Add tests for the new CLONE_AUTOREAP clone3() flag: - autoreap_requires_pidfd: CLONE_AUTOREAP without CLONE_PIDFD fails - autoreap_rejects_exit_signal: CLONE_AUTOREAP with non-zero exit_signal fails - autoreap_rejects_thread: CLONE_AUTOREAP with CLONE_THREAD fails - autoreap_basic: child exits, pidfd poll works, PIDFD_GET_INFO returns correct exit code, waitpid() returns -ECHILD - autoreap_signaled: child killed by signal, exit info correct via pidfd - autoreap_reparent: autoreap grandchild reparented to subreaper still auto-reaps - autoreap_multithreaded: autoreap process with sub-threads auto-reaps after last thread exits - autoreap_no_inherit: grandchild forked without CLONE_AUTOREAP becomes a regular zombie Signed-off-by: Christian Brauner --- tools/testing/selftests/pidfd/.gitignore | 1 + tools/testing/selftests/pidfd/Makefile | 2 +- .../testing/selftests/pidfd/pidfd_autoreap_test.c | 489 +++++++++++++++++++++ 3 files changed, 491 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/pidfd/.gitignore b/tools/testing/selftests/pidfd/.gitignore index 144e7ff65d6a..4cd8ec7fd349 100644 --- a/tools/testing/selftests/pidfd/.gitignore +++ b/tools/testing/selftests/pidfd/.gitignore @@ -12,3 +12,4 @@ pidfd_info_test pidfd_exec_helper pidfd_xattr_test pidfd_setattr_test +pidfd_autoreap_test diff --git a/tools/testing/selftests/pidfd/Makefile b/tools/testing/selftests/pidfd/Makefile index 764a8f9ecefa..4211f91e9af8 100644 --- a/tools/testing/selftests/pidfd/Makefile +++ b/tools/testing/selftests/pidfd/Makefile @@ -4,7 +4,7 @@ CFLAGS += -g $(KHDR_INCLUDES) $(TOOLS_INCLUDES) -pthread -Wall 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 \ - pidfd_xattr_test pidfd_setattr_test + pidfd_xattr_test pidfd_setattr_test pidfd_autoreap_test TEST_GEN_PROGS_EXTENDED := pidfd_exec_helper diff --git a/tools/testing/selftests/pidfd/pidfd_autoreap_test.c b/tools/testing/selftests/pidfd/pidfd_autoreap_test.c new file mode 100644 index 000000000000..3c0c45359473 --- /dev/null +++ b/tools/testing/selftests/pidfd/pidfd_autoreap_test.c @@ -0,0 +1,489 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (c) 2026 Christian Brauner + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "pidfd.h" +#include "kselftest_harness.h" + +#ifndef CLONE_AUTOREAP +#define CLONE_AUTOREAP 0x400000000ULL +#endif + +static pid_t create_autoreap_child(int *pidfd) +{ + struct __clone_args args = { + .flags = CLONE_PIDFD | CLONE_AUTOREAP, + .exit_signal = 0, + .pidfd = ptr_to_u64(pidfd), + }; + + return sys_clone3(&args, sizeof(args)); +} + +/* + * Test that CLONE_AUTOREAP works without CLONE_PIDFD (fire-and-forget). + */ +TEST(autoreap_without_pidfd) +{ + struct __clone_args args = { + .flags = CLONE_AUTOREAP, + .exit_signal = 0, + }; + pid_t pid; + int ret; + + pid = sys_clone3(&args, sizeof(args)); + if (pid < 0 && errno == EINVAL) + SKIP(return, "CLONE_AUTOREAP not supported"); + ASSERT_GE(pid, 0); + + if (pid == 0) + _exit(0); + + /* + * Give the child a moment to exit and be autoreaped. + * Then verify no zombie remains. + */ + usleep(200000); + ret = waitpid(pid, NULL, WNOHANG); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, ECHILD); +} + +/* + * Test that CLONE_AUTOREAP with a non-zero exit_signal