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Sat, 19 Jul 2025 05:41:30 -0700 (PDT) From: Abhinav Saxena Date: Sat, 19 Jul 2025 06:41:26 -0600 Subject: [PATCH RFC 3/3] selftests/landlock: add cross-domain signal tests Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250719-landlock_abstractions-v1-3-2c4fd61f8973@gmail.com> References: <20250719-landlock_abstractions-v1-0-2c4fd61f8973@gmail.com> In-Reply-To: <20250719-landlock_abstractions-v1-0-2c4fd61f8973@gmail.com> To: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= , =?utf-8?q?G=C3=BCnther_Noack?= , Shuah Khan Cc: linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Abhinav Saxena X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1752928886; l=8891; i=xandfury@gmail.com; s=20250614; h=from:subject:message-id; bh=qO3QxPss+Ez6xIoDiDgrczAiXZ6fDnwcU1lYnvb8G1k=; b=+RxX9CTwk3BxNj4tjinZT8HNGYy8ZuS4HWwl/bwj7taZWoKrYxZdzmloBZhokScfRz/hwGmn8 W6fRce7JUCrB9lhK2Ze+fdsKfvUlKNfZRmkTizVkFGC9XobrXWBOZRA X-Developer-Key: i=xandfury@gmail.com; a=ed25519; pk=YN6w7WNet8skqvMWxhG5BlAmtd1SQmo8If6Mofh4k44= Add cross_domain_signal test using the new cross-domain variants to validate signal delivery between independent peer domains. This fills a gap in current test coverage which only exercises hierarchical domain relationships. The test creates a fork tree where both children call landlock_restrict_self() for the first time, ensuring their domain->parent pointers are NULL and creating true peer domains: coordinator (no domain) | +-- resource_proc (Domain X) /* owns the resource */ | +-- accessor_proc (Domain Y) /* tries to access */ Tests verify that kill(SIGUSR1) behaves correctly across all four domain combinations, with scoped accessors properly denied (-EPERM) when attempting cross-domain signal delivery. This establishes the resource-accessor test pattern for future scope types where Landlock restrictions apply only to the accessor side. Signed-off-by: Abhinav Saxena --- .../selftests/landlock/scoped_signal_test.c | 237 +++++++++++++++++= ++++ 1 file changed, 237 insertions(+) diff --git a/tools/testing/selftests/landlock/scoped_signal_test.c b/tools/= testing/selftests/landlock/scoped_signal_test.c index d8bf33417619..b52eaf1f3c0a 100644 --- a/tools/testing/selftests/landlock/scoped_signal_test.c +++ b/tools/testing/selftests/landlock/scoped_signal_test.c @@ -559,4 +559,241 @@ TEST_F(fown, sigurg_socket) _metadata->exit_code =3D KSFT_FAIL; } =20 +FIXTURE(cross_domain_scope) +{ + int coordinator_to_resource_pipe[2]; /* coordinator -> resource sync */ + int coordinator_to_accessor_pipe[2]; /* coordinator -> accessor sync */ + int result_pipe[2]; /* accessor -> coordinator result */ + pid_t resource_pid; /* Domain X process */ + pid_t accessor_pid; /* Domain Y process */ +}; + +/* Include the cross-domain variants */ +#include "scoped_cross_domain_variants.h" + +FIXTURE_SETUP(cross_domain_scope) +{ + drop_caps(_metadata); + /* Create communication channels */ + ASSERT_EQ(0, pipe2(self->coordinator_to_resource_pipe, O_CLOEXEC)); + ASSERT_EQ(0, pipe2(self->coordinator_to_accessor_pipe, O_CLOEXEC)); + ASSERT_EQ(0, pipe2(self->result_pipe, O_CLOEXEC)); + + signal_received =3D 0; /* Reset for each test */ + self->resource_pid =3D -1; + self->accessor_pid =3D -1; +} + +FIXTURE_TEARDOWN(cross_domain_scope) +{ + close(self->coordinator_to_resource_pipe[0]); + close(self->coordinator_to_resource_pipe[1]); + close(self->coordinator_to_accessor_pipe[0]); + close(self->coordinator_to_accessor_pipe[1]); + close(self->result_pipe[0]); + close(self->result_pipe[1]); +} + +static void cross_domain_signal_handler(int sig) +{ + if (sig =3D=3D SIGUSR1 || sig =3D=3D SIGURG) + signal_received =3D 1; + else if (sig =3D=3D SIGALRM) + signal_received =3D 2; /* Alarm timeout */ +} + +/* + * Maybe this should go into common.h or scoped_common.h so that + * we can perhaps test interactions b/w different types of sanboxes + */ +static void create_independent_domain(struct __test_metadata *_metadata, + enum sandbox_type domain_type, + const char *process_role) +{ + if (domain_type =3D=3D SCOPE_SANDBOX) { + /* + * This is the critical call - first landlock_restrict_self() + * ensures domain->parent =3D=3D NULL, creating true peer domains + */ + create_scoped_domain(_metadata, LANDLOCK_SCOPE_SIGNAL); + } +} + +TEST_F(cross_domain_scope, cross_domain_signal) +{ + enum sandbox_type resource_domain =3D variant->resource_domain; + enum sandbox_type accessor_domain =3D variant->accessor_domain; + + TH_LOG("Resource domain: %s", + resource_domain =3D=3D NO_SANDBOX ? "unrestricted" : "scoped"); + TH_LOG("Accessor domain: %s", + accessor_domain =3D=3D NO_SANDBOX ? "unrestricted" : "scoped"); + /* + * Fork tree: + * coordinator (no domain) + * =E2=94=9C=E2=94=80=E2=94=80 resource_proc (Domain X) + * =E2=94=94=E2=94=80=E2=94=80 