apparmor: fix use of strcpy in policy_unpack_test

Replace the use of strcpy() in build_aa_ext_struct() in
policy_unpack_test.c with strscpy().

strscpy() is the safer method to use to ensure the buffer does not
overflow. This was found by kernel test robot:
https://lore.kernel.org/all/202301040348.NbfVsXO0-lkp@intel.com/.

Reported-by: kernel test robot <lkp@intel.com>

Signed-off-by: Rae Moar <rmoar@google.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

apparmor: Fix uninitialized symbol 'array_size' in policy_unpack_test.c

Make sure array_size is initialized in the kunit test to get rid of
compiler warnings. This will also make sure the following tests fail
consistently if the first test fails.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

apparmor: Fix kunit test for out of bounds array

The apparmor kunit tests are failing on the out of bounds array check
with the following failure

# policy_unpack_test_unpack_array_out_of_bounds: EXPECTATION FAILED at security/apparmor/policy_unpack_test.c:178
Expected unpack_array(puf->e, name, &array_size) == 1, but
unpack_array(puf->e, name, &array_size) == -1
# policy_unpack_test_unpack_array_out_of_bounds: EXPECTATION FAILED at security/apparmor/policy_unpack_test.c:180
Expected array_size == 0, but
array_size == 64192
not ok 5 - policy_unpack_test_unpack_array_out_of_bounds

This is because unpack_array changed to allow distinguishing between
the array not being present and an error. In the error case the array
size is not set and should not be tested.

Reported-by: kernel test robot <yujie.liu@intel.com>
Fixes: 995a5b64620e ("apparmor: make unpack_array return a trianary value")
Signed-off-by: John Johansen <john.johansen@canonical.com>

apparmor: make unpack_array return a trianary value

currently unpack_array() does not return an error nor whether the
array is not present. The ability to detect an error or the array
not being present is needed so rework the unpack_array() to return
the needed information.

Signed-off-by: John Johansen <john.johansen@canonical.com>

apparmor: test: make static symbols visible during kunit testing

Use macros, VISIBLE_IF_KUNIT and EXPORT_SYMBOL_IF_KUNIT, to allow
static symbols to be conditionally set to be visible during
apparmor_policy_unpack_test, which removes the need to include the testing
file in the implementation file.

Change the namespace of the symbols that are now conditionally visible (by
adding the prefix aa_) to avoid confusion with symbols of the same name.

Allow the test to be built as a module and namespace the module name from
policy_unpack_test to apparmor_policy_unpack_test to improve clarity of
the module name.

Provide an example of how static symbols can be dealt with in testing.

Signed-off-by: Rae Moar <rmoar@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

apparmor: test: Remove some casts which are no-longer required

With some of the stricter type checking in KUnit's EXPECT macros
removed, several casts in policy_unpack_test are no longer required.

Remove the unnecessary casts, making the conditions clearer.

Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: David Gow <davidgow@google.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

apparmor: resolve uninitialized symbol warnings in policy_unpack_test.c

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mike Salvatore <mike.salvatore@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

apparmor: test: Remove some casts which are no-longer required

With some of the stricter type checking in KUnit's EXPECT macros
removed, several casts in policy_unpack_test are no longer required.

Remove the unnecessary casts, making the conditions clearer.

Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

apparmor: test: Use NULL macros

Replace the PTR_EQ NULL checks with the more idiomatic and specific NULL
macros.

Acked-by: Daniel Latypov <dlatypov@google.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Acked-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

apparmor: add AppArmor KUnit tests for policy unpack

Add KUnit tests to test AppArmor unpacking of userspace policies.
AppArmor uses a serialized binary format for loading policies. To find
policy format documentation see
Documentation/admin-guide/LSM/apparmor.rst.

In order to write the tests against the policy unpacking code, some
static functions needed to be exposed for testing purposes. One of the
goals of this patch is to establish a pattern for which testing these
kinds of functions should be done in the future.

Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Mike Salvatore <mike.salvatore@canonical.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>