Ensure that during a multi-threaded exec and premature thread-group
leader exit no exit notification is generated.
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
---
tools/testing/selftests/pidfd/pidfd_info_test.c | 147 ++++++++++++++++++++++++
1 file changed, 147 insertions(+)
diff --git a/tools/testing/selftests/pidfd/pidfd_info_test.c b/tools/testing/selftests/pidfd/pidfd_info_test.c
index 4169780c9e55..1758a1b0457b 100644
--- a/tools/testing/selftests/pidfd/pidfd_info_test.c
+++ b/tools/testing/selftests/pidfd/pidfd_info_test.c
@@ -542,4 +542,151 @@ TEST_F(pidfd_info, thread_group_exec)
EXPECT_EQ(close(pidfd_thread), 0);
}
+static void *pidfd_info_thread_exec_sane(void *arg)
+{
+ pid_t pid_thread = gettid();
+ int ipc_socket = *(int *)arg;
+
+ /* Inform the grand-parent what the tid of this thread is. */
+ if (write_nointr(ipc_socket, &pid_thread, sizeof(pid_thread)) != sizeof(pid_thread))
+ return NULL;
+
+ if (read_nointr(ipc_socket, &pid_thread, sizeof(pid_thread)) != sizeof(pid_thread))
+ return NULL;
+
+ close(ipc_socket);
+
+ sys_execveat(AT_FDCWD, "pidfd_exec_helper", NULL, NULL, 0);
+ return NULL;
+}
+
+TEST_F(pidfd_info, thread_group_exec_thread)
+{
+ pid_t pid_leader, pid_poller, pid_thread;
+ pthread_t thread;
+ int nevents, pidfd_leader, pidfd_leader_thread, pidfd_thread, ret;
+ int ipc_sockets[2];
+ struct pollfd fds = {};
+ struct pidfd_info info = {
+ .mask = PIDFD_INFO_CGROUPID | PIDFD_INFO_EXIT,
+ };
+
+ ret = socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets);
+ EXPECT_EQ(ret, 0);
+
+ pid_leader = create_child(&pidfd_leader, 0);
+ EXPECT_GE(pid_leader, 0);
+
+ if (pid_leader == 0) {
+ close(ipc_sockets[0]);
+
+ /* The thread will outlive the thread-group leader. */
+ if (pthread_create(&thread, NULL, pidfd_info_thread_exec_sane, &ipc_sockets[1]))
+ syscall(__NR_exit, EXIT_FAILURE);
+
+ /*
+ * Pause the thread-group leader. It will be killed once
+ * the subthread execs.
+ */
+ pause();
+ syscall(__NR_exit, EXIT_SUCCESS);
+ }
+
+ /* Retrieve the tid of the thread. */
+ EXPECT_EQ(close(ipc_sockets[1]), 0);
+ ASSERT_EQ(read_nointr(ipc_sockets[0], &pid_thread, sizeof(pid_thread)), sizeof(pid_thread));
+
+ /* Opening a thread as a PIDFD_THREAD must succeed. */
+ pidfd_thread = sys_pidfd_open(pid_thread, PIDFD_THREAD);
+ ASSERT_GE(pidfd_thread, 0);
+
+ /* Open a thread-specific pidfd for the thread-group leader. */
+ pidfd_leader_thread = sys_pidfd_open(pid_leader, PIDFD_THREAD);
+ ASSERT_GE(pidfd_leader_thread, 0);
+
+ pid_poller = fork();
+ ASSERT_GE(pid_poller, 0);
+ if (pid_poller == 0) {
+ /*
+ * The subthread will now exec. The struct pid of the old
+ * thread-group leader will be assumed by the subthread which
+ * becomes the new thread-group leader. So no exit notification
+ * must be generated. Wait for 5 seconds and call it a success
+ * if no notification has been received.