accessor_proc (Domain Y) + */ + + /* =3D=3D=3D RESOURCE PROCESS (Domain X) =3D=3D=3D */ + self->resource_pid =3D fork(); + ASSERT_GE(self->resource_pid, 0); + + if (self->resource_pid =3D=3D 0) { + /* Close unused pipe ends */ + + /* Don't write to coordinator */ + close(self->coordinator_to_resource_pipe[1]); + /* Don't read accessor pipe */ + close(self->coordinator_to_accessor_pipe[0]); + /* Don't write accessor pipe */ + close(self->coordinator_to_accessor_pipe[1]); + close(self->result_pipe[0]); /* Don't read results */ + close(self->result_pipe[1]); /* Don't write results */ + + /* Create independent domain */ + create_independent_domain(_metadata, resource_domain, + "RESOURCE"); + + /* Install signal handler */ + struct sigaction sa =3D { + .sa_handler =3D cross_domain_signal_handler, + .sa_flags =3D SA_RESTART + }; + + sigemptyset(&sa.sa_mask); + ASSERT_EQ(0, sigaction(SIGUSR1, &sa, NULL)); + ASSERT_EQ(0, sigaction(SIGALRM, &sa, NULL)); + + /* Wait for coordinator signal to start */ + char sync_byte; + ssize_t ret =3D read(self->coordinator_to_resource_pipe[0], + &sync_byte, 1); + ASSERT_EQ(1, ret); + close(self->coordinator_to_resource_pipe[0]); + + /* Set timeout and wait for signal */ + alarm(3); + pause(); + + /* + * Exit based on what signal was received + * 0=3Dsuccess, 1=3Dtimeout/failure + */ + _exit(signal_received =3D=3D 1 ? 0 : 1); + } + + /* =3D=3D=3D ACCESSOR PROCESS (Domain Y) =3D=3D=3D */ + self->accessor_pid =3D fork(); + ASSERT_GE(self->accessor_pid, 0); + + if (self->accessor_pid =3D=3D 0) { + /* Close unused pipe ends */ + + /* Don't read resource pipe */ + close(self->coordinator_to_resource_pipe[0]); + /* Don't write resource pipe */ + close(self->coordinator_to_resource_pipe[1]); + /* Don't write to coordinator */ + close(self->coordinator_to_accessor_pipe[1]); + close(self->result_pipe[0]); /* Don't read results */ + + create_independent_domain(_metadata, accessor_domain, + "ACCESSOR"); + + /* Wait for coordinator to signal start */ + char sync_byte; + ssize_t ret =3D read(self->coordinator_to_accessor_pipe[0], + &sync_byte, 1); + ASSERT_EQ(1, ret); + close(self->coordinator_to_accessor_pipe[0]); + + /* 200ms delay to ensure resource is in pause() */ + usleep(200000); + + /* Attempt cross-domain signal - this is the core test */ + int kill_result =3D kill(self->resource_pid, SIGUSR1); + int kill_errno =3D errno; + + /* Send results back to coordinator */ + struct { + int result; + int error; + } test_result =3D { kill_result, kill_errno }; + + ret =3D write(self->result_pipe[1], &test_result, + sizeof(test_result)); + ASSERT_EQ(sizeof(test_result), ret); + close(self->result_pipe[1]); + + _exit(0); + } + + /* =3D=3D=3D COORDINATOR PROCESS (No domain) =3D=3D=3D */ + + /* Close unused pipe ends */ + close(self->coordinator_to_resource_pipe[0]); /* Don't read from resource= */ + close(self->coordinator_to_accessor_pipe[0]); /* Don't read from accessor= */ + close(self->result_pipe[1]); /* Don't write results */ + + /* Give processes time to set up domains */ + usleep(100000); /* 100ms */ + + /* Signal both processes to start the test */ + char go_signal =3D '1'; + + ASSERT_EQ(1, + write(self->coordinator_to_resource_pipe[1], &go_signal, 1)); + + ASSERT_EQ(1, + write(self->coordinator_to_accessor_pipe[1], &go_signal, 1)); + + close(self->coordinator_to_resource_pipe[1]); + close(self->coordinator_to_accessor_pipe[1]); + + /* Collect accessor results */ + struct { + int result; + int error; + } test_result; + + ssize_t ret =3D + read(self->result_pipe[0], &test_result, sizeof(test_result)); + ASSERT_EQ(sizeof(test_result), ret); + close(self->result_pipe[0]); + + /* Wait for both processes to complete */ + int accessor_status, resource_status; + + /* Accessor should always exit cleanly */ + ASSERT_EQ(self->accessor_pid, + waitpid(self->accessor_pid, &accessor_status, 0)); + + ASSERT_EQ(self->resource_pid, + waitpid(self->resource_pid, &resource_status, 0)); + + EXPECT_EQ(0, WEXITSTATUS(accessor_status)); + /* Determine expected behavior based on your table */ + bool should_succeed =3D (accessor_domain =3D=3D NO_SANDBOX); + + if (should_succeed) { + /* Signal should succeed across domains */ + EXPECT_EQ(0, test_result.result); /* kill() succeeds */ + /* resource receives signal */ + EXPECT_EQ(0, WEXITSTATUS(resource_status)); + } else { + /* Signal should be blocked by cross-domain isolation */ + EXPECT_EQ(-1, test_result.result); /* kill() fails */ + EXPECT_EQ(EPERM, test_result.error); /* with EPERM */ + /* resource times out */ + EXPECT_NE(0, WEXITSTATUS(resource_status)); + } +} + +/* Test for socket-based signals (SIGURG) across independent domains */ +TEST_F(cross_domain_scope, DISABLED_file_signal_cross_domain) +{ + SKIP(return, "Skip for now"); +} + TEST_HARNESS_MAIN --=20 2.43.0