possible bug (or not clear coding) in uvc_v4l2.c

possible bug (or not clear coding) in uvc_v4l2.c

[Jozef Vesely]

Good day, 

I am sorry to disturb you, I have been reading through uvc driver source 
and this caught my eye:
http://lxr.linux.no/#linux+v3.3/drivers/media/video/uvc/uvc_v4l2.c#L671

678: int pin = 0;
...
689: } else if (pin < selector->bNrInPins) {
...
690: pin = selector->baSourceID[index];

pin is always 0 in the comparison, was this intended?
(wasn't the line 690 supposed to be before the comparison?
or the index to be compared  to bNrInPins?)

Please excuse me wasting your tine if it is a total nonsense. 
Sincerely 

Jozef Vesely
vesely@gjh.sk

PS: I am looking for a reason why MJPEG stopped working
on my cameras (long time ago), any hints?

Re: possible bug (or not clear coding) in uvc_v4l2.c

[Laurent Pinchart]

Hi Jozef,

On Tuesday 20 March 2012 17:02:51 Jozef Vesely wrote:
> Good day,
> 
> I am sorry to disturb you, I have been reading through uvc driver source
> and this caught my eye:
> http://lxr.linux.no/#linux+v3.3/drivers/media/video/uvc/uvc_v4l2.c#L671
> 
> 678: int pin = 0;
> ...
> 689: } else if (pin < selector->bNrInPins) {
> ...
> 690: pin = selector->baSourceID[index];
> 
> pin is always 0 in the comparison, was this intended?
> (wasn't the line 690 supposed to be before the comparison?
> or the index to be compared  to bNrInPins?)
> 
> Please excuse me wasting your tine if it is a total nonsense.

It's not a waste of time at all. Thank you for the report.

The following patch should fix the problem.

commit 578ac85ae011ed5d1f3aeebcb511509c84792f23
Author: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Date:   Wed Mar 21 13:50:36 2012 +0100

    uvcvideo: Fix ENUMINPUT handling
    
    Properly validate the user-supplied index against the number of inputs.
    The code used the pin local variable instead of the index by mistake.
    
    Reported-by: Jozef Vesely <vesely@gjh.sk>
    Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
    Cc: stable@vger.kernel.org

diff --git a/drivers/media/video/uvc/uvc_v4l2.c b/drivers/media/video/uvc/uvc_v4l2.c
index 111bfff..a6b9491 100644
--- a/drivers/media/video/uvc/uvc_v4l2.c
+++ b/drivers/media/video/uvc/uvc_v4l2.c
@@ -687,7 +687,7 @@ static long uvc_v4l2_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 					break;
 			}
 			pin = iterm->id;
-		} else if (pin < selector->bNrInPins) {
+		} else if (index < selector->bNrInPins) {
 			pin = selector->baSourceID[index];
 			list_for_each_entry(iterm, &chain->entities, chain) {
 				if (!UVC_ENTITY_IS_ITERM(iterm))

I will push it to mainline.

> PS: I am looking for a reason why MJPEG stopped working on my cameras (long
>> time ago), any hints?

Not as such. Could you please provide me with more information ? You can drop
the linux-kernel CC and add linux-uvc-devel@lists.sourceforge.net
(subscriber-only at the moment) or linux-media@vger.kernel.org instead.

-- 
Regards,

Laurent Pinchart