linux-kernel - Re: [PATCH 1/4] media: cec-notifier: fix possible object reference leak

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Message-ID: <3ed515b78a404ec4a22b5f69ed9d6e28@XCH-ALN-012.cisco.com>
Date:   Mon, 11 Feb 2019 10:38:53 +0000
From:   "Hans Verkuil (hansverk)" <hansverk@...co.com>
To:     Wen Yang <yellowriver2010@...mail.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
CC:     Linux Media Mailing List <linux-media@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] media: cec-notifier: fix possible object reference
 leak

On 09/02/2019 03:48, Wen Yang wrote:
> put_device() should be called in cec_notifier_release(),
> since the dev is being passed down to cec_notifier_get_conn(),
> which holds reference. On cec_notifier destruction, it
> should drop the reference to the device.
> 
> Fixes: 6917a7b77413 ("[media] media: add CEC notifier support")
> Signed-off-by: Wen Yang <yellowriver2010@...mail.com>
> ---
>  drivers/media/cec/cec-notifier.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/media/cec/cec-notifier.c b/drivers/media/cec/cec-notifier.c
> index dd2078b..621d4ae 100644
> --- a/drivers/media/cec/cec-notifier.c
> +++ b/drivers/media/cec/cec-notifier.c
> @@ -66,6 +66,7 @@ static void cec_notifier_release(struct kref *kref)
>  		container_of(kref, struct cec_notifier, kref);
>  
>  	list_del(&n->head);
> +	put_device(n->dev);
>  	kfree(n->conn);
>  	kfree(n);
>  }
> 

Sorry, no. The dev pointer is just a search key that the notifier code looks
for. It is not the notifier's responsibility to take a reference, that would
be the responsibility of the hdmi and cec drivers.

If you can demonstrate that there is an object reference leak, then please
provide the details: it is likely a bug elsewhere and not in the notifier
code.

BTW, your patch series didn't arrive on the linux-media mailinglist for
some reason.

Regards,

	Hans