linux-kernel - Re: [PATCH v6 5/5] media: uvcvideo: Flush the control cache when we get an event

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: <dfbbb4a1-2575-42a4-a1f9-c279fc17d9c4@redhat.com>
Date: Mon, 9 Dec 2024 16:24:50 +0100
From: Hans de Goede <hdegoede@...hat.com>
To: Ricardo Ribalda <ribalda@...omium.org>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Guennadi Liakhovetski <guennadi.liakhovetski@...el.com>,
 Hans Verkuil <hverkuil@...all.nl>,
 Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
 linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 5/5] media: uvcvideo: Flush the control cache when we
 get an event

Hi,

On 9-Dec-24 12:31 PM, Ricardo Ribalda wrote:
> Hi Hans
> 
> On Mon, 9 Dec 2024 at 12:03, Hans de Goede <hdegoede@...hat.com> wrote:
>>
>> Hi Ricardo,
>>
>> On 3-Dec-24 10:20 PM, Ricardo Ribalda wrote:
>>> Asynchronous controls trigger an event when they have completed their
>>> operation.
>>>
>>> This can make that the control cached value does not match the value in
>>> the device.
>>>
>>> Let's flush the cache to be on the safe side.
>>>
>>> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
>>
>> Thank you for your patch.
>>
>> It seems that you have missed Laurent's reply asking to improve the commit message:
>>
>> "Conceptually this change looks fine, but the commit message needs to
>> explain why this is safe to do without protecting ctrl->loaded with a
>> lock."
>>
>> https://lore.kernel.org/linux-media/20241203203748.GD5196@pendragon.ideasonboard.com/
>>
>> Or maybe the posting of this v6 and that reply have crossed each other.
> 
> In this v6 I moved loaded=0 from uvc_ctrl_status_event_async() to
> uvc_ctrl_status_event()

Ah I missed that you moved it, my bad.

> Now setting loaded=0 is just after mutex_lock(&chain->ctrl_mutex);
> 
> Do we need a new version?

Since the setting is now clearly done under the lock the new version seems
good to me as is.

So I have now merged this into:

https://gitlab.freedesktop.org/linux-media/users/uvc/-/commits/next/

Regards,

Hans

> 
>>
>> Either way please post a new version addressing this comment.
>>
>> Thanks & Regards,
>>
>> Hans
>>
>>
>>
>>> ---
>>>  drivers/media/usb/uvc/uvc_ctrl.c | 3 +++
>>>  1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
>>> index 3dc9b7a49f64..db29e0e8bfd4 100644
>>> --- a/drivers/media/usb/uvc/uvc_ctrl.c
>>> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
>>> @@ -1622,6 +1622,9 @@ void uvc_ctrl_status_event(struct uvc_video_chain *chain,
>>>
>>>       mutex_lock(&chain->ctrl_mutex);
>>>
>>> +     /* Flush the control cache, the data might have changed. */
>>> +     ctrl->loaded = 0;
>>> +
>>>       handle = ctrl->handle;
>>>       if (handle)
>>>               uvc_ctrl_set_handle(handle, ctrl, NULL);
>>>
>>
> 
>