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From:   David Gow <davidgow@google.com>
Date:   Thu, 9 Sep 2021 14:54:03 +0800
Message-ID: <CABVgOSkbmS_EHtTdzmk8CVY8Gm-M9hUWRuUBt+4ZLt2-txy_Aw@mail.gmail.com>
Subject: Re: [PATCH] kunit: fix reference count leak in kfree_at_end
To:     Xiyu Yang <xiyuyang19@fudan.edu.cn>
Cc:     Brendan Higgins <brendanhiggins@google.com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>,
        KUnit Development <kunit-dev@googlegroups.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        yuanxzhang@fudan.edu.cn, Xin Tan <tanxin.ctf@gmail.com>,
        Daniel Latypov <dlatypov@google.com>
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On Thu, Sep 9, 2021 at 1:28 PM 'Xiyu Yang' via KUnit Development
<kunit-dev@googlegroups.com> wrote:
>
> The reference counting issue happens in the normal path of
> kfree_at_end(). When kunit_alloc_and_get_resource() is invoked, the
> function forgets to handle the returned resource object, whose refcount
> increased inside, causing a refcount leak.
>
> Fix this issue by calling kunit_put_resource() at the end of function.
>
> Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
> ---

Thanks for looking into this.

+ Daniel -- any thoughts?

>  lib/kunit/executor_test.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/lib/kunit/executor_test.c b/lib/kunit/executor_test.c
> index cdbe54b16501..3af30abad826 100644
> --- a/lib/kunit/executor_test.c
> +++ b/lib/kunit/executor_test.c
> @@ -113,11 +113,13 @@ static void kfree_res_free(struct kunit_resource *res)
>   */
>  static void kfree_at_end(struct kunit *test, const void *to_free)
>  {
> +       struct kunit_resource *res;
>         /* kfree() handles NULL already, but avoid allocating a no-op cleanup. */
>         if (IS_ERR_OR_NULL(to_free))
>                 return;
> -       kunit_alloc_and_get_resource(test, NULL, kfree_res_free, GFP_KERNEL,
> +       res = kunit_alloc_and_get_resource(test, NULL, kfree_res_free, GFP_KERNEL,
>                                      (void *)to_free);
> +       kunit_put_resource(res);

Why not just change this to kunit_alloc_resource()?

>  }
>
>  static struct kunit_suite *alloc_fake_suite(struct kunit *test,
> --
> 2.7.4
>
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