zdtm: add sk-unix-restore-fs-share test

Add a ZDTM test case where CRIU uses a helper process to restore
a non-empty process group with a terminated leader and a Unix
domain socket. This reproduces a corner case in which mount
namespace switching can fail during restore:

https://github.com/checkpoint-restore/criu/issues/2687

Signed-off-by: Qiao Ma <mqaio@linux.alibaba.com>
Signed-off-by: Radostin Stoyanov <rstoyanov@fedoraproject.org>

test/zdtm/static/Makefile

@@ -382,6 +382,7 @@ TST_FILE	=				\
 		sk-unix-listen02		\
 		sk-unix-listen03		\
 		sk-unix-listen04		\
+		sk-unix-restore-fs-share	\
 		mnt_ext_file_bind_auto		\
 
 TST_DIR		=				\

test/zdtm/static/sk-unix-restore-fs-share.c

@@ -0,0 +1,196 @@
+#include <stdio.h>
+#include <string.h>
+#include <signal.h>
+#include <unistd.h>
+#include <sys/wait.h>
+#include <sys/mman.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include "zdtmtst.h"
+
+const char *test_doc = "Test non-empty process group with terminated parent and unix socket";
+const char *test_author = "Qiao Ma <mqaio@linux.alibaba.com>";
+
+char *filename;
+TEST_OPTION(filename, string, "socket file name", 1);
+
+static int create_and_connect(void)
+{
+	struct sockaddr_un addr;
+	int client_fd;
+
+	client_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+	if (client_fd == -1) {
+		pr_perror("socket");
+		return -1;
+	}
+
+	memset(&addr, 0, sizeof(addr));
+	addr.sun_family = AF_UNIX;
+	if (snprintf(addr.sun_path, sizeof(addr.sun_path), "%s", filename) >= (int)sizeof(addr.sun_path)) {
+		pr_err("Socket path too long\n");
+		close(client_fd);
+		return -1;
+	}
+
+	if (connect(client_fd, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
+		pr_perror("connect");
+		close(client_fd);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int child(int ready_fd)
+{
+	int listen_fd;
+	struct sockaddr_un addr;
+	int ret = EXIT_FAILURE;
+
+	listen_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+	if (listen_fd == -1) {
+		pr_perror("socket");
+		return EXIT_FAILURE;
+	}
+
+	memset(&addr, 0, sizeof(addr));
+	addr.sun_family = AF_UNIX;
+	if (strlen(filename) >= sizeof(addr.sun_path)) {
+		pr_err("Socket path too long\n");
+		goto cleanup;
+	}
+	strncpy(addr.sun_path, filename, sizeof(addr.sun_path));
+
+	unlink(filename); /* Ignore error if file doesn't exist */
+
+	if (bind(listen_fd, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
+		pr_perror("bind");
+		goto cleanup;
+	}
+
+	if (listen(listen_fd, 5) == -1) {
+		pr_perror("listen");
+		goto cleanup;
+	}
+
+	if (create_and_connect() != 0) {
+		pr_err("Failed to create and connect\n");
+		goto cleanup;
+	}
+
+	/* Signal parent that socket is ready */
+	if (write(ready_fd, "1", 1) != 1) {
+		pr_perror("write ready_fd");
+		goto cleanup;
+	}
+
+	/* Wait indefinitely */
+	pause();
+
+	ret = EXIT_SUCCESS;
+cleanup:
+	if (listen_fd != -1)
+		close(listen_fd);
+	unlink(filename);
+
+	return ret;
+}
+
+static int zombie_leader(int *cpid)
+{
+	char buf;
+	pid_t pid;
+	int pipefd[2];
+
+	if (pipe(pipefd) == -1) {
+		pr_perror("pipe");
+		return EXIT_FAILURE;
+	}
+
+	if (setpgid(0, 0) == -1) {
+		pr_perror("setpgid");
+		return EXIT_FAILURE;
+	}
+
+	pid = fork();
+	if (pid < 0) {
+		pr_perror("Failed to fork child");
+		return EXIT_FAILURE;
+	}
+
+	if (pid == 0) {
+		/* Close read end */
+		close(pipefd[0]);
+		exit(child(pipefd[1]));
+	}
+
+	/* Close write end in parent */
+	close(pipefd[1]);
+
+	/* Wait for child to set up socket */
+	if (read(pipefd[0], &buf, 1) != 1) {
+		pr_err("Failed to receive readiness signal from child\n");
+		close(pipefd[0]);
+		return EXIT_FAILURE;
+	}
+	close(pipefd[0]);
+
+	*cpid = pid;
+	return EXIT_SUCCESS;
+}
+
+int main(int argc, char **argv)
+{
+	int ret = EXIT_FAILURE, status;
+	pid_t pid;
+	int *cpid;
+
+	test_init(argc, argv);
+
+	cpid = mmap(NULL, sizeof(int), PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED, -1, 0);
+	if (cpid == MAP_FAILED) {
+		pr_perror("mmap");
+		return EXIT_FAILURE;
+	}
+	*cpid = 0;
+
+	pid = fork();
+	if (pid < 0) {
+		pr_perror("Failed to fork zombie");
+		goto out;
+	}
+
+	if (pid == 0)
+		exit(zombie_leader(cpid));
+
+	if (waitpid(pid, &status, 0) < 0) {
+		pr_perror("Failed to waitpid zombie");
+		goto out;
+	}
+
+	if (!WIFEXITED(status) || WEXITSTATUS(status) != EXIT_SUCCESS) {
+		pr_err("Unexpected exit code: %d\n", WEXITSTATUS(status));
+		goto out;
+	}
+
+	if (!*cpid) {
+		pr_err("Don't know grandchild's pid\n");
+		goto out;
+	}
+
+	test_daemon();
+	test_waitsig();
+
+	ret = EXIT_SUCCESS;
+	pass();
+out:
+	/* Clean up */
+	if (*cpid)
+		kill(*cpid, SIGKILL);
+
+	munmap(cpid, sizeof(int));
+
+	return ret;
+}

test/zdtm/static/sk-unix-restore-fs-share.desc

@@ -0,0 +1 @@
+{'flavor': 'ns uns'}