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:

quoted

On Thu, May 28, 2020 at 04:08:58AM -0700, Sargun Dhillon wrote:

quoted

+	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.

The other approach is to "poll" the child, and wait for it to enter
the second syscall. Calling receive beforehand doesn't work because
it moves the state of the notification in the kernel to received,
and then the kernel doesn't error with EINPROGRESS.

For tests, I prefer polling. How about adding a busy-loop
(with a iteration-bounded small usleep) that just calls
SECCOMP_IOCTL_NOTIF_ID_VALID until it's valid?

-- 
Kees Cook