Re: [PATCH v2 3/3] selftests/seccomp: Test SECCOMP_IOCTL_NOTIF_ADDFD

[Tycho Andersen]

On Fri, May 29, 2020 at 06:46:07PM +0000, Sargun Dhillon wrote:
> On Fri, May 29, 2020 at 12:41:51AM -0700, Kees Cook wrote:
> > On Thu, May 28, 2020 at 04:08:58AM -0700, Sargun Dhillon wrote:
> > > +	EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), 0);
> > > +
> > > +	nextid = req.id + 1;
> > > +
> > > +	/* Wait for getppid to be called for the second time */
> > > +	sleep(1);
> > 
> > I always rebel at finding "sleep" in tests. ;) Is this needed? IIUC,
> > userspace will immediately see EINPROGRESS after the NOTIF_SEND
> > finishes, yes?
> > 
> > Otherwise, yes, this looks good.
> > 
> > -- 
> > Kees Cook
> I'm open to better suggestions, but there's a race where if getppid
> is not called before the second SECCOMP_IOCTL_NOTIF_ADDFD is called,
> you will just get an ENOENT, since the notification ID is not found.

Ah, I see. The goal is to test the -EINPROGRESS here.

If you use write() instead of getppid(), and write to a socket, will
that work? The parent can block for the read, and once some thing has
been read it can test for -EINPROGRESS.

The user_notification_signal test does something similar.

Tycho