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. > > 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
