tests: add a test for the case when there is a helper with a zombie child

v2: drop /bin/ps from test deps
v3: wait for the zombie to make sure it exits
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Acked-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

test/zdtm/static/Makefile

@@ -151,6 +151,7 @@ TST_NOFILE	=				\
 		oom_score_adj			\
 		loginuid			\
 		cgroupns			\
+		helper_zombie_child		\
 #		jobctl00			\
 
 TST_FILE	=				\

test/zdtm/static/helper_zombie_child.c

+#define _GNU_SOURCE
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <signal.h>
+#include <stddef.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#include <sys/prctl.h>
+
+#include "zdtmtst.h"
+
+const char *test_doc	= "Check that a zombie with a helper parent is restored";
+const char *test_author	= "Tycho Andersen <tycho.andersen@canonical.com>";
+
+void setsid_and_fork(int sk)
+{
+	pid_t zombie;
+
+	setsid();
+
+	zombie = fork();
+	if (zombie < 0) {
+		fail("fork");
+		exit(1);
+	}
+
+	if (zombie == 0)
+		exit(0);
+
+	if (waitid(P_PID, zombie, NULL, WNOWAIT | WEXITED) < 0) {
+		fail("waitid");
+		exit(1);
+	}
+
+	if (write(sk, &zombie, sizeof(zombie)) != sizeof(zombie)) {
+		fail("write");
+		exit(1);
+	}
+
+	close(sk);
+
+	exit(0);
+}
+
+int main(int argc, char **argv)
+{
+	pid_t pid, zombie;
+	int status, sk_pair[2];
+
+	if (setenv("ZDTM_NOREAP", "1", 1) < 0) {
+		fail("setenv");
+		return 1;
+	}
+
+	test_init(argc, argv);
+
+	if (socketpair(PF_LOCAL, SOCK_STREAM, 0, sk_pair)) {
+		pr_perror("socketpair");
+		return 1;
+	}
+
+	pid = fork();
+	if (pid < 0) {
+		fail("fork");
+		return 1;
+	}
+
+	if (pid == 0) {
+		close(sk_pair[0]);
+		setsid_and_fork(sk_pair[1]);
+	}
+
+	close(sk_pair[1]);
+
+	if (read(sk_pair[0], &zombie, sizeof(zombie)) != sizeof(zombie)) {
+		fail("read");
+		kill(pid, SIGKILL);
+		return 1;
+	}
+
+	if (waitpid(pid, &status, 0) < 0) {
+		fail("waitpid");
+		return 1;
+	}
+
+	if (!WIFEXITED(status) || WEXITSTATUS(status)) {
+		fail("setsid_and_fork");
+		return 1;
+	}
+
+	if (kill(zombie, 0) < 0) {
+		fail("zombie already dead?");
+		return 1;
+	}
+
+	test_daemon();
+	test_waitsig();
+
+	/* XXX: we don't restore zombies with the right uid right now; they're all root */
+	if (kill(zombie, 0) < 0 && errno != EPERM) {
+		fail("zombie didn't survive restore");
+		return 1;
+	}
+
+	pass();
+	return 0;
+}

test/zdtm/static/helper_zombie_child.desc

+{'flavor': 'ns uns'}