kunit: bail out of test filtering logic quicker if OOM

When filtering what tests to run (suites and/or cases) via
kunit.filter_glob (e.g. kunit.py run <glob>), we allocate copies of
suites.

These allocations can fail, and we largely don't handle that.
Note: realistically, this probably doesn't matter much.
We're not allocating much memory and this happens early in boot, so if
we can't do that, then there's likely far bigger problems.

This patch makes us immediately bail out from the top-level function
(kunit_filter_suites) with -ENOMEM if any of the underlying kmalloc()
calls return NULL.

Implementation note: we used to return NULL pointers from some functions
to indicate either that all suites/tests were filtered out or there was
an error allocating the new array.

We'll log a short error in this case and not run any tests or print a
TAP header. From a kunit.py user's perspective, they'll get a message
about missing/invalid TAP output and have to dig into the test.log to
see it. Since hitting this error seems so unlikely, it's probably fine
to not invent a way to plumb this error message more visibly.

See also: https://lore.kernel.org/linux-kselftest/20220329103919.2376818-1-lv.ruyi@zte.com.cn/

Signed-off-by: Daniel Latypov <dlatypov@google.com>
Reported-by: Zeal Robot <zealci@zte.com.cn>
Reported-by: Lv Ruyi <lv.ruyi@zte.com.cn>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

lib/kunit/executor.c

@@ -71,9 +71,13 @@ kunit_filter_tests(struct kunit_suite *const suite, const char *test_glob)
 
 	/* Use memcpy to workaround copy->name being const. */
 	copy = kmalloc(sizeof(*copy), GFP_KERNEL);
+	if (!copy)
+		return ERR_PTR(-ENOMEM);
 	memcpy(copy, suite, sizeof(*copy));
 
 	filtered = kcalloc(n + 1, sizeof(*filtered), GFP_KERNEL);
+	if (!filtered)
+		return ERR_PTR(-ENOMEM);
 
 	n = 0;
 	kunit_suite_for_each_test_case(suite, test_case) {
@@ -106,14 +110,16 @@ kunit_filter_subsuite(struct kunit_suite * const * const subsuite,
 
 	filtered = kmalloc_array(n + 1, sizeof(*filtered), GFP_KERNEL);
 	if (!filtered)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	n = 0;
 	for (i = 0; subsuite[i] != NULL; ++i) {
 		if (!glob_match(filter->suite_glob, subsuite[i]->name))
 			continue;
 		filtered_suite = kunit_filter_tests(subsuite[i], filter->test_glob);
-		if (filtered_suite)
+		if (IS_ERR(filtered_suite))
+			return ERR_CAST(filtered_suite);
+		else if (filtered_suite)
 			filtered[n++] = filtered_suite;
 	}
 	filtered[n] = NULL;
@@ -146,7 +152,8 @@ static void kunit_free_suite_set(struct suite_set suite_set)
 }
 
 static struct suite_set kunit_filter_suites(const struct suite_set *suite_set,
-					    const char *filter_glob)
+					    const char *filter_glob,
+					    int *err)
 {
 	int i;
 	struct kunit_suite * const **copy, * const *filtered_subsuite;
@@ -166,6 +173,10 @@ static struct suite_set kunit_filter_suites(const struct suite_set *suite_set,
 
 	for (i = 0; i < max; ++i) {
 		filtered_subsuite = kunit_filter_subsuite(suite_set->start[i], &filter);
+		if (IS_ERR(filtered_subsuite)) {
+			*err = PTR_ERR(filtered_subsuite);
+			return filtered;
+		}
 		if (filtered_subsuite)
 			*copy++ = filtered_subsuite;
 	}
@@ -236,9 +247,15 @@ int kunit_run_all_tests(void)
 		.start = __kunit_suites_start,
 		.end = __kunit_suites_end,
 	};
+	int err;
 
-	if (filter_glob_param)
-		suite_set = kunit_filter_suites(&suite_set, filter_glob_param);
+	if (filter_glob_param) {
+		suite_set = kunit_filter_suites(&suite_set, filter_glob_param, &err);
+		if (err) {
+			pr_err("kunit executor: error filtering suites: %d\n", err);
+			return err;
+		}
+	}
 
 	if (!action_param)
 		kunit_exec_run_tests(&suite_set);

lib/kunit/executor_test.c

@@ -137,14 +137,16 @@ static void filter_suites_test(struct kunit *test)
 		.end = suites + 2,
 	};
 	struct suite_set filtered = {.start = NULL, .end = NULL};
+	int err = 0;
 
 	/* Emulate two files, each having one suite */
 	subsuites[0][0] = alloc_fake_suite(test, "suite0", dummy_test_cases);
 	subsuites[1][0] = alloc_fake_suite(test, "suite1", dummy_test_cases);
 
 	/* Filter out suite1 */
-	filtered = kunit_filter_suites(&suite_set, "suite0");
+	filtered = kunit_filter_suites(&suite_set, "suite0", &err);
 	kfree_subsuites_at_end(test, &filtered); /* let us use ASSERTs without leaking */
+	KUNIT_EXPECT_EQ(test, err, 0);
 	KUNIT_ASSERT_EQ(test, filtered.end - filtered.start, (ptrdiff_t)1);
 
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, filtered.start);