linux-kernel - Re: [PATCH] pvrusb2: Fix oops on tear-down when radio support is not present

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Message-ID: <5491a24e-e41a-5d11-7ac5-6d6804989550@xs4all.nl>
Date:   Wed, 6 Nov 2019 08:29:47 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Mike Isely at pobox <isely@...ox.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pvrusb2: Fix oops on tear-down when radio support is not
 present

Hi Mike,

For some reason your mailer didn't include a "From:" line, only a "Reply-To:"
line. This means that the patch authorship is not detected by patchwork and
git. Can you repost with a valid From: line in the email header?

Thanks!

	Hans

On 11/6/19 3:36 AM,  wrote:
> In some device configurations there's no radio or radio support in the
> driver.  That's OK, as the driver sets itself up accordingly.  However
> on tear-down in these caes it's still trying to tear down radio
> related context when there isn't anything there, leading to
> dereferences through a null pointer and chaos follows.
> 
> How this bug survived unfixed for 11 years in the pvrusb2 driver is a
> mystery to me.
> 
> Signed-off-by: Mike Isely <isely@...ox.com>
> ---
>  drivers/media/usb/pvrusb2/pvrusb2-v4l2.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/usb/pvrusb2/pvrusb2-v4l2.c b/drivers/media/usb/pvrusb2/pvrusb2-v4l2.c
> index aa4fbc3e88cc..339119f6cc23 100644
> --- a/drivers/media/usb/pvrusb2/pvrusb2-v4l2.c
> +++ b/drivers/media/usb/pvrusb2/pvrusb2-v4l2.c
> @@ -909,8 +909,12 @@ static void pvr2_v4l2_internal_check(struct pvr2_channel *chp)
>  	pvr2_v4l2_dev_disassociate_parent(vp->dev_video);
>  	pvr2_v4l2_dev_disassociate_parent(vp->dev_radio);
>  	if (!list_empty(&vp->dev_video->devbase.fh_list) ||
> -	    !list_empty(&vp->dev_radio->devbase.fh_list))
> +	    ((vp->dev_radio != NULL) &&
> +	     !list_empty(&vp->dev_radio->devbase.fh_list))) {
> +		pvr2_trace(PVR2_TRACE_STRUCT,
> +			   "pvr2_v4l2 internal_check exit-empty id=%p", vp);
>  		return;
> +	}
>  	pvr2_v4l2_destroy_no_lock(vp);
>  }
>  
> @@ -946,7 +950,8 @@ static int pvr2_v4l2_release(struct file *file)
>  	kfree(fhp);
>  	if (vp->channel.mc_head->disconnect_flag &&
>  	    list_empty(&vp->dev_video->devbase.fh_list) &&
> -	    list_empty(&vp->dev_radio->devbase.fh_list)) {
> +	    ((vp->dev_radio == NULL) ||
> +	     list_empty(&vp->dev_radio->devbase.fh_list))) {
>  		pvr2_v4l2_destroy_no_lock(vp);
>  	}
>  	return 0;
>