Input: tests - add test to cover all input_grab_device() function

Currently input_grab_device() isn't covered by any tests
Thus, adding a test to cover the cases:
1. The device is grabbed successfully
2. Trying to grab a device that is already grabbed by another input
handle

Signed-off-by: Dana Elfassy <dangel101@gmail.com>
Tested-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Link: https://lore.kernel.org/r/20230522215514.722564-1-dangel101@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Input: tests - fix input_test_match_device_id test

Properly initialize input_device_id structure in
input_test_match_device_id test to make sure it contains no garbage
causing the test to randomly fail.

Fixes: fdefcbdd6f36 ("Input: Add KUnit tests for some of the input core helper functions")
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/ZFLI7T2qZTGJ1UUK@google.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Input: tests - fix use-after-free and refcount underflow in input_test_exit()

With CONFIG_DEBUG_SLAB=y:

# Subtest: input_core
1..3
input: Test input device as /devices/virtual/input/input1
8<--- cut here ---
Unable to handle kernel paging request at virtual address 6b6b6dd7 when read
...
__lock_acquire from lock_acquire+0x26c/0x300
lock_acquire from _raw_spin_lock_irqsave+0x50/0x64
_raw_spin_lock_irqsave from devres_remove+0x20/0x7c
devres_remove from devres_destroy+0x8/0x24
devres_destroy from input_free_device+0x2c/0x60
input_free_device from kunit_try_run_case+0x70/0x94 [kunit]

Without CONFIG_DEBUG_SLAB=y:

KTAP version 1
# Subtest: input_core
1..3
input: Test input device as /devices/virtual/input/input1
------------[ cut here ]------------
WARNING: CPU: 0 PID: 694 at lib/refcount.c:28 refcount_warn_saturate+0x54/0x100
refcount_t: underflow; use-after-free.
...
Call Trace: [<0037cad4>] dump_stack+0xc/0x10
[<00377614>] __warn+0x7e/0xb4
[<0037768c>] warn_slowpath_fmt+0x42/0x62
[<001eee1c>] refcount_warn_saturate+0x54/0x100
[<000b1d34>] kfree_const+0x0/0x20
[<0036290a>] __kobject_del+0x0/0x6e
[<001eee1c>] refcount_warn_saturate+0x54/0x100
[<00362a1a>] kobject_put+0xa2/0xb6
[<11965770>] kunit_generic_run_threadfn_adapter+0x0/0x1c [kunit]

As per the comments for input_allocate_device() and
input_register_device(), input_free_device() must be called only to free
devices that have not been registered. input_unregister_device()
already calls input_put_device(), thus leading to a use-after-free.

Moreover, the kunit_suite.exit() method is called after every test case,
even on failures. As the test itself already does cleanups in its
failure paths, this may lead to a second use-after-free.

Fix the first issue by dropping the call to input_allocate_device() from
input_test_exit().
Fix the second issue by making the cleanup code conditional on a
successful test.

Fixes: fdefcbdd6f361841 ("Input: Add KUnit tests for some of the input core helper functions")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/957b3b309a44d39fb6e38b2a526b250f69ea3d2c.1683022164.git.geert+renesas@glider.be
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Input: Add KUnit tests for some of the input core helper functions

The input subsystem doesn't currently have any unit tests, let's add a
CONFIG_INPUT_KUNIT_TEST option that builds a test suite to be executed
with the KUnit test infrastructure.

For now, only three tests were added for some of the input core helper
functions that are trivial to test:

* input_test_polling: set/get poll interval and set-up a poll handler.

* input_test_timestamp: set/get input event timestamps.

* input_test_match_device_id: match a device by bus, vendor, product,
version and events capable of handling.

But having the minimal KUnit support allows to add more tests and suites
as follow-up changes. The tests can be run with the following command:

$ ./tools/testing/kunit/kunit.py run --kunitconfig=drivers/input/tests/

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Tested-by: Enric Balletbo i Serra <eballetbo@redhat.com>
config: powerpc-allnoconfig (https://download.01.org/0day-ci/archive/20230330/202303301815.kRKFM3NH-lkp@intel.com/config)
Link: https://lore.kernel.org/r/20230330081831.2291351-1-javierm@redhat.com

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>