mm/damon/tests/core-kunit: handle alloc failures on damon_test_split_regions_of()

damon_test_split_regions_of() is assuming all dynamic memory allocation in
it will succeed.  Those are indeed likely in the real use cases since
those allocations are too small to fail, but theoretically those could
fail.  In the case, inappropriate memory access can happen.  Fix it by
appropriately cleanup pre-allocated memory and skip the execution of the
remaining tests in the failure cases.

Link: https://lkml.kernel.org/r/20251101182021.74868-9-sj@kernel.org
Fixes: 17ccae8 ("mm/damon: add kunit tests")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: David Gow <davidgow@google.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: <stable@vger.kernel.org>	[5.15+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: sjp38

mm/damon/tests/core-kunit.h

@@ -278,15 +278,35 @@ static void damon_test_split_regions_of(struct kunit *test)
 	struct damon_target *t;
 	struct damon_region *r;
 
+	if (!c)
+		kunit_skip("ctx alloc fail");
 	t = damon_new_target();
+	if (!t) {
+		damon_destroy_ctx(c);
+		kunit_skip(test, "target alloc fail");
+	}
 	r = damon_new_region(0, 22);
+	if (!r) {
+		damon_destroy_ctx(c);
+		damon_free_target(t);
+		kunit_skip(test, "region alloc fail");
+	}
 	damon_add_region(r, t);
 	damon_split_regions_of(t, 2, DAMON_MIN_REGION);
 	KUNIT_EXPECT_LE(test, damon_nr_regions(t), 2u);
 	damon_free_target(t);
 
 	t = damon_new_target();
+	if (!t) {
+		damon_destroy_ctx(c);
+		kunit_skip(test, "second target alloc fail");
+	}
 	r = damon_new_region(0, 220);
+	if (!r) {
+		damon_destroy_ctx(c);
+		damon_free_target(t);
+		kunit_skip(test, "second region alloc fail");
+	}
 	damon_add_region(r, t);
 	damon_split_regions_of(t, 4, DAMON_MIN_REGION);
 	KUNIT_EXPECT_LE(test, damon_nr_regions(t), 4u);