[PATCH v12 3/9] selftests/landlock: Test IOCTL support

["Günther Noack" <gnoack@google.com>]

Exercises Landlock's IOCTL feature in different combinations of
handling and permitting the LANDLOCK_ACCESS_FS_IOCTL_DEV right, and in
different combinations of using files and directories.

Signed-off-by: Günther Noack <gnoack@google.com>
---
 tools/testing/selftests/landlock/fs_test.c | 236 ++++++++++++++++++++-
 1 file changed, 233 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 0bcbbf594fd7..22229fe3e403 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -8,6 +8,7 @@
  */
 
 #define _GNU_SOURCE
+#include <asm/termbits.h>
 #include <fcntl.h>
 #include <linux/landlock.h>
 #include <linux/magic.h>
@@ -15,6 +16,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <sys/capability.h>
+#include <sys/ioctl.h>
 #include <sys/mount.h>
 #include <sys/prctl.h>
 #include <sys/sendfile.h>
@@ -23,6 +25,12 @@
 #include <sys/vfs.h>
 #include <unistd.h>
 
+/*
+ * Intentionally included last to work around header conflict.
+ * See https://sourceware.org/glibc/wiki/Synchronizing_Headers.
+ */
+#include <linux/fs.h>
+
 #include "common.h"
 
 #ifndef renameat2
@@ -735,6 +743,9 @@ static int create_ruleset(struct __test_metadata *const _metadata,
 	}
 
 	for (i = 0; rules[i].path; i++) {
+		if (!rules[i].access)
+			continue;
+
 		add_path_beneath(_metadata, ruleset_fd, rules[i].access,
 				 rules[i].path);
 	}
@@ -3443,7 +3454,7 @@ TEST_F_FORK(layout1, truncate_unhandled)
 			      LANDLOCK_ACCESS_FS_WRITE_FILE;
 	int ruleset_fd;
 
-	/* Enable Landlock. */
+	/* Enables Landlock. */
 	ruleset_fd = create_ruleset(_metadata, handled, rules);
 
 	ASSERT_LE(0, ruleset_fd);
@@ -3526,7 +3537,7 @@ TEST_F_FORK(layout1, truncate)
 			      LANDLOCK_ACCESS_FS_TRUNCATE;
 	int ruleset_fd;
 
-	/* Enable Landlock. */
+	/* Enables Landlock. */
 	ruleset_fd = create_ruleset(_metadata, handled, rules);
 
 	ASSERT_LE(0, ruleset_fd);
@@ -3752,7 +3763,7 @@ TEST_F_FORK(ftruncate, open_and_ftruncate)
 	};
 	int fd, ruleset_fd;
 
-	/* Enable Landlock. */
+	/* Enables Landlock. */
 	ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
 	ASSERT_LE(0, ruleset_fd);
 	enforce_ruleset(_metadata, ruleset_fd);
@@ -3829,6 +3840,16 @@ TEST_F_FORK(ftruncate, open_and_ftruncate_in_different_processes)
 	ASSERT_EQ(0, close(socket_fds[1]));
 }
 
+/* Invokes the FS_IOC_GETFLAGS IOCTL and returns its errno or 0. */
+static int test_fs_ioc_getflags_ioctl(int fd)
+{
+	uint32_t flags;
+
+	if (ioctl(fd, FS_IOC_GETFLAGS, &flags) < 0)
+		return errno;
+	return 0;
+}
+
 TEST(memfd_ftruncate)
 {
 	int fd;
@@ -3845,6 +3866,215 @@ TEST(memfd_ftruncate)
 	ASSERT_EQ(0, close(fd));
 }
 
