[PATCH v3] selftests/landlock: Add tests for io_uring openat access control with Landlock rules

[Dorine Tipo <dorine.a.tipo@gmail.com>]

This v3 patch expands Landlock test coverage to include io_uring
operations. It also introduces a test for IORING_OP_OPENAT with Landlock
rules, verifying allowed and disallowed access. This makes sure that
IORING_OP_OPENAT is well covered from security vulnerabilities by
ensuring Landlock controls access through io_uring.

It also updates Makefile to include -luring in the LDLIBS variable.
This ensures the test code has access to the necessary library for
io_uring operations.

The patch includes several improvements to the test_ioring_openat(),
FIXTURE_SETUP() and FIXTURE_TEARDOWN() addressing feedback received on
the initial version.

Signed-off-by: Dorine Tipo <dorine.a.tipo@gmail.com>
---
Changes since V1:
V2: - Consolidated two dependent patches in the V1 series into one patch
      as suggested by Fabio.
    - Updated The subject line to be more descriptive.

V3: - Added "selftests/landlock" subject prefix
    - Revised wording in the commit message to accurately reflect the
      test functionality as suggested by Mickaël.
    - Updated the Fixture set_up and tear_down to create and remove the
      necesssary files and folders for testing access.
    - renamed allowed_ruleset_fd and disallowed_ruleset_fd to ruleset_fd
      as suggest by Mickaël.
    - Moved all variable declarations to the top of the function.
    - Refactored the code to test only one allowed and one restricted
      path instead of iterating through all the paths.
    - Added comments to explain what is happening in different blocks
      of code
    - Removed the clang-format markers.
    - Removed unused arguments in the function definition.
    - Added a final rule struct with a null path to the allowed_rule
      and disallowed_rule arrays as suggested by Fabio.
    - CC'd the missing mailing lists as suggested by Shuah.
    - All executables have been included in the .gitignore so no updates
      are necessary.

 tools/testing/selftests/landlock/Makefile  |   4 +-
 tools/testing/selftests/landlock/fs_test.c | 140 +++++++++++++++++++++
 2 files changed, 142 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/landlock/Makefile b/tools/testing/selftests/landlock/Makefile
index 348e2dbdb4e0..ab47d1dadb62 100644
--- a/tools/testing/selftests/landlock/Makefile
+++ b/tools/testing/selftests/landlock/Makefile
@@ -13,11 +13,11 @@ TEST_GEN_PROGS := $(src_test:.c=)
 TEST_GEN_PROGS_EXTENDED := true

 # Short targets:
-$(TEST_GEN_PROGS): LDLIBS += -lcap
+$(TEST_GEN_PROGS): LDLIBS += -lcap -luring
 $(TEST_GEN_PROGS_EXTENDED): LDFLAGS += -static

 include ../lib.mk

 # Targets with $(OUTPUT)/ prefix:
-$(TEST_GEN_PROGS): LDLIBS += -lcap
+$(TEST_GEN_PROGS): LDLIBS += -lcap -luring
 $(TEST_GEN_PROGS_EXTENDED): LDFLAGS += -static
diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 9a6036fbf289..7147c75b6f79 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -21,7 +21,10 @@
 #include <sys/stat.h>
 #include <sys/sysmacros.h>
 #include <sys/vfs.h>
+#include <sys/types.h>
 #include <unistd.h>
+#include <liburing.h>
+#include <linux/io_uring.h>

 #include "common.h"

@@ -4874,4 +4877,141 @@ TEST_F_FORK(layout3_fs, release_inodes)
 	ASSERT_EQ(EACCES, test_open(TMP_DIR, O_RDONLY));
 }

