linux-kernel - Re: BUG: double mutex_unlock in drivers/media/video/tlg2300/pd-video.c

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Date:	Wed, 22 Dec 2010 14:32:43 -0200
From:	Mauro Carvalho Chehab <mchehab@...radead.org>
To:	iceberg <strakh@...ras.ru>
CC:	linux-kernel@...r.kernel.org, kangyong@...egent.com,
	xbzhang@...egent.com, zyziii@...egent.com, shijie8@...il.com,
	linux-media@...r.kernel.org
Subject: Re: BUG: double mutex_unlock in drivers/media/video/tlg2300/pd-video.c

Em 13-12-2010 13:59, iceberg escreveu:
> KERNEL_VERSION: 2.6.36
>         SUBJECT: double mutex_lock in drivers/media/video/tlg2300/pd-video.c 
> in function vidioc_s_fmt
>         SUBSCRIBE:
> 	First mutex_unlock in function pd_vidioc_s_fmt in line 767:
> 
>  764        ret |= send_set_req(pd, VIDEO_ROSOLU_SEL,
>  765                                vid_resol, &cmd_status);
>  766        if (ret || cmd_status) {
>  767                mutex_unlock(&pd->lock);
>  768                return -EBUSY;
>  769        }
> 
> 	Second mutex_unlock in function vidioc_s_fmt in line 806:
> 
>  805        pd_vidioc_s_fmt(pd, &f->fmt.pix);
>  806        mutex_unlock(&pd->lock);
> 
> Found by Linux Device Drivers Verification Project
> 
> ?hecks the return code of pd_vidioc_s_fm before mutex_unlocking.
> 
> Signed-off-by: Alexander Strakh <strakh@...ras.ru>
> 
> ---
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> 
> diff --git a/drivers/media/video/tlg2300/pd-video.c 
> b/drivers/media/video/tlg2300/pd-video.c
> index a1ffe18..fe6bd2b 100644
> --- a/drivers/media/video/tlg2300/pd-video.c
> +++ b/drivers/media/video/tlg2300/pd-video.c
> @@ -802,8 +802,8 @@ static int vidioc_s_fmt(struct file *file, void *fh, 
> struct v4l2_format *f)
>  		return -EINVAL;
>  	}
>  
> -	pd_vidioc_s_fmt(pd, &f->fmt.pix);
> -	mutex_unlock(&pd->lock);
> +	if (!pd_vidioc_s_fmt(pd, &f->fmt.pix)) 
> +		mutex_unlock(&pd->lock);
>  	return 0;
>  }
> 

Thanks for the patch, but the better is to keep the calls to mutex_lock/mutex_unlock
at the same function. So, instead of adding an "if" at vidioc_s_fmt, please remove
the mutex_unlock() from pd_vidioc_s_fmt().

Cheers,
Mauro
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