[PATCH v2] kunit: fix reference count leak in kfree_at_end

[PATCH v2] kunit: fix reference count leak in kfree_at_end

[Xiyu Yang]

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_alloc_resource() instead of
kunit_alloc_and_get_resource().

Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
---
 lib/kunit/executor_test.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/kunit/executor_test.c b/lib/kunit/executor_test.c
index cdbe54b16501..c2dcfb1f6e97 100644
--- a/lib/kunit/executor_test.c
+++ b/lib/kunit/executor_test.c
@@ -116,7 +116,7 @@ static void kfree_at_end(struct kunit *test, const void *to_free)
 	/* 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,
+	kunit_alloc_resource(test, NULL, kfree_res_free, GFP_KERNEL,
 				     (void *)to_free);
 }
 
-- 
2.7.4

Re: [PATCH v2] kunit: fix reference count leak in kfree_at_end

[Daniel Latypov]

On Thu, Sep 9, 2021 at 12:26 AM '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_alloc_resource() instead of
> kunit_alloc_and_get_resource().
>
> Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>

Reviewed-by: Daniel Latypov <dlatypov@google.com>

Ah, thanks for finding and fixing this!
We really should have better documentation/otherwise make it clearer
that people shouldn't use the "_and_get" version.

I went and added some pr_info() calls to verify that these were being
leaked before and they're fixed now.

I copy-pasted this mistake into
https://lore.kernel.org/linux-kselftest/20210831171926.3832806-2-dlatypov@google.com/.
I'll send a v3 fix for that patch as well.

> ---
>  lib/kunit/executor_test.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/kunit/executor_test.c b/lib/kunit/executor_test.c
> index cdbe54b16501..c2dcfb1f6e97 100644
> --- a/lib/kunit/executor_test.c
> +++ b/lib/kunit/executor_test.c
> @@ -116,7 +116,7 @@ static void kfree_at_end(struct kunit *test, const void *to_free)
>         /* 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,
> +       kunit_alloc_resource(test, NULL, kfree_res_free, GFP_KERNEL,
>                                      (void *)to_free);
>  }
>
> --
> 2.7.4
>
> --
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Re: [PATCH v2] kunit: fix reference count leak in kfree_at_end

[Daniel Latypov]

On Thu, Sep 9, 2021 at 9:59 AM Daniel Latypov <dlatypov@google.com> wrote:
>
> On Thu, Sep 9, 2021 at 12:26 AM '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_alloc_resource() instead of
> > kunit_alloc_and_get_resource().
> >
> > Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> > Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
>
> Reviewed-by: Daniel Latypov <dlatypov@google.com>
>
> Ah, thanks for finding and fixing this!
> We really should have better documentation/otherwise make it clearer
> that people shouldn't use the "_and_get" version.
>
> I went and added some pr_info() calls to verify that these were being
> leaked before and they're fixed now.
>
> I copy-pasted this mistake into
> https://lore.kernel.org/linux-kselftest/20210831171926.3832806-2-dlatypov@google.com/.
> I'll send a v3 fix for that patch as well.

Fixed that patch:
https://lore.kernel.org/linux-kselftest/20210909171052.3192326-2-dlatypov@google.com/

I assume this patch and that one shouldn't have merge conflicts, so we
don't need these to be applied in any specific order.

>
> > ---
> >  lib/kunit/executor_test.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/lib/kunit/executor_test.c b/lib/kunit/executor_test.c
> > index cdbe54b16501..c2dcfb1f6e97 100644
> > --- a/lib/kunit/executor_test.c
> > +++ b/lib/kunit/executor_test.c
> > @@ -116,7 +116,7 @@ static void kfree_at_end(struct kunit *test, const void *to_free)
> >         /* 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,
> > +       kunit_alloc_resource(test, NULL, kfree_res_free, GFP_KERNEL,
> >                                      (void *)to_free);
> >  }
> >
> > --
> > 2.7.4
> >
> > --
> > You received this message because you are subscribed to the Google Groups "KUnit Development" group.
> > To unsubscribe from this group and stop receiving emails from it, send an email to kunit-dev+unsubscribe@googlegroups.com.
> > To view this discussion on the web visit https://groups.google.com/d/msgid/kunit-dev/1631172276-82914-1-git-send-email-xiyuyang19%40fudan.edu.cn.

Re: [PATCH v2] kunit: fix reference count leak in kfree_at_end

[Brendan Higgins]

On Thu, Sep 9, 2021 at 12:26 AM Xiyu Yang <xiyuyang19@fudan.edu.cn> 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_alloc_resource() instead of
> kunit_alloc_and_get_resource().
>
> Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>

Reviewed-by: Brendan Higgins <brendanhiggins@google.com>

Thanks!

Re: [PATCH v2] kunit: fix reference count leak in kfree_at_end

[Shuah Khan]

On 9/28/21 3:27 PM, Brendan Higgins wrote:
> On Thu, Sep 9, 2021 at 12:26 AM Xiyu Yang <xiyuyang19@fudan.edu.cn> 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_alloc_resource() instead of
>> kunit_alloc_and_get_resource().
>>
>> Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
>> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
> 
> Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
> 
> Thanks!
> 

Thank you for the fix.

Applied now after fixing a checkpatch alignment check to

git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest.git/
kunit-fixes branch.

Please remember to run checkpatch.pl before sending patches.

thanks,
-- Shuah