linux-kernel - Re: [PATCH v1 1/3] kunit: fix bug in debugfs logs of parameterized tests

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Date:   Thu, 9 Feb 2023 13:06:05 +0800
From:   David Gow <davidgow@...gle.com>
To:     Rae Moar <rmoar@...gle.com>
Cc:     brendanhiggins@...gle.com, dlatypov@...gle.com,
        skhan@...uxfoundation.org, kunit-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v1 1/3] kunit: fix bug in debugfs logs of parameterized tests

On Wed, 1 Feb 2023 at 06:04, Rae Moar <rmoar@...gle.com> wrote:
>
> Fix bug in debugfs logs that causes parameterized results to not appear
> in the log because the log is reintialized (cleared) when each parameter is

Nit: s/reintialized/reinitialized

> run.
>
> Ensure these results appear in the debugfs logs and increase log size to
> allow for the size of parameterized results.
>
> Signed-off-by: Rae Moar <rmoar@...gle.com>
> ---

This looks pretty good to me, but we may need to restrict the size of
a single log line separately from that of the whole log.

(It'd also be nice to include a before/after in the commit description.)

With the stack size issue fixed, though, this looks good to me:
Reviewed-by: David Gow <davidgow@...gle.com>

Cheers,
-- David

>  include/kunit/test.h | 2 +-
>  lib/kunit/test.c     | 3 ++-
>  2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/include/kunit/test.h b/include/kunit/test.h
> index 87ea90576b50..0a077a4c067c 100644
> --- a/include/kunit/test.h
> +++ b/include/kunit/test.h
> @@ -34,7 +34,7 @@ DECLARE_STATIC_KEY_FALSE(kunit_running);
>  struct kunit;
>
>  /* Size of log associated with test. */
> -#define KUNIT_LOG_SIZE 512
> +#define KUNIT_LOG_SIZE 1500

This is used both as the overall log size, and the size of a single
line in kunit_log_append.

As the latter involves a local 'line' array, it can bloat out stack usage.

Could we either restrict the maximum line length separately, or rework
kunit_log_append() to not use a local variable?
(I imagine we could just vsnprintf() directly into the log buffer. We
could make two sprintf calls to calculate the length required to
maintain some atomicity as well (this could open us up to
time-of-check/time-of-use vulnerabilities, but I think the
vulnerability ship has sailed if you're passing untrusted pointers
into the kunit_log macro anyway))

>
>  /* Maximum size of parameter description string. */
>  #define KUNIT_PARAM_DESC_SIZE 128
> diff --git a/lib/kunit/test.c b/lib/kunit/test.c
> index 51cae59d8aae..66ba93b8222c 100644
> --- a/lib/kunit/test.c
> +++ b/lib/kunit/test.c
> @@ -437,7 +437,6 @@ static void kunit_run_case_catch_errors(struct kunit_suite *suite,
>         struct kunit_try_catch_context context;
>         struct kunit_try_catch *try_catch;
>
> -       kunit_init_test(test, test_case->name, test_case->log);
>         try_catch = &test->try_catch;
>
>         kunit_try_catch_init(try_catch,
> @@ -533,6 +532,8 @@ int kunit_run_tests(struct kunit_suite *suite)
>                 struct kunit_result_stats param_stats = { 0 };
>                 test_case->status = KUNIT_SKIPPED;
>
> +               kunit_init_test(&test, test_case->name, test_case->log);
> +
>                 if (!test_case->generate_params) {
>                         /* Non-parameterised test. */
>                         kunit_run_case_catch_errors(suite, test_case, &test);
> --
> 2.39.1.456.gfc5497dd1b-goog
>

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