fails. + */ +TEST(autoreap_rejects_exit_signal) +{ + struct __clone_args args = { + .flags = CLONE_PIDFD | CLONE_AUTOREAP, + .exit_signal = SIGCHLD, + }; + int pidfd = -1; + pid_t pid; + + args.pidfd = ptr_to_u64(&pidfd); + + pid = sys_clone3(&args, sizeof(args)); + ASSERT_EQ(pid, -1); + ASSERT_EQ(errno, EINVAL); +} + +/* + * Test that CLONE_AUTOREAP with CLONE_THREAD fails. + */ +TEST(autoreap_rejects_thread) +{ + struct __clone_args args = { + .flags = CLONE_PIDFD | CLONE_AUTOREAP | + CLONE_THREAD | CLONE_SIGHAND | + CLONE_VM, + .exit_signal = 0, + }; + int pidfd = -1; + pid_t pid; + + args.pidfd = ptr_to_u64(&pidfd); + + pid = sys_clone3(&args, sizeof(args)); + ASSERT_EQ(pid, -1); + ASSERT_EQ(errno, EINVAL); +} + +/* + * Basic test: create an autoreap child, let it exit, verify: + * - pidfd becomes readable (poll returns POLLIN) + * - PIDFD_GET_INFO returns the correct exit code + * - waitpid() returns -1/ECHILD (no zombie) + */ +TEST(autoreap_basic) +{ + struct pidfd_info info = { .mask = PIDFD_INFO_EXIT }; + int pidfd = -1, ret; + struct pollfd pfd; + pid_t pid; + + pid = create_autoreap_child(&pidfd); + if (pid < 0 && errno == EINVAL) + SKIP(return, "CLONE_AUTOREAP not supported"); + ASSERT_GE(pid, 0); + + if (pid == 0) + _exit(42); + + ASSERT_GE(pidfd, 0); + + /* Wait for the child to exit via pidfd poll. */ + pfd.fd = pidfd; + pfd.events = POLLIN; + ret = poll(&pfd, 1, 5000); + ASSERT_EQ(ret, 1); + ASSERT_TRUE(pfd.revents & POLLIN); + + /* Verify exit info via PIDFD_GET_INFO. */ + ret = ioctl(pidfd, PIDFD_GET_INFO, &info); + ASSERT_EQ(ret, 0); + ASSERT_TRUE(info.mask & PIDFD_INFO_EXIT); + /* + * exit_code is in waitpid format: for _exit(42), + * WIFEXITED is true and WEXITSTATUS is 42. + */ + ASSERT_TRUE(WIFEXITED(info.exit_code)); + ASSERT_EQ(WEXITSTATUS(info.exit_code), 42); + + /* Verify no zombie: waitpid should fail with ECHILD. */ + ret = waitpid(pid, NULL, WNOHANG); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, ECHILD); + + close(pidfd); +} + +/* + * Test that an autoreap child killed by a signal reports + * the correct exit info. + */ +TEST(autoreap_signaled) +{ + struct pidfd_info info = { .mask = PIDFD_INFO_EXIT }; + int pidfd = -1, ret; + struct pollfd pfd; + pid_t pid; + + pid = create_autoreap_child(&pidfd); + if (pid < 0 && errno == EINVAL) + SKIP(return, "CLONE_AUTOREAP not supported"); + ASSERT_GE(pid, 0); + + if (pid == 0) { + pause(); + _exit(1); + } + + ASSERT_GE(pidfd, 0); + + /* Kill the child. */ + ret = sys_pidfd_send_signal(pidfd, SIGKILL, NULL, 0); + ASSERT_EQ(ret, 0); + + /* Wait for exit via pidfd. */ + pfd.fd = pidfd; + pfd.events = POLLIN; + ret = poll(&pfd, 1, 5000); + ASSERT_EQ(ret, 1); + ASSERT_TRUE(pfd.revents & POLLIN); + + /* Verify signal info. */ + ret = ioctl(pidfd, PIDFD_GET_INFO, &info); + ASSERT_EQ(ret, 0); + ASSERT_TRUE(info.mask & PIDFD_INFO_EXIT); + ASSERT_TRUE(WIFSIGNALED(info.exit_code)); + ASSERT_EQ(WTERMSIG(info.exit_code), SIGKILL); + + /* No zombie. */ + ret = waitpid(pid, NULL, WNOHANG); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, ECHILD); + + close(pidfd); +} + +/* + * Test autoreap survives reparenting: middle process creates an + * autoreap grandchild, then exits. The grandchild gets reparented + * to us (the grandparent, which is a subreaper). When the grandchild + * exits, it should still be autoreaped - no zombie under us. + */ +TEST(autoreap_reparent) +{ + int ipc_sockets[2], ret; + int pidfd = -1; + struct pollfd pfd; + pid_t mid_pid, grandchild_pid; + char buf[32] = {}; + + /* Make ourselves a subreaper so reparented children come to us. */ + ret = prctl(PR_SET_CHILD_SUBREAPER, 1); + ASSERT_EQ(ret, 0); + + ret = socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets); + ASSERT_EQ(ret, 0); + + mid_pid = fork(); + ASSERT_GE(mid_pid, 0); + + if (mid_pid == 0) { + /* Middle child: create an autoreap grandchild. */ + int gc_pidfd = -1; + + close(ipc_sockets[0]); + + grandchild_pid = create_autoreap_child(&gc_pidfd); + if (grandchild_pid < 0) { + write_nointr(ipc_sockets[1], "E", 1); + close(ipc_sockets[1]); + _exit(1); + } + + if (grandchild_pid == 0) { + /* Grandchild: wait for signal to exit. */ + close(ipc_sockets[1]); + if (gc_pidfd >= 0) + close(gc_pidfd); + pause(); + _exit(0); + } + + /* Send grandchild PID to grandparent. */ + snprintf(buf, sizeof(buf), "%d", grandchild_pid); + write_nointr(ipc_sockets[1], buf, strlen(buf)); + close(ipc_sockets[1]); + if (gc_pidfd >= 0) + close(gc_pidfd); + + /* Middle child exits, grandchild gets reparented. */ + _exit(0); + } + + close(ipc_sockets[1]); + + /* Read grandchild's PID. */ + ret = read_nointr(ipc_sockets[0], buf, sizeof(buf) - 1); + close(ipc_sockets[0]); + ASSERT_GT(ret, 0); + + if (buf[0] == 'E') { + waitpid(mid_pid, NULL, 0); + prctl(PR_SET_CHILD_SUBREAPER, 0); + SKIP(return, "CLONE_AUTOREAP not supported"); + } + + grandchild_pid = atoi(buf); + ASSERT_GT(grandchild_pid, 0); + + /* Wait for the middle child to exit. */ + ret = waitpid(mid_pid, NULL, 0); + ASSERT_EQ(ret, mid_pid); + + /* + * Now the grandchild is reparented to us (subreaper). + * Open a pidfd for the grandchild and kill it. + */ + pidfd = sys_pidfd_open(grandchild_pid, 0); + ASSERT_GE(pidfd, 0); + + ret = sys_pidfd_send_signal(pidfd, SIGKILL, NULL, 0); + ASSERT_EQ(ret, 0); + + /* Wait for it to exit via pidfd poll. */ + pfd.fd = pidfd; + pfd.events = POLLIN; + ret = poll(&pfd, 1, 5000); + ASSERT_EQ(ret, 1); + ASSERT_TRUE(pfd.revents & POLLIN); + + /* + * The grandchild should have been autoreaped even though + * we (the new parent) haven't set SA_NOCLDWAIT. + * waitpid should return -1/ECHILD. + */ + ret = waitpid(grandchild_pid, NULL, WNOHANG); + EXPECT_EQ(ret, -1); + EXPECT_EQ(errno, ECHILD); + + close(pidfd); + + /* Clean up subreaper status. */ + prctl(PR_SET_CHILD_SUBREAPER, 0); +} + +static int thread_sock_fd; + +static void *thread_func(void *arg) +{ + /* Signal parent we're running. */ + write_nointr(thread_sock_fd, "1", 1); + + /* Give main thread time to call _exit() first. */ + usleep(200000); + + return NULL; +} + +/* + * Test that an autoreap child with multiple threads is properly + * autoreaped only after all threads have exited. + */ +TEST(autoreap_multithreaded) +{ + struct pidfd_info info = { .mask = PIDFD_INFO_EXIT }; + int ipc_sockets[2], ret; + int pidfd = -1; + struct pollfd pfd; + pid_t pid; + char c; + + ret = socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets); + ASSERT_EQ(ret, 0); + + pid = create_autoreap_child(&pidfd); + if (pid < 0 && errno == EINVAL) { + close(ipc_sockets[0]); + close(ipc_sockets[1]); + SKIP(return, "CLONE_AUTOREAP not supported"); + } + ASSERT_GE(pid, 0); + + if (pid == 0) { + pthread_t thread; + + close(ipc_sockets[0]); + + /* + * Create a sub-thread that outlives the main thread. + * The thread signals readiness, then sleeps. + * The main thread waits briefly, then calls _exit(). + */ + thread_sock_fd = ipc_sockets[1]; + pthread_create(&thread, NULL, thread_func, NULL); + pthread_detach(thread); + + /* Wait for thread to be running. */ + usleep(100000); + + /* Main thread exits; sub-thread is still alive. */ + _exit(99); + } + + close(ipc_sockets[1]); + + /* Wait for the sub-thread to signal readiness. */ + ret = read_nointr(ipc_sockets[0], &c, 1); + close(ipc_sockets[0]); + ASSERT_EQ(ret, 1); + + /* Wait for the process to fully exit via pidfd poll. */ + pfd.fd = pidfd; + pfd.events = POLLIN; + ret = poll(&pfd, 1, 5000); + ASSERT_EQ(ret, 1); + ASSERT_TRUE(pfd.revents & POLLIN); + + /* Verify exit info. */ + ret = ioctl(pidfd, PIDFD_GET_INFO, &info); + ASSERT_EQ(ret, 0); + ASSERT_TRUE(info.mask & PIDFD_INFO_EXIT); + ASSERT_TRUE(WIFEXITED(info.exit_code)); + ASSERT_EQ(WEXITSTATUS(info.exit_code), 99); + + /* No zombie. */ + ret = waitpid(pid, NULL, WNOHANG); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, ECHILD); + + close(pidfd); +} + +/* + * Test that autoreap is NOT inherited by grandchildren. + */ +TEST(autoreap_no_inherit) +{ + int ipc_sockets[2], ret; + int pidfd = -1; + pid_t pid; + char buf[2] = {}; + struct pollfd pfd; + + ret = socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets); + ASSERT_EQ(ret, 0); + + pid = create_autoreap_child(&pidfd); + if (pid < 0 && errno == EINVAL) { + close(ipc_sockets[0]); + close(ipc_sockets[1]); + SKIP(return, "CLONE_AUTOREAP not supported"); + } + ASSERT_GE(pid, 0); + + if (pid == 0) { + pid_t gc; + int status; + + close(ipc_sockets[0]); + + /* Autoreap child forks a grandchild (without autoreap). */ + gc = fork(); + if (gc < 0) { + write_nointr(ipc_sockets[1], "E", 1); + _exit(1); + } + if (gc == 0) { + /* Grandchild: exit immediately. */ + close(ipc_sockets[1]); + _exit(77); + } + + /* + * The grandchild should become a regular zombie + * since it was NOT created with CLONE_AUTOREAP. + * Wait for it to verify. + */ + ret = waitpid(gc, &status, 0); + if (ret == gc && WIFEXITED(status) && + WEXITSTATUS(status) == 77) { + write_nointr(ipc_sockets[1], "P", 1); + } else { + write_nointr(ipc_sockets[1], "F", 1); + } + close(ipc_sockets[1]); + _exit(0); + } + + close(ipc_sockets[1]); + + ret = read_nointr(ipc_sockets[0], buf, 1); + close(ipc_sockets[0]); + ASSERT_EQ(ret, 1); + + /* + * 'P' means the autoreap child was able to waitpid() its + * grandchild (correct - grandchild should be a normal zombie, + * not autoreaped). + */ + ASSERT_EQ(buf[0], 'P'); + + /* Wait for the autoreap child to exit. */ + pfd.fd = pidfd; + pfd.events = POLLIN; + ret = poll(&pfd, 1, 5000); + ASSERT_EQ(ret, 1); + + /* Autoreap child itself should be autoreaped. */ + ret = waitpid(pid, NULL, WNOHANG); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, ECHILD); + + close(pidfd); +} + +TEST_HARNESS_MAIN -- 2.47.3