linux-kernel - Re: [PATCH] media: usbtv: Lock resolution while streaming

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 for Android: free password hash cracker in your pocket

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

Message-ID: <89174255-aed8-4549-a329-b7782cfeec74@jjverkuil.nl>
Date: Tue, 17 Jun 2025 10:05:35 +0200
From: Hans Verkuil <hans@...erkuil.nl>
To: Ludwig Disterhof <ludwig@...terhof.eu>, linux-media@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: mchehab@...nel.org, hverkuil@...all.nl
Subject: Re: [PATCH] media: usbtv: Lock resolution while streaming

Hi Ludwig,

I'm taking this patch, but with one change:

On 28/04/2025 20:16, Ludwig Disterhof wrote:
> When an program is streaming (ffplay) and another program (qv4l2)
> changes the TV standard from NTSC to PAL, the kernel crashes due to trying
> to copy to unmapped memory.
> 
> Changing from NTSC to PAL increases the resolution in the usbtv struct,
> but the video plane buffer isn't adjusted, so it overflows.
> 
> Fixes: 0e0fe3958fdd13d ("[media] usbtv: Add support for PAL video source")
> 
> Signed-off-by: Ludwig Disterhof <ludwig@...terhof.eu>
> ---
>  drivers/media/usb/usbtv/usbtv-video.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/media/usb/usbtv/usbtv-video.c b/drivers/media/usb/usbtv/usbtv-video.c
> index be22a9697197..965a8ae82afe 100644
> --- a/drivers/media/usb/usbtv/usbtv-video.c
> +++ b/drivers/media/usb/usbtv/usbtv-video.c
> @@ -73,6 +73,10 @@ static int usbtv_configure_for_norm(struct usbtv *