linux-kernel - Re: [PATCH v2 5/5] kunit: make kunit_kfree(NULL) a no-op to match kfree()

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Date:   Sat, 23 Jul 2022 14:33:23 +0800
From:   David Gow <davidgow@...gle.com>
To:     Daniel Latypov <dlatypov@...gle.com>
Cc:     Brendan Higgins <brendanhiggins@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        KUnit Development <kunit-dev@...glegroups.com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v2 5/5] kunit: make kunit_kfree(NULL) a no-op to match kfree()

On Sat, Jul 23, 2022 at 1:15 AM Daniel Latypov <dlatypov@...gle.com> wrote:
>
> The real kfree() function will silently return when given a NULL.
> So a user might reasonably think they can write the following code:
>   char *buffer = NULL;
>   if (param->use_buffer) buffer = kunit_kzalloc(test, 10, GFP_KERNEL);
>   ...
>   kunit_kfree(test, buffer);
>
> As-is, kunit_kfree() will mark the test as FAILED when buffer is NULL.
> (And in earlier times, it would segfault).
>
> Let's match the semantics of kfree().
>
> Suggested-by: David Gow <davidgow@...gle.com>
> Signed-off-by: Daniel Latypov <dlatypov@...gle.com>
> ---
> v1 -> v2: add this patch to the series.
> ---

Thanks! This looks good to me, and worked with a basic test.

Reviewed-by: David Gow <davidgow@...gle.com>

Cheers,
-- David

>  lib/kunit/test.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/lib/kunit/test.c b/lib/kunit/test.c
> index c7ca87484968..879c8db36cb5 100644
> --- a/lib/kunit/test.c
> +++ b/lib/kunit/test.c
> @@ -698,6 +698,9 @@ static inline bool kunit_kfree_match(struct kunit *test,
>
>  void kunit_kfree(struct kunit *test, const void *ptr)
>  {
> +       if (!ptr)
> +               return;
> +
>         if (kunit_destroy_resource(test, kunit_kfree_match, (void *)ptr))
>                 KUNIT_FAIL(test, "kunit_kfree: %px already freed or not allocated by kunit", ptr);
>  }
> --
> 2.37.1.359.gd136c6c3e2-goog
>