+/* Test io_uring's IORING_OP_OPENAT access control with landlock rules */
+static int test_ioring_op_openat(struct __test_metadata *const _metadata, const __u64 access, const char **paths)
+{
+	int ruleset_fd;
+	int ret;
+	struct io_uring ring;
+	struct io_uring_sqe *sqe;
+
+	/* Test Allowed Access */
+	const struct rule allowed_rule[] = {
+		{
+			.path = paths[0],
+			.access = access,
+		},
+		{
+			.path = NULL,
+		},
+	};
+
+	ruleset_fd = create_ruleset(_metadata, allowed_rule[0].access, allowed_rule);
+
+	ASSERT_LE(0, ruleset_fd);
+
+	ret = io_uring_queue_init(32, &ring, 0);
+
+	ASSERT_EQ(0, ret);
+
+	/* Test allowed path */
+	sqe = io_uring_get_sqe(&ring);
+
+	/* Prepare SQE  for the openat operation */
+	io_uring_prep_openat(sqe, AT_FDCWD, paths[0], O_RDONLY, ruleset_fd);
+
+	/* Verify successful SQE preparation */
+	ASSERT_EQ(0, ret);
+
+	if (ret != 0)
+		return ret;
+
+	ret = io_uring_submit(&ring);
+
+	/* Verify 1 submission completed */
+	ASSERT_EQ(1, ret);
+
+	/* Test Disallowed Access */
+	const struct rule disallowed_rule[] = {
+		{
+			.path = paths[0],
+			.access = 0,
+		},
+		{
+			.path = NULL,
+		},
+	};
+
+	ruleset_fd = create_ruleset(_metadata, disallowed_rule[0].access, disallowed_rule);
+
+	ASSERT_LE(0, ruleset_fd);
+
+	/* Test disallowed path */
+	sqe = io_uring_get_sqe(&ring);
+
+	/* Prepare SQE  for the openat operation */
+	io_uring_prep_openat(sqe, AT_FDCWD, paths[0], O_RDONLY, ruleset_fd);
+
+	/* Verify successful SQE preparation */
+	ASSERT_EQ(0, ret);
+
+	if (ret != 0)
+		return ret;
+
+	ret = io_uring_submit(&ring);
+	/* Verify 1 submission completed */
+	ASSERT_EQ(0, ret);
+
+	/*  Cleanup: close ruleset fds, etc. */
+	close(ruleset_fd);
+
+	return 0;
+}
+
+FIXTURE(openat_test) {
+	struct __test_metadata *metadata;
+	const char *allowed_paths[11];
+	const char *disallowed_paths[2];
+};
+
+FIXTURE_SETUP(openat_test)
+{
+	/* initialize metadata, allowed_paths, and disallowed_paths */
+	self->metadata = _metadata;
+	const char *temp_allowed_paths[] = {
+		file1_s1d1, file2_s1d1, file1_s1d2, file2_s1d2,
+		file1_s1d3, file2_s1d3, file1_s2d1, file1_s2d2,
+		file1_s2d3, file2_s2d3, file1_s3d1};
+
+	memcpy(self->allowed_paths, temp_allowed_paths, sizeof(temp_allowed_paths));
+
+	const char *temp_disallowed_paths[] = {dir_s3d2, dir_s3d3};
+
+	memcpy(self->disallowed_paths, temp_disallowed_paths, sizeof(temp_disallowed_paths));
+
+	/* Create necessary directories and files */
+	for (int i = 0; i < sizeof(self->allowed_paths) / sizeof(char *); i++) {
+		create_file(self->metadata, self->allowed_paths[i]);
+	}
+
+	/* Create directories for disallowed paths */
+	for (int i = 0; i < sizeof(self->disallowed_paths) / sizeof(char *); i++) {
+		create_directory(self->metadata, self->disallowed_paths[i]);
+	}
+}
+
+FIXTURE_TEARDOWN(openat_test)
+{
+	/* Clean up test environment */
+	for (int i = 0; i < sizeof(self->allowed_paths) / sizeof(char *); i++) {
+		remove_path(self->allowed_paths[i]);
+	}
+
+	for (int i = 0; i < sizeof(self->disallowed_paths) / sizeof(char *); i++) {
+		remove_path(self->disallowed_paths[i]);
+	}
+}
+
+/* Test IORING_OP_OPENAT. */
+TEST_F_FORK(openat_test, test_ioring_op_openat_allowed)
+{
+	test_ioring_op_openat(self->metadata, LANDLOCK_ACCESS_FS_READ_FILE |
+			      LANDLOCK_ACCESS_FS_WRITE_FILE, self->allowed_paths);
+}
+
+TEST_F_FORK(openat_test, test_ioring_op_openat_disallowed)
+{
+	test_ioring_op_openat(self->metadata, 0, self->disallowed_paths);
+}
+
 TEST_HARNESS_MAIN
--
2.25.1