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selftests/pidfd: add sixth PIDFD_INFO_EXIT selftest

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Add a selftest for PIDFD_INFO_EXIT behavior.

Link: https://lore.kernel.org/r/20250305-work-pidfs-kill_on_last_close-v3-15-c8c3d8361705@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2025-03-05 11:08:25 +01:00
parent 2adf6ca638
commit 1c4f2dbe42
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GPG Key ID: 91C61BC06578DCA2
2 changed files with 155 additions and 0 deletions
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4
tools/testing/selftests/pidfd/pidfd.h
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@ -131,6 +131,10 @@
#define PIDFD_INFO_EXIT (1UL << 3) /* Always returned if available, even if not requested */
#endif
#ifndef PIDFD_THREAD
#define PIDFD_THREAD O_EXCL
#endif
struct pidfd_info {
__u64 mask;
__u64 cgroupid;

151
tools/testing/selftests/pidfd/pidfd_info_test.c
View File

@ -218,4 +218,155 @@ TEST_F(pidfd_info, success_reaped_poll)
ASSERT_EQ(WTERMSIG(info.exit_code), SIGKILL);
}
static void *pidfd_info_pause_thread(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;
close(ipc_socket);
/* Sleep untill we're killed. */
pause();
return NULL;
}
TEST_F(pidfd_info, thread_group)
{
pid_t pid_leader, pid_thread;
pthread_t thread;
int nevents, pidfd_leader, pidfd_thread, pidfd_leader_thread, ret;
int ipc_sockets[2];
struct pollfd fds = {};
struct pidfd_info info = {
.mask = PIDFD_INFO_CGROUPID | PIDFD_INFO_EXIT,
}, info2;
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_pause_thread, &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));
EXPECT_EQ(close(ipc_sockets[0]), 0);
/* Opening a thread as a thread-group leader must fail. */
pidfd_thread = sys_pidfd_open(pid_thread, 0);
ASSERT_LT(pidfd_thread, 0);
/* Opening a thread as a PIDFD_THREAD must succeed. */
pidfd_thread = sys_pidfd_open(pid_thread, PIDFD_THREAD);
ASSERT_GE(pidfd_thread, 0);
/*
* Opening a PIDFD_THREAD aka thread-specific pidfd based on a
* thread-group leader must succeed.
*/
pidfd_leader_thread = sys_pidfd_open(pid_leader, PIDFD_THREAD);
ASSERT_GE(pidfd_leader_thread, 0);
/*
* Note that pidfd_leader is a thread-group pidfd, so polling on it
* would only notify us once all thread in the thread-group have
* exited. So we can't poll before we have taken down the whole
* thread-group.
*/
/* Get PIDFD_GET_INFO using the thread-group leader pidfd. */
ASSERT_EQ(ioctl(pidfd_leader, PIDFD_GET_INFO, &info), 0);
ASSERT_TRUE(!!(info.mask & PIDFD_INFO_CREDS));
/* Process has exited but not been reaped, so no PIDFD_INFO_EXIT information yet. */
ASSERT_FALSE(!!(info.mask & PIDFD_INFO_EXIT));
ASSERT_EQ(info.pid, pid_leader);
/*
* Now retrieve the same info using the thread specific pidfd
* for the thread-group leader.
*/
info2.mask = PIDFD_INFO_CGROUPID | PIDFD_INFO_EXIT;
ASSERT_EQ(ioctl(pidfd_leader_thread, PIDFD_GET_INFO, &info2), 0);
ASSERT_TRUE(!!(info2.mask & PIDFD_INFO_CREDS));
/* Process has exited but not been reaped, so no PIDFD_INFO_EXIT information yet. */
ASSERT_FALSE(!!(info2.mask & PIDFD_INFO_EXIT));
ASSERT_EQ(info2.pid, pid_leader);
/* Now try the thread-specific pidfd. */
ASSERT_EQ(ioctl(pidfd_thread, PIDFD_GET_INFO, &info), 0);
ASSERT_TRUE(!!(info.mask & PIDFD_INFO_CREDS));
/* The thread hasn't exited, so no PIDFD_INFO_EXIT information yet. */
ASSERT_FALSE(!!(info.mask & PIDFD_INFO_EXIT));
ASSERT_EQ(info.pid, pid_thread);
/*
* Take down the whole thread-group. The thread-group leader
* exited successfully but the thread will now be SIGKILLed.
* This must be reflected in the recorded exit information.
*/
EXPECT_EQ(sys_pidfd_send_signal(pidfd_leader, SIGKILL, NULL, 0), 0);
EXPECT_EQ(sys_waitid(P_PIDFD, pidfd_leader, NULL, WEXITED), 0);
fds.events = POLLIN;
fds.fd = pidfd_leader;
nevents = poll(&fds, 1, -1);
ASSERT_EQ(nevents, 1);
ASSERT_TRUE(!!(fds.revents & POLLIN));
/* The thread-group leader has been reaped. */
ASSERT_TRUE(!!(fds.revents & POLLHUP));
/*
* Retrieve exit information for the thread-group leader via the
* thread-group leader pidfd.
*/
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));
/* The thread-group leader exited successfully. Only the specific thread was SIGKILLed. */
ASSERT_TRUE(WIFEXITED(info.exit_code));
ASSERT_EQ(WEXITSTATUS(info.exit_code), 0);
/*
* Retrieve exit information for the thread-group leader via the
* thread-specific pidfd.
*/
info2.mask = PIDFD_INFO_CGROUPID | PIDFD_INFO_EXIT;
ASSERT_EQ(ioctl(pidfd_leader_thread, PIDFD_GET_INFO, &info2), 0);
ASSERT_FALSE(!!(info2.mask & PIDFD_INFO_CREDS));
ASSERT_TRUE(!!(info2.mask & PIDFD_INFO_EXIT));
/* The thread-group leader exited successfully. Only the specific thread was SIGKILLed. */
ASSERT_TRUE(WIFEXITED(info2.exit_code));
ASSERT_EQ(WEXITSTATUS(info2.exit_code), 0);
/* Retrieve exit information for the thread. */
info.mask = PIDFD_INFO_CGROUPID | PIDFD_INFO_EXIT;
ASSERT_EQ(ioctl(pidfd_thread, PIDFD_GET_INFO, &info), 0);
ASSERT_FALSE(!!(info.mask & PIDFD_INFO_CREDS));
ASSERT_TRUE(!!(info.mask & PIDFD_INFO_EXIT));
/* The thread got SIGKILLed. */
ASSERT_TRUE(WIFSIGNALED(info.exit_code));
ASSERT_EQ(WTERMSIG(info.exit_code), SIGKILL);
EXPECT_EQ(close(pidfd_leader), 0);
EXPECT_EQ(close(pidfd_thread), 0);
}
TEST_HARNESS_MAIN