[PATCH v4] Add test for io_uring openat access control with Landlock rules

[Dorine Tipo]

This v4 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 restricted O_RDONLY 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 previous implementation of tests for the io_uring operation
IORING_OP_OPENAT in the Landlock fs_test suite was found to be incorrect
and ineffective.
This patch removes the previous implementation and introduces a new set
of tests that cover both allowed and denied access scenarios.

Signed-off-by: Dorine Tipo <dorine.a.tipo at 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.

V4: - Removed the previous implementation of the tests as they were not
      correctly implemented.
---
 tools/testing/selftests/landlock/Makefile  |  4 +-
 tools/testing/selftests/landlock/fs_test.c | 85 ++++++++++++++++++++++
 2 files changed, 87 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..d1fae72e99be 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 +4877,86 @@ TEST_F_FORK(layout3_fs, release_inodes)
 	ASSERT_EQ(EACCES, test_open(TMP_DIR, O_RDONLY));
 }

+/* test openat */
+static int test_openat(struct io_uring *ring, const char *path, int dfd)
+{
+	struct io_uring_cqe *cqe;
+	struct io_uring_sqe *sqe;
+	int ret;
+
+	sqe = io_uring_get_sqe(ring);
+	if (!sqe) {
+		fprintf(stderr, "get sqe failed\n");
+		goto err;
+	}
+	io_uring_prep_openat(sqe, dfd, path, O_RDONLY, 0);
+
+	ret = io_uring_submit(ring);
+	if (ret <= 0) {
+		fprintf(stderr, "sqe submit failed: %d\n", ret);
+		goto err;
+	}
+
+	ret = io_uring_wait_cqe(ring, &cqe);
+	if (ret < 0) {
+		fprintf(stderr, "wait completion %d\n", ret);
+		goto err;
+	}
+	ret = cqe->res;
+	io_uring_cqe_seen(ring, cqe);
+	return ret;
+err:
+	return -1;
+}
+
+TEST_F_FORK(layout1, openat_allowed)
+{
+	struct io_uring ring;
+	int ret;
+	const char *path = "file1_s1d3";
+	const struct rule rules[] = {
+		{
+			.path = path,
+			.access = LANDLOCK_ACCESS_FS_READ_FILE,
+		},
+		{
+			.path = NULL,
+		},
+	};
+	int ruleset_fd;
+
+	ruleset_fd = create_ruleset(_metadata, rules[0].access, rules);
+	ret = io_uring_queue_init(8, &ring, 0);
+
+	ASSERT_EQ(0, ret);
+	ASSERT_LE(0, ruleset_fd);
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, test_openat(&ring, file1_s1d3, AT_FDCWD));
+}
+
+TEST_F_FORK(layout1, openat_denied)
+{
+	struct io_uring ring;
+	int ret;
+	const char *path = "file2_s1d3";
+	const struct rule rules[] = {
+		{
+			.path = path,
+			.access = LANDLOCK_ACCESS_FS_READ_FILE,
+		},
+		{
+			.path = NULL,
+		},
+	};
+	int ruleset_fd;
+
+	ruleset_fd = create_ruleset(_metadata, rules[0].access, rules);
+	ret = io_uring_queue_init(8, &ring, 0);
+
+	ASSERT_EQ(0, ret);
+	ASSERT_LE(0, ruleset_fd);
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(EACCES, test_openat(&ring, file1_s1d3, AT_FDCWD));
+}
+
 TEST_HARNESS_MAIN
--
2.25.1