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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <6b7fc837599e4069b876b32473b31746@XCH-ALN-012.cisco.com>
Date:   Mon, 11 Feb 2019 10:57:31 +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 11/02/2019 11:38, Hans Verkuil (hansverk) wrote:
> 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.

Correction: the cec driver should never take a reference of the hdmi device.
It never accesses the HDMI device, it only needs the HDMI device pointer as
a key in the notifier list.

The real problem is that several CEC drivers take a reference of the HDMI device
and never release it. So those drivers need to be fixed.

Regards,

	Hans

> 
> 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
>