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

[Günther Noack]

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:
> > 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.

> > +TEST_F_FORK(layout1, ftruncate)
> 
> Great!
> 
> > +{
> > +	/*
> > +	 * 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.

> > +	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.


> > +	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 */

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