diff options
Diffstat (limited to 'tools/testing/selftests/landlock/tsync_test.c')
| -rw-r--r-- | tools/testing/selftests/landlock/tsync_test.c | 327 |
1 files changed, 327 insertions, 0 deletions
diff --git a/tools/testing/selftests/landlock/tsync_test.c b/tools/testing/selftests/landlock/tsync_test.c new file mode 100644 index 000000000000..9cf1491bbaaf --- /dev/null +++ b/tools/testing/selftests/landlock/tsync_test.c @@ -0,0 +1,327 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Landlock tests - Enforcing the same restrictions across multiple threads + * + * Copyright © 2025 Günther Noack <gnoack3000@gmail.com> + */ + +#define _GNU_SOURCE +#include <linux/landlock.h> +#include <pthread.h> +#include <signal.h> +#include <sys/prctl.h> + +#include "common.h" + +/* create_ruleset - Create a simple ruleset FD common to all tests */ +static int create_ruleset(struct __test_metadata *const _metadata) +{ + struct landlock_ruleset_attr ruleset_attr = { + .handled_access_fs = (LANDLOCK_ACCESS_FS_WRITE_FILE | + LANDLOCK_ACCESS_FS_TRUNCATE), + }; + const int ruleset_fd = + landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); + + ASSERT_LE(0, ruleset_fd) + { + TH_LOG("landlock_create_ruleset: %s", strerror(errno)); + } + return ruleset_fd; +} + +TEST(single_threaded_success) +{ + const int ruleset_fd = create_ruleset(_metadata); + + disable_caps(_metadata); + + ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)); + ASSERT_EQ(0, landlock_restrict_self(ruleset_fd, + LANDLOCK_RESTRICT_SELF_TSYNC)); + + EXPECT_EQ(0, close(ruleset_fd)); +} + +static void store_no_new_privs(void *data) +{ + bool *nnp = data; + + if (!nnp) + return; + *nnp = prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0); +} + +static void *idle(void *data) +{ + pthread_cleanup_push(store_no_new_privs, data); + + while (true) + sleep(1); + + pthread_cleanup_pop(1); +} + +TEST(multi_threaded_success) +{ + pthread_t t1, t2; + bool no_new_privs1, no_new_privs2; + const int ruleset_fd = create_ruleset(_metadata); + + disable_caps(_metadata); + + ASSERT_EQ(0, pthread_create(&t1, NULL, idle, &no_new_privs1)); + ASSERT_EQ(0, pthread_create(&t2, NULL, idle, &no_new_privs2)); + + ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)); + + EXPECT_EQ(0, landlock_restrict_self(ruleset_fd, + LANDLOCK_RESTRICT_SELF_TSYNC)); + + ASSERT_EQ(0, pthread_cancel(t1)); + ASSERT_EQ(0, pthread_cancel(t2)); + ASSERT_EQ(0, pthread_join(t1, NULL)); + ASSERT_EQ(0, pthread_join(t2, NULL)); + + /* The no_new_privs flag was implicitly enabled on all threads. */ + EXPECT_TRUE(no_new_privs1); + EXPECT_TRUE(no_new_privs2); + + EXPECT_EQ(0, close(ruleset_fd)); +} + +TEST(multi_threaded_success_despite_diverging_domains) +{ + pthread_t t1, t2; + const int ruleset_fd = create_ruleset(_metadata); + + disable_caps(_metadata); + + ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)); + + ASSERT_EQ(0, pthread_create(&t1, NULL, idle, NULL)); + ASSERT_EQ(0, pthread_create(&t2, NULL, idle, NULL)); + + /* + * The main thread enforces a ruleset, + * thereby bringing the threads' Landlock domains out of sync. + */ + EXPECT_EQ(0, landlock_restrict_self(ruleset_fd, 0)); + + /* Still, TSYNC succeeds, bringing the threads in sync again. */ + EXPECT_EQ(0, landlock_restrict_self(ruleset_fd, + LANDLOCK_RESTRICT_SELF_TSYNC)); + + ASSERT_EQ(0, pthread_cancel(t1)); + ASSERT_EQ(0, pthread_cancel(t2)); + ASSERT_EQ(0, pthread_join(t1, NULL)); + ASSERT_EQ(0, pthread_join(t2, NULL)); + EXPECT_EQ(0, close(ruleset_fd)); +} + +struct thread_restrict_data { + pthread_t t; + int ruleset_fd; + int result; +}; + +static void *thread_restrict(void *data) +{ + struct thread_restrict_data *d = data; + + d->result = landlock_restrict_self(d->ruleset_fd, + LANDLOCK_RESTRICT_SELF_TSYNC); + return NULL; +} + +TEST(competing_enablement) +{ + const int ruleset_fd = create_ruleset(_metadata); + struct thread_restrict_data d[] = { + { .ruleset_fd = ruleset_fd }, + { .ruleset_fd = ruleset_fd }, + }; + + disable_caps(_metadata); + + ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)); + ASSERT_EQ(0, pthread_create(&d[0].t, NULL, thread_restrict, &d[0])); + ASSERT_EQ(0, pthread_create(&d[1].t, NULL, thread_restrict, &d[1])); + + /* Wait for threads to finish. */ + ASSERT_EQ(0, pthread_join(d[0].t, NULL)); + ASSERT_EQ(0, pthread_join(d[1].t, NULL)); + + /* Expect that both succeeded. */ + EXPECT_EQ(0, d[0].result); + EXPECT_EQ(0, d[1].result); + + EXPECT_EQ(0, close(ruleset_fd)); +} + +static void signal_nop_handler(int sig) +{ +} + +struct signaler_data { + pthread_t target; + volatile bool stop; +}; + +static void *signaler_thread(void *data) +{ + struct signaler_data *sd = data; + + while (!sd->stop) + pthread_kill(sd->target, SIGUSR1); + + return NULL; +} + +/* + * Number of idle sibling threads. This must be large enough that even on + * machines with many cores, the sibling threads cannot all complete their + * credential preparation in a single parallel wave, otherwise the signaler + * thread has no window to interrupt wait_for_completion_interruptible(). + * 200 threads on a 64-core machine yields ~3 serialized waves, giving the + * tight signal loop enough time to land an interruption. + */ +#define NUM_IDLE_THREADS 200 + +/* + * Exercises the tsync interruption and cancellation paths in tsync.c. + * + * When a signal interrupts the calling thread while it waits for sibling + * threads to finish their credential preparation + * (wait_for_completion_interruptible in landlock_restrict_sibling_threads), + * the kernel sets ERESTARTNOINTR, cancels queued task works that have not + * started yet (cancel_tsync_works), then waits for the remaining works to + * finish. On the error return, syscalls.c aborts the prepared credentials. + * The kernel automatically restarts the syscall, so userspace sees success. + */ +TEST(tsync_interrupt) +{ + size_t i; + pthread_t threads[NUM_IDLE_THREADS]; + pthread_t signaler; + struct signaler_data sd; + struct sigaction sa = {}; + const int ruleset_fd = create_ruleset(_metadata); + + disable_caps(_metadata); + + /* Install a no-op SIGUSR1 handler so the signal does not kill us. */ + sa.sa_handler = signal_nop_handler; + sigemptyset(&sa.sa_mask); + ASSERT_EQ(0, sigaction(SIGUSR1, &sa, NULL)); + + ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)); + + for (i = 0; i < NUM_IDLE_THREADS; i++) + ASSERT_EQ(0, pthread_create(&threads[i], NULL, idle, NULL)); + + /* + * Start a signaler thread that continuously sends SIGUSR1 to the + * calling thread. This maximizes the chance of interrupting + * wait_for_completion_interruptible() in the kernel's tsync path. + */ + sd.target = pthread_self(); + sd.stop = false; + ASSERT_EQ(0, pthread_create(&signaler, NULL, signaler_thread, &sd)); + + /* + * The syscall may be interrupted and transparently restarted by the + * kernel (ERESTARTNOINTR). From userspace, it should always succeed. + */ + EXPECT_EQ(0, landlock_restrict_self(ruleset_fd, + LANDLOCK_RESTRICT_SELF_TSYNC)); + + sd.stop = true; + ASSERT_EQ(0, pthread_join(signaler, NULL)); + + for (i = 0; i < NUM_IDLE_THREADS; i++) { + ASSERT_EQ(0, pthread_cancel(threads[i])); + ASSERT_EQ(0, pthread_join(threads[i], NULL)); + } + + EXPECT_EQ(0, close(ruleset_fd)); +} + +/* clang-format off */ +FIXTURE(tsync_without_ruleset) {}; +/* clang-format on */ + +FIXTURE_VARIANT(tsync_without_ruleset) +{ + const __u32 flags; + const int expected_errno; +}; + +/* clang-format off */ +FIXTURE_VARIANT_ADD(tsync_without_ruleset, tsync_only) { + /* clang-format on */ + .flags = LANDLOCK_RESTRICT_SELF_TSYNC, + .expected_errno = EBADF, +}; + +/* clang-format off */ +FIXTURE_VARIANT_ADD(tsync_without_ruleset, subdomains_off_same_exec_off) { + /* clang-format on */ + .flags = LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF | + LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF | + LANDLOCK_RESTRICT_SELF_TSYNC, + .expected_errno = EBADF, +}; + +/* clang-format off */ +FIXTURE_VARIANT_ADD(tsync_without_ruleset, subdomains_off_new_exec_on) { + /* clang-format on */ + .flags = LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF | + LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON | + LANDLOCK_RESTRICT_SELF_TSYNC, + .expected_errno = EBADF, +}; + +/* clang-format off */ +FIXTURE_VARIANT_ADD(tsync_without_ruleset, all_flags) { + /* clang-format on */ + .flags = LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF | + LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON | + LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF | + LANDLOCK_RESTRICT_SELF_TSYNC, + .expected_errno = EBADF, +}; + +/* clang-format off */ +FIXTURE_VARIANT_ADD(tsync_without_ruleset, subdomains_off) { + /* clang-format on */ + .flags = LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF | + LANDLOCK_RESTRICT_SELF_TSYNC, + .expected_errno = 0, +}; + +FIXTURE_SETUP(tsync_without_ruleset) +{ + disable_caps(_metadata); +} + +FIXTURE_TEARDOWN(tsync_without_ruleset) +{ +} + +TEST_F(tsync_without_ruleset, check) +{ + int ret; + + ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)); + + ret = landlock_restrict_self(-1, variant->flags); + if (variant->expected_errno) { + EXPECT_EQ(-1, ret); + EXPECT_EQ(variant->expected_errno, errno); + } else { + EXPECT_EQ(0, ret); + } +} + +TEST_HARNESS_MAIN |