kunit: test_dev_action: Correctly cast 'priv' pointer to long*

The previous implementation incorrectly assumed the original type of
'priv' was void**, leading to an unnecessary and misleading
cast. Correct the cast of the 'priv' pointer in test_dev_action() to
its actual type, long*, removing an unnecessary cast.

As an additional benefit, this fixes an out-of-bounds CHERI fault on
hardware with architectural capabilities. The original implementation
tried to store a capability-sized pointer using the priv
pointer. However, the priv pointer's capability only granted access to
the memory region of its original long type, leading to a bounds
violation since the size of a long is smaller than the size of a
capability. This change ensures that the pointer usage respects the
capabilities' bounds.

Link: https://lore.kernel.org/r/[email protected]
Fixes: d03c720 ("kunit: Add APIs for managing devices")
Reviewed-by: David Gow <[email protected]>
Signed-off-by: Florian Schmaus <[email protected]>
Signed-off-by: Shuah Khan <[email protected]>

Author: Flowdalic

lib/kunit/kunit-test.c

@@ -739,7 +739,7 @@ static struct kunit_case kunit_current_test_cases[] = {
 
 static void test_dev_action(void *priv)
 {
-	*(void **)priv = (void *)1;
+	*(long *)priv = 1;
 }
 
 static void kunit_device_test(struct kunit *test)