Re: [PATCH v7 2/2] selftests: add tests for pidfd_send_signal()

On Tue, Jan 08, 2019 at 11:54:15AM -0600, Serge E. Hallyn wrote:

On Tue, Jan 08, 2019 at 10:53:06AM -0700, Tycho Andersen wrote:

quoted

On Wed, Jan 02, 2019 at 05:16:54PM +0100, Christian Brauner wrote:

quoted

+			/*
+			 * Stop the child so we can inspect whether we have
+			 * recycled pid PID_RECYCLE.
+			 */
+			close(pipe_fds[0]);
+			ret = kill(recycled_pid, SIGSTOP);
+			close(pipe_fds[1]);
+			if (ret) {
+				(void)wait_for_pid(recycled_pid);
+				_exit(PIDFD_ERROR);
+			}

Sorry for being late to the party, but I wonder if this whole thing
couldn't be simplified with /proc/sys/kenrel/ns_last_pid?

no, bc it's not namespaced :)

Huh? It looks like it is...

static int pid_ns_ctl_handler(struct ctl_table *table, int write,
                void __user *buffer, size_t *lenp, loff_t *ppos)
{
        struct pid_namespace *pid_ns = task_active_pid_ns(current);
        struct ctl_table tmp = *table;
        int ret, next;

        if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
                return -EPERM;

        ...

Tycho