Unverified Commit 56f235da authored by Christian Brauner's avatar Christian Brauner
Browse files

selftests/pidfd: add seventh PIDFD_INFO_EXIT selftest 

Add a selftest for PIDFD_INFO_EXIT behavior.

Link: https://lore.kernel.org/r/20250305-work-pidfs-kill_on_last_close-v3-16-c8c3d8361705@kernel.org


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 1c4f2dbe

tools/testing/selftests/pidfd/.gitignore

+1 −0
Original line number Diff line number Diff line
@@ -9,3 +9,4 @@ pidfd_setns_test 
pidfd_file_handle_test

pidfd_bind_mount

pidfd_info_test

pidfd_exec_helper

tools/testing/selftests/pidfd/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -5,5 +5,7 @@ TEST_GEN_PROGS := pidfd_test pidfd_fdinfo_test pidfd_open_test \ 
	pidfd_poll_test pidfd_wait pidfd_getfd_test pidfd_setns_test \

	pidfd_file_handle_test pidfd_bind_mount pidfd_info_test



TEST_GEN_PROGS_EXTENDED := pidfd_exec_helper



include ../lib.mk

tools/testing/selftests/pidfd/pidfd.h

+7 −0
Original line number Diff line number Diff line
@@ -254,4 +254,11 @@ static inline ssize_t write_nointr(int fd, const void *buf, size_t count) 
	return ret;

}



static inline int sys_execveat(int dirfd, const char *pathname,

			       char *const argv[], char *const envp[],

			       int flags)

{

        return syscall(__NR_execveat, dirfd, pathname, argv, envp, flags);

}



#endif /* __PIDFD_H */

tools/testing/selftests/pidfd/pidfd_exec_helper.c

0 → 100644
+12 −0
Original line number Diff line number Diff line 
#define _GNU_SOURCE

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>



int main(int argc, char *argv[])

{

	if (pause())

		_exit(EXIT_FAILURE);



	_exit(EXIT_SUCCESS);

}

tools/testing/selftests/pidfd/pidfd_info_test.c

+125 −0
Original line number Diff line number Diff line
@@ -369,4 +369,129 @@ TEST_F(pidfd_info, thread_group) 
	EXPECT_EQ(close(pidfd_thread), 0);

}



static void *pidfd_info_thread_exec(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)

{

	pid_t pid_leader, 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, &ipc_sockets[1]))

			syscall(__NR_exit, EXIT_FAILURE);



		/* Make the thread-group leader exit prematurely. */

		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);



	/*

	 * We can poll and wait for the old thread-group leader to exit

	 * using a thread-specific pidfd.

	 *

	 * This only works until the thread has execed. When the thread

	 * has execed it will have taken over the old thread-group

	 * leaders struct pid. Calling poll after the thread execed will

	 * thus block again because a new thread-group has started (Yes,

	 * it's fscked.).

	 */

	fds.events = POLLIN;

	fds.fd = pidfd_leader_thread;

	nevents = poll(&fds, 1, -1);

	ASSERT_EQ(nevents, 1);

	/* The thread-group leader has exited. */

	ASSERT_TRUE(!!(fds.revents & POLLIN));

	/* The thread-group leader hasn't been reaped. */

	ASSERT_FALSE(!!(fds.revents & POLLHUP));



	/* 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);



	/* 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);

	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