+ */
+ fds.events = POLLIN;
+ fds.fd = pidfd_leader_thread;
+ nevents = poll(&fds, 1, 10000 /* wait 5 seconds */);
+ if (nevents != 0)
+ _exit(EXIT_FAILURE);
+ if (fds.revents & POLLIN)
+ _exit(EXIT_FAILURE);
+ if (fds.revents & POLLHUP)
+ _exit(EXIT_FAILURE);
+ _exit(EXIT_SUCCESS);
+ }
+
+ /* Now that we've opened a thread-specific pidfd the thread can exec. */
+ ASSERT_EQ(write_nointr(ipc_sockets[0], &pid_thread, sizeof(pid_thread)), sizeof(pid_thread));
+ EXPECT_EQ(close(ipc_sockets[0]), 0);
+ ASSERT_EQ(wait_for_pid(pid_poller), 0);
+
+ /* Wait until the kernel has SIGKILLed the thread. */
+ fds.events = POLLHUP;
+ fds.fd = pidfd_thread;
+ nevents = poll(&fds, 1, -1);
+ ASSERT_EQ(nevents, 1);
+ /* The thread has been reaped. */
+ ASSERT_TRUE(!!(fds.revents & POLLHUP));
+
+ /* Retrieve thread-specific exit info from pidfd. */
+ ASSERT_EQ(ioctl(pidfd_thread, PIDFD_GET_INFO, &info), 0);
+ ASSERT_FALSE(!!(info.mask & PIDFD_INFO_CREDS));
+ ASSERT_TRUE(!!(info.mask & PIDFD_INFO_EXIT));
+ /*
+ * While the kernel will have SIGKILLed the whole thread-group
+ * during exec it will cause the individual threads to exit
+ * cleanly.
+ */
+ ASSERT_TRUE(WIFEXITED(info.exit_code));
+ ASSERT_EQ(WEXITSTATUS(info.exit_code), 0);
+
+ /*
+ * The thread-group leader is still alive, the thread has taken
+ * over its struct pid and thus its pid number.
+ */
+ info.mask = PIDFD_INFO_CGROUPID | PIDFD_INFO_EXIT;
+ ASSERT_EQ(ioctl(pidfd_leader, PIDFD_GET_INFO, &info), 0);
+ ASSERT_TRUE(!!(info.mask & PIDFD_INFO_CREDS));
+ ASSERT_FALSE(!!(info.mask & PIDFD_INFO_EXIT));
+ ASSERT_EQ(info.pid, pid_leader);
+
+ /* Take down the thread-group leader. */
+ EXPECT_EQ(sys_pidfd_send_signal(pidfd_leader, SIGKILL, NULL, 0), 0);
+
+ /*
+ * Afte the exec we're dealing with an empty thread-group so now
+ * we must see an exit notification on the thread-specific pidfd
+ * for the thread-group leader as there's no subthread that can
+ * revive the struct pid.
+ */
+ fds.events = POLLIN;
+ fds.fd = pidfd_leader_thread;
+ nevents = poll(&fds, 1, -1);
+ ASSERT_EQ(nevents, 1);
+ ASSERT_TRUE(!!(fds.revents & POLLIN));
+ ASSERT_FALSE(!!(fds.revents & POLLHUP));
+
+ EXPECT_EQ(sys_waitid(P_PIDFD, pidfd_leader, NULL, WEXITED), 0);
+
+ /* Retrieve exit information for the thread-group leader. */
+ info.mask = PIDFD_INFO_CGROUPID | PIDFD_INFO_EXIT;
+ ASSERT_EQ(ioctl(pidfd_leader, PIDFD_GET_INFO, &info), 0);
+ ASSERT_FALSE(!!(info.mask & PIDFD_INFO_CREDS));
+ ASSERT_TRUE(!!(info.mask & PIDFD_INFO_EXIT));
+
+ EXPECT_EQ(close(pidfd_leader), 0);
+ EXPECT_EQ(close(pidfd_thread), 0);
+}
+
TEST_HARNESS_MAIN
--
2.47.2
