selftests/bpf: make arg_parsing.c more robust to crashes

We started getting a crash in BPF CI, which seems to originate from
test_parse_test_list_file() test and is happening at this line:

  ASSERT_OK(strcmp("test_with_spaces", set.tests[0].name), "test 0 name");

One way we can crash there is if set.cnt zero, which is checked for with
ASSERT_EQ() above, but we proceed after this regardless of the outcome.
Instead of crashing, we should bail out with test failure early.

Similarly, if parse_test_list_file() fails, we shouldn't be even looking
at set, so bail even earlier if ASSERT_OK() fails.

Fixes: 64276f0 ("selftests/bpf: Test_progs can read test lists from file")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Tested-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Link: https://lore.kernel.org/r/20251014202037.72922-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: anakryiko

tools/testing/selftests/bpf/prog_tests/arg_parsing.c

@@ -146,9 +146,12 @@ static void test_parse_test_list_file(void)
 
 	init_test_filter_set(&set);
 
-	ASSERT_OK(parse_test_list_file(tmpfile, &set, true), "parse file");
+	if (!ASSERT_OK(parse_test_list_file(tmpfile, &set, true), "parse file"))
+		goto out_fclose;
+
+	if (!ASSERT_EQ(set.cnt, 4, "test  count"))
+		goto out_free_set;
 
-	ASSERT_EQ(set.cnt, 4, "test  count");
 	ASSERT_OK(strcmp("test_with_spaces", set.tests[0].name), "test 0 name");
 	ASSERT_EQ(set.tests[0].subtest_cnt, 0, "test 0 subtest count");
 	ASSERT_OK(strcmp("testA", set.tests[1].name), "test 1 name");
@@ -158,8 +161,8 @@ static void test_parse_test_list_file(void)
 	ASSERT_OK(strcmp("testB", set.tests[2].name), "test 2 name");
 	ASSERT_OK(strcmp("testC_no_eof_newline", set.tests[3].name), "test 3 name");
 
+out_free_set:
 	free_test_filter_set(&set);
-
 out_fclose:
 	fclose(fp);
 out_remove: