repro_ipc_ns_bug.c

#define _GNU_SOURCE
#include <fcntl.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>

static const int NUM_KEEP = 5;

int main(void)
{
	for (int i = 0; i < NUM_KEEP; i++) {
		pid_t pid = fork();
		if (pid < 0) {
			perror("fork");
			return EXIT_FAILURE;
		}
		if (pid == 0) {
			if (unshare(CLONE_NEWIPC) < 0) {
				perror("unshare");
				_exit(EXIT_FAILURE);
			}
			for (;;)
				pause();
		}
	}

	for (;;) {
		pid_t pid = fork();
		if (pid < 0) {
			perror("fork");
			return EXIT_FAILURE;
		}
		if (pid == 0) {
			if (unshare(CLONE_NEWIPC) < 0) {
				perror("unshare");
				_exit(EXIT_FAILURE);
			}
			_exit(EXIT_SUCCESS);
		}
		int wstatus;
		if (waitpid(pid, &wstatus, 0) < 0) {
			perror("waitpid");
			return EXIT_FAILURE;
		}
		if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) != EXIT_SUCCESS)
			sleep(1);
	}
}