +
> > +       if (req.fd < 0 && req.to_replace < 0)
> > +               return -EINVAL;
> > +
> > +       ret = mutex_lock_interruptible(&filter->notify_lock);
> > +       if (ret < 0)
> > +               return ret;
> > +
> > +       ret = -ENOENT;
> > +       list_for_each_entry(knotif, &filter->notif->notifications, list) {
> > +               struct file *file = NULL;
> > +
> > +               if (knotif->id != req.id)
> > +                       continue;
> 
> Are you intentionally permitting non-SENT states here? It shouldn't
> make a big difference, but I think it'd be nice to at least block the
> use of notifications in SECCOMP_NOTIFY_REPLIED state.

Agreed, I'll block everything besides REPLIED.

Tycho