Add tests for CLONE_PIDFD_AUTOKILL: - autokill_basic: Verify closing the clone3 pidfd kills the child. - autokill_requires_pidfd: Verify AUTOKILL without CLONE_PIDFD fails. - autokill_requires_autoreap: Verify AUTOKILL without CLONE_AUTOREAP fails. - autokill_rejects_thread: Verify AUTOKILL with CLONE_THREAD fails. - autokill_pidfd_open_no_effect: Verify only the clone3 pidfd triggers autokill, not pidfd_open(). - autokill_requires_cap_sys_admin: Verify AUTOKILL without CLONE_NNP fails with -EPERM for an unprivileged caller. - autokill_without_nnp_with_cap: Verify AUTOKILL without CLONE_NNP succeeds with CAP_SYS_ADMIN. Signed-off-by: Christian Brauner --- .../testing/selftests/pidfd/pidfd_autoreap_test.c | 278 +++++++++++++++++++++ 1 file changed, 278 insertions(+) diff --git a/tools/testing/selftests/pidfd/pidfd_autoreap_test.c b/tools/testing/selftests/pidfd/pidfd_autoreap_test.c index 5fb11230fb07..36adee6c424e 100644 --- a/tools/testing/selftests/pidfd/pidfd_autoreap_test.c +++ b/tools/testing/selftests/pidfd/pidfd_autoreap_test.c @@ -26,10 +26,37 @@ #define CLONE_AUTOREAP 0x400000000ULL #endif +#ifndef CLONE_PIDFD_AUTOKILL +#define CLONE_PIDFD_AUTOKILL 0x800000000ULL +#endif + #ifndef CLONE_NNP #define CLONE_NNP 0x1000000000ULL #endif +#ifndef _LINUX_CAPABILITY_VERSION_3 +#define _LINUX_CAPABILITY_VERSION_3 0x20080522 +#endif + +struct cap_header { + __u32 version; + int pid; +}; + +struct cap_data { + __u32 effective; + __u32 permitted; + __u32 inheritable; +}; + +static int drop_all_caps(void) +{ + struct cap_header hdr = { .version = _LINUX_CAPABILITY_VERSION_3 }; + struct cap_data data[2] = {}; + + return syscall(__NR_capset, &hdr, data); +} + static pid_t create_autoreap_child(int *pidfd) { struct __clone_args args = { @@ -619,4 +646,255 @@ TEST(autoreap_no_new_privs_unset) close(pidfd); } +/* + * Helper: create a child with CLONE_PIDFD | CLONE_PIDFD_AUTOKILL | CLONE_AUTOREAP | CLONE_NNP. + */ +static pid_t create_autokill_child(int *pidfd) +{ + struct __clone_args args = { + .flags = CLONE_PIDFD | CLONE_PIDFD_AUTOKILL | + CLONE_AUTOREAP | CLONE_NNP, + .exit_signal = 0, + .pidfd = ptr_to_u64(pidfd), + }; + + return sys_clone3(&args, sizeof(args)); +} + +/* + * Basic autokill test: child blocks in pause(), parent closes the + * clone3 pidfd, child should be killed and autoreaped. + */ +TEST(autokill_basic) +{ + int pidfd = -1, pollfd_fd = -1, ret; + struct pollfd pfd; + pid_t pid; + + pid = create_autokill_child(&pidfd); + if (pid < 0 && errno == EINVAL) + SKIP(return, "CLONE_PIDFD_AUTOKILL not supported"); + ASSERT_GE(pid, 0); + + if (pid == 0) { + pause(); + _exit(1); + } + + ASSERT_GE(pidfd, 0); + + /* + * Open a second pidfd via pidfd_open() so we can observe the + * child's death after closing the clone3 pidfd. + */ + pollfd_fd = sys_pidfd_open(pid, 0); + ASSERT_GE(pollfd_fd, 0); + + /* Close the clone3 pidfd — this should trigger autokill. */ + close(pidfd); + + /* Wait for the child to die via the pidfd_open'd fd. */ + pfd.fd = pollfd_fd; + pfd.events = POLLIN; + ret = poll(&pfd, 1, 5000); + ASSERT_EQ(ret, 1); + ASSERT_TRUE(pfd.revents & POLLIN); + + /* Child should be autoreaped — no zombie. */ + usleep(100000); + ret = waitpid(pid, NULL, WNOHANG); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, ECHILD); + + close(pollfd_fd); +} + +/* + * CLONE_PIDFD_AUTOKILL without CLONE_PIDFD must fail with EINVAL. + */ +TEST(autokill_requires_pidfd) +{ + struct __clone_args args = { + .flags = CLONE_PIDFD_AUTOKILL | CLONE_AUTOREAP, + .exit_signal = 0, + }; + pid_t pid; + + pid = sys_clone3(&args, sizeof(args)); + ASSERT_EQ(pid, -1); + ASSERT_EQ(errno, EINVAL); +} + +/* + * CLONE_PIDFD_AUTOKILL without CLONE_AUTOREAP must fail with EINVAL. + */ +TEST(autokill_requires_autoreap) +{ + int pidfd = -1; + struct __clone_args args = { + .flags = CLONE_PIDFD | CLONE_PIDFD_AUTOKILL, + .exit_signal = 0, + .pidfd = ptr_to_u64(&pidfd), + }; + pid_t pid; + + pid = sys_clone3(&args, sizeof(args)); + ASSERT_EQ(pid, -1); + ASSERT_EQ(errno, EINVAL); +} + +/* + * CLONE_PIDFD_AUTOKILL with CLONE_THREAD must fail with EINVAL. + */ +TEST(autokill_rejects_thread) +{ + int pidfd = -1; + struct __clone_args args = { + .flags = CLONE_PIDFD | CLONE_PIDFD_AUTOKILL | + CLONE_AUTOREAP | CLONE_THREAD | + CLONE_SIGHAND | CLONE_VM, + .exit_signal = 0, + .pidfd = ptr_to_u64(&pidfd), + }; + pid_t pid; + + pid = sys_clone3(&args, sizeof(args)); + ASSERT_EQ(pid, -1); + ASSERT_EQ(errno, EINVAL); +} + +/* + * Test that only the clone3 pidfd triggers autokill, not pidfd_open(). + * Close the pidfd_open'd fd first — child should survive. + * Then close the clone3 pidfd — child should be killed and autoreaped. + */ +TEST(autokill_pidfd_open_no_effect) +{ + int pidfd = -1, open_fd = -1, ret; + struct pollfd pfd; + pid_t pid; + + pid = create_autokill_child(&pidfd); + if (pid < 0 && errno == EINVAL) + SKIP(return, "CLONE_PIDFD_AUTOKILL not supported"); + ASSERT_GE(pid, 0); + + if (pid == 0) { + pause(); + _exit(1); + } + + ASSERT_GE(pidfd, 0); + + /* Open a second pidfd via pidfd_open(). */ + open_fd = sys_pidfd_open(pid, 0); + ASSERT_GE(open_fd, 0); + + /* + * Close the pidfd_open'd fd — child should survive because + * only the clone3 pidfd has autokill. + */ + close(open_fd); + usleep(200000); + + /* Verify child is still alive by polling the clone3 pidfd. */ + pfd.fd = pidfd; + pfd.events = POLLIN; + ret = poll(&pfd, 1, 0); + ASSERT_EQ(ret, 0) { + TH_LOG("Child died after closing pidfd_open fd — should still be alive"); + } + + /* Open another observation fd before triggering autokill. */ + open_fd = sys_pidfd_open(pid, 0); + ASSERT_GE(open_fd, 0); + + /* Now close the clone3 pidfd — this triggers autokill. */ + close(pidfd); + + pfd.fd = open_fd; + pfd.events = POLLIN; + ret = poll(&pfd, 1, 5000); + ASSERT_EQ(ret, 1); + ASSERT_TRUE(pfd.revents & POLLIN); + + /* Child should be autoreaped — no zombie. */ + usleep(100000); + ret = waitpid(pid, NULL, WNOHANG); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, ECHILD); + + close(open_fd); +} + +/* + * Test that CLONE_PIDFD_AUTOKILL without CLONE_NNP fails with EPERM + * for an unprivileged caller. + */ +TEST(autokill_requires_cap_sys_admin) +{ + int pidfd = -1, ret; + struct __clone_args args = { + .flags = CLONE_PIDFD | CLONE_PIDFD_AUTOKILL | + CLONE_AUTOREAP, + .exit_signal = 0, + .pidfd = ptr_to_u64(&pidfd), + }; + pid_t pid; + + /* Drop all capabilities so we lack CAP_SYS_ADMIN. */ + ret = drop_all_caps(); + ASSERT_EQ(ret, 0); + + pid = sys_clone3(&args, sizeof(args)); + ASSERT_EQ(pid, -1); + ASSERT_EQ(errno, EPERM); +} + +/* + * Test that CLONE_PIDFD_AUTOKILL without CLONE_NNP succeeds with + * CAP_SYS_ADMIN. + */ +TEST(autokill_without_nnp_with_cap) +{ + struct __clone_args args = { + .flags = CLONE_PIDFD | CLONE_PIDFD_AUTOKILL | + CLONE_AUTOREAP, + .exit_signal = 0, + }; + struct pidfd_info info = { .mask = PIDFD_INFO_EXIT }; + int pidfd = -1, ret; + struct pollfd pfd; + pid_t pid; + + if (geteuid() != 0) + SKIP(return, "Need root/CAP_SYS_ADMIN"); + + args.pidfd = ptr_to_u64(&pidfd); + + pid = sys_clone3(&args, sizeof(args)); + if (pid < 0 && errno == EINVAL) + SKIP(return, "CLONE_PIDFD_AUTOKILL not supported"); + ASSERT_GE(pid, 0); + + if (pid == 0) + _exit(0); + + ASSERT_GE(pidfd, 0); + + /* Wait for child to exit. */ + pfd.fd = pidfd; + pfd.events = POLLIN; + ret = poll(&pfd, 1, 5000); + ASSERT_EQ(ret, 1); + + 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), 0); + + close(pidfd); +} + TEST_HARNESS_MAIN -- 2.47.3