Re: [PATCH v6 3/5] selftests/landlock: Selftests for file truncation support

On Fri, Sep 16, 2022 at 07:05:44PM +0200, Mickaël Salaün wrote:

I'd like to have tests similar to base_test.c:ruleset_fd_transfer to check
ftruncate with different kind of file descriptors and not-sandboxed
processes. That would require some code refactoring to reuse the FD passing
code.

Done. I factored out the FD sending and receiving into helper function in common.h.

On 08/09/2022 21:58, Günther Noack wrote:

quoted

diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 87b28d14a1aa..ddc8c7e57e86 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c

...
+TEST_F_FORK(layout1, truncate)
+{
+	const char *const file_rwt = file1_s1d1;
+	const char *const file_rw = file2_s1d1;
+	const char *const file_rt = file1_s1d2;
+	const char *const file_t = file2_s1d2;
+	const char *const file_none = file1_s1d3;
+	const char *const dir_t = dir_s2d1;
+	const char *const file_in_dir_t = file1_s2d1;
+	const char *const dir_w = dir_s3d1;
+	const char *const file_in_dir_w = file1_s3d1;
+	int file_rwt_fd, file_rw_fd;

These variables are unused now.

Good catch, done.

quoted

+TEST_F_FORK(layout1, ftruncate)

Great!

quoted

+{
+	/*
+	 * This test opens a new file descriptor at different stages of
+	 * Landlock restriction:
+	 *
+	 * without restriction:                    ftruncate works
+	 * something else but truncate restricted: ftruncate works
+	 * truncate restricted and permitted:      ftruncate works
+	 * truncate restricted and not permitted:  ftruncate fails
+	 *
+	 * Whether this works or not is expected to depend on the time when the
+	 * FD was opened, not to depend on the time when ftruncate() was
+	 * called.
+	 */
+	const char *const path = file1_s1d1;
+	int fd0, fd1, fd2, fd3;

You can rename them fd_layer0, fd_layer1…

Done.

quoted

+	fd0 = open(path, O_WRONLY);
+	EXPECT_EQ(0, test_ftruncate(fd0));
+
+	landlock_single_path(_metadata, path,
+			     LANDLOCK_ACCESS_FS_READ_FILE |
+				     LANDLOCK_ACCESS_FS_WRITE_FILE,
+			     LANDLOCK_ACCESS_FS_WRITE_FILE);

I'd prefer to follow the current way to write rule layers: write all struct
rule at first and then call each enforcement steps. It is a bit more verbose
but easier to understand errors. The list of test_ftruncate checks are
straightforward to follow.

Done.

quoted

+	fd1 = open(path, O_WRONLY);
+	EXPECT_EQ(0, test_ftruncate(fd0));
+	EXPECT_EQ(0, test_ftruncate(fd1));
+
+	landlock_single_path(_metadata, path, LANDLOCK_ACCESS_FS_TRUNCATE,
+			     LANDLOCK_ACCESS_FS_TRUNCATE);
+
+	fd2 = open(path, O_WRONLY);
+	EXPECT_EQ(0, test_ftruncate(fd0));
+	EXPECT_EQ(0, test_ftruncate(fd1));
+	EXPECT_EQ(0, test_ftruncate(fd2));
+
+	landlock_single_path(_metadata, path,
+			     LANDLOCK_ACCESS_FS_TRUNCATE |
+				     LANDLOCK_ACCESS_FS_WRITE_FILE,
+			     LANDLOCK_ACCESS_FS_WRITE_FILE);
+
+	fd3 = open(path, O_WRONLY);
+	EXPECT_EQ(0, test_ftruncate(fd0));
+	EXPECT_EQ(0, test_ftruncate(fd1));
+	EXPECT_EQ(0, test_ftruncate(fd2));
+	EXPECT_EQ(EACCES, test_ftruncate(fd3));
+
+	ASSERT_EQ(0, close(fd0));
+	ASSERT_EQ(0, close(fd1));
+	ASSERT_EQ(0, close(fd2));
+	ASSERT_EQ(0, close(fd3));
+}
+
  /* clang-format off */
  FIXTURE(layout1_bind) {};
  /* clang-format on */

--