linux-kernel - [PATCH] kunit: fix too small allocation when using suite-only kunit.filter

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Date:   Fri,  1 Oct 2021 18:36:35 -0700
From:   Daniel Latypov <dlatypov@...gle.com>
To:     brendanhiggins@...gle.com, davidgow@...gle.com
Cc:     linux-kernel@...r.kernel.org, kunit-dev@...glegroups.com,
        linux-kselftest@...r.kernel.org, skhan@...uxfoundation.org,
        Daniel Latypov <dlatypov@...gle.com>,
        kernel test robot <oliver.sang@...el.com>
Subject: [PATCH] kunit: fix too small allocation when using suite-only kunit.filter_glob

When a user filters by a suite and not a test, e.g.
$ ./tools/testing/kunit/kunit.py run 'suite_name'

it hits this code
  const int len = strlen(filter_glob);
  ...
  parsed->suite_glob = kmalloc(len, GFP_KERNEL);
which fails to allocate space for the terminating NULL.

Somehow, it seems like we can't easily reproduce this under UML, so the
existing `parse_filter_test()` didn't catch this.

Fix this by allocating `len + 1` and switch to kzalloc() just to be a
bit more defensive. We're only going to run this code once per kernel
boot, and it should never be very long.

Also update the unit tests to be a bit more cautious.
This bug showed up as a NULL pointer dereference here:
>  KUNIT_EXPECT_STREQ(test, (const char *)filtered.start[0][0]->name, "suite0");
`filtered.start[0][0]` was NULL, and `name` is at offset 0 in the struct,
so `...->name` was also NULL.

Fixes: 3b29021ddd10 ("kunit: tool: allow filtering test cases via glob")
Reported-by: kernel test robot <oliver.sang@...el.com>
Signed-off-by: Daniel Latypov <dlatypov@...gle.com>
---
 lib/kunit/executor.c      | 2 +-
 lib/kunit/executor_test.c | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/kunit/executor.c b/lib/kunit/executor.c
index bab3ab940acc..1d7fecd33261 100644
--- a/lib/kunit/executor.c
+++ b/lib/kunit/executor.c
@@ -33,7 +33,7 @@ static void kunit_parse_filter_glob(struct kunit_test_filter *parsed,
 	const char *period = strchr(filter_glob, '.');
 
 	if (!period) {
-		parsed->suite_glob = kmalloc(len, GFP_KERNEL);
+		parsed->suite_glob = kzalloc(len + 1, GFP_KERNEL);
 		parsed->test_glob = NULL;
 		strcpy(parsed->suite_glob, filter_glob);
 		return;
diff --git a/lib/kunit/executor_test.c b/lib/kunit/executor_test.c
index e6323f398dfa..7d2b8dc668b1 100644
--- a/lib/kunit/executor_test.c
+++ b/lib/kunit/executor_test.c
@@ -149,6 +149,7 @@ static void filter_suites_test(struct kunit *test)
 
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, filtered.start);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, filtered.start[0]);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, filtered.start[0][0]);
 	KUNIT_EXPECT_STREQ(test, (const char *)filtered.start[0][0]->name, "suite0");
 }
 

base-commit: 3b29021ddd10cfb6b2565c623595bd3b02036f33
-- 
2.33.0.800.g4c38ced690-goog