[PATCH v2] selftests/input: add test to cover len > maxlen in bits_to_user()

[Dana Elfassy <delfassy@redhat.com>]

In order to cover this case, setting 'maxlen = 0', with the following
explanation:
EVIOCGKEY is executed from evdev_do_ioctl(), which is called from
evdev_ioctl_handler().
evdev_ioctl_handler() is called from 2 functions, where by code coverage,
only the first one is in use.
‘compat’ is given the value ‘0’ [1].
Thus, the condition [2] is always false.
This means ‘len’ always equals a positive number [3]
‘maxlen’ in evdev_handle_get_val [4] is defined locally in
evdev_do_ioctl() [5], and is sent in the variable 'size' [6]

[1] https://elixir.bootlin.com/linux/v6.2/source/drivers/input/evdev.c#L1281
[2] https://elixir.bootlin.com/linux/v6.2/source/drivers/input/evdev.c#L705
[3] https://elixir.bootlin.com/linux/v6.2/source/drivers/input/evdev.c#L707
[4] https://elixir.bootlin.com/linux/v6.2/source/drivers/input/evdev.c#L886
[5] https://elixir.bootlin.com/linux/v6.2/source/drivers/input/evdev.c#L1155
[6] https://elixir.bootlin.com/linux/v6.2/source/drivers/input/evdev.c#L1141

Signed-off-by: Dana Elfassy <dangel101@gmail.com>
---
Changes in v2:
- Added following note about the patch's dependency 

This patch depends on '[v3] selftests/input: Introduce basic tests for evdev ioctls' [1] sent to the ML.
[1] https://patchwork.kernel.org/project/linux-input/patch/20230607153214.15933-1-eballetbo@kernel.org/

 tools/testing/selftests/input/evioc-test.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/tools/testing/selftests/input/evioc-test.c b/tools/testing/selftests/input/evioc-test.c
index ad7b93fe39cf..b94de2ee5596 100644
--- a/tools/testing/selftests/input/evioc-test.c
+++ b/tools/testing/selftests/input/evioc-test.c
@@ -234,4 +234,23 @@ TEST(eviocsrep_set_repeat_settings)
 	selftest_uinput_destroy(uidev);
 }
 
+TEST(eviocgkey_get_global_key_state)
+{
+	struct selftest_uinput *uidev;
+	int rep_values[2];
+	int rc;
+
+	memset(rep_values, 0, sizeof(rep_values));
+
+	rc = selftest_uinput_create_device(&uidev);
+	ASSERT_EQ(0, rc);
+	ASSERT_NE(NULL, uidev);
+
+	/* ioctl to create the scenario where len > maxlen in bits_to_user() */
+	rc = ioctl(uidev->evdev_fd, EVIOCGKEY(0), rep_values);
+	ASSERT_EQ(0, rc);
+
+	selftest_uinput_destroy(uidev);
+}
+
 TEST_HARNESS_MAIN
-- 
2.41.0