+static int test_fionread_ioctl(int fd)
+{
+	size_t sz = 0;
+
+	if (ioctl(fd, FIONREAD, &sz) < 0 && errno == EACCES)
+		return errno;
+	return 0;
+}
+
+/* clang-format off */
+FIXTURE(ioctl) {};
+
+FIXTURE_SETUP(ioctl) {};
+
+FIXTURE_TEARDOWN(ioctl) {};
+/* clang-format on */
+
+FIXTURE_VARIANT(ioctl)
+{
+	const __u64 handled;
+	const __u64 allowed;
+	const mode_t open_mode;
+	/*
+	 * TCGETS is used as a characteristic device-specific IOCTL command.
+	 * The logic is the same for other IOCTL commands as well.
+	 */
+	const int expected_tcgets_result; /* terminal device IOCTL */
+	/*
+	 * FIONREAD is implemented in fs/ioctl.c for regular files,
+	 * but we do not blanket-permit it for devices.
+	 */
+	const int expected_fionread_result;
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, handled_i_allowed_none) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_IOCTL_DEV,
+	.allowed = 0,
+	.open_mode = O_RDWR,
+	.expected_tcgets_result = EACCES,
+	.expected_fionread_result = EACCES,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, handled_i_allowed_i) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_IOCTL_DEV,
+	.allowed = LANDLOCK_ACCESS_FS_IOCTL_DEV,
+	.open_mode = O_RDWR,
+	.expected_tcgets_result = 0,
+	.expected_fionread_result = 0,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(ioctl, unhandled) {
+	/* clang-format on */
+	.handled = LANDLOCK_ACCESS_FS_EXECUTE,
+	.allowed = LANDLOCK_ACCESS_FS_EXECUTE,
+	.open_mode = O_RDWR,
+	.expected_tcgets_result = 0,
+	.expected_fionread_result = 0,
+};
+
+static int test_fioqsize_ioctl(int fd)
+{
+	size_t sz;
+
+	if (ioctl(fd, FIOQSIZE, &sz) < 0)
+		return errno;
+	return 0;
+}
+
+static int test_tcgets_ioctl(int fd)
+{
+	struct termios info;
+
+	if (ioctl(fd, TCGETS, &info) < 0)
+		return errno;
+	return 0;
+}
+
+TEST_F_FORK(ioctl, handle_dir_access_file)
+{
+	const int flag = 0;
+	const struct rule rules[] = {
+		{
+			.path = "/dev",
+			.access = variant->allowed,
+		},
+		{},
+	};
+	int file_fd, ruleset_fd;
+
+	/* Enables Landlock. */
+	ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
+	ASSERT_LE(0, ruleset_fd);
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	file_fd = open("/dev/tty", variant->open_mode);
+	ASSERT_LE(0, file_fd);
+
+	/* Checks that IOCTL commands return the expected errors. */
+	EXPECT_EQ(variant->expected_tcgets_result, test_tcgets_ioctl(file_fd));
+	EXPECT_EQ(variant->expected_fionread_result,
+		  test_fionread_ioctl(file_fd));
+
+	/* Checks that unrestrictable commands are unrestricted. */
+	EXPECT_EQ(0, ioctl(file_fd, FIOCLEX));
+	EXPECT_EQ(0, ioctl(file_fd, FIONCLEX));
+	EXPECT_EQ(0, ioctl(file_fd, FIONBIO, &flag));
+	EXPECT_EQ(0, ioctl(file_fd, FIOASYNC, &flag));
+	EXPECT_EQ(ENOTTY, test_fioqsize_ioctl(file_fd));
+
+	ASSERT_EQ(0, close(file_fd));
+}
+
+TEST_F_FORK(ioctl, handle_dir_access_dir)
+{
+	const int flag = 0;
+	const struct rule rules[] = {
+		{
+			.path = "/dev",
+			.access = variant->allowed,
+		},
+		{},
+	};
+	int dir_fd, ruleset_fd;
+
+	/* Enables Landlock. */
+	ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
+	ASSERT_LE(0, ruleset_fd);
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/*
+	 * Ignore variant->open_mode for this test, as we intend to open a
+	 * directory.  If the directory can not be opened, the variant is
+	 * infeasible to test with an opened directory.
+	 */
+	dir_fd = open("/dev", O_RDONLY);
+	if (dir_fd < 0)
+		return;
+
+	/*
+	 * Checks that IOCTL commands return the expected errors.
+	 * We do not use the expected values from the fixture here.
+	 *
+	 * When using IOCTL on a directory, no Landlock restrictions apply.
+	 * TCGETS will fail anyway because it is not invoked on a TTY device.
+	 */
+	EXPECT_EQ(ENOTTY, test_tcgets_ioctl(dir_fd));
+	EXPECT_EQ(0, test_fionread_ioctl(dir_fd));
+
+	/* Checks that unrestrictable commands are unrestricted. */
+	EXPECT_EQ(0, ioctl(dir_fd, FIOCLEX));
+	EXPECT_EQ(0, ioctl(dir_fd, FIONCLEX));
+	EXPECT_EQ(0, ioctl(dir_fd, FIONBIO, &flag));
+	EXPECT_EQ(0, ioctl(dir_fd, FIOASYNC, &flag));
+	EXPECT_EQ(0, test_fioqsize_ioctl(dir_fd));
+
+	ASSERT_EQ(0, close(dir_fd));
+}
+
+TEST_F_FORK(ioctl, handle_file_access_file)
+{
+	const int flag = 0;
+	const struct rule rules[] = {
+		{
+			.path = "/dev/tty0",
+			.access = variant->allowed,
+		},
+		{},
+	};
+	int file_fd, ruleset_fd;
+
+	if (variant->allowed & LANDLOCK_ACCESS_FS_READ_DIR) {
+		SKIP(return, "LANDLOCK_ACCESS_FS_READ_DIR "
+			     "can not be granted on files");
+	}
+
+	/* Enables Landlock. */
+	ruleset_fd = create_ruleset(_metadata, variant->handled, rules);
+	ASSERT_LE(0, ruleset_fd);
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	file_fd = open("/dev/tty0", variant->open_mode);
+	ASSERT_LE(0, file_fd)
+	{
+		TH_LOG("Failed to open /dev/tty0: %s", strerror(errno));
+	}
+
+	/* Checks that IOCTL commands return the expected errors. */
+	EXPECT_EQ(variant->expected_tcgets_result, test_tcgets_ioctl(file_fd));
+	EXPECT_EQ(variant->expected_fionread_result,
+		  test_fionread_ioctl(file_fd));
+
+	/* Checks that unrestrictable commands are unrestricted. */
+	EXPECT_EQ(0, ioctl(file_fd, FIOCLEX));
+	EXPECT_EQ(0, ioctl(file_fd, FIONCLEX));
+	EXPECT_EQ(0, ioctl(file_fd, FIONBIO, &flag));
+	EXPECT_EQ(0, ioctl(file_fd, FIOASYNC, &flag));
+	EXPECT_EQ(ENOTTY, test_fioqsize_ioctl(file_fd));
+
+	ASSERT_EQ(0, close(file_fd));
+}
+
 /* clang-format off */
 FIXTURE(layout1_bind) {};
 /* clang-format on */
-- 
2.44.0.396.g6e790dbe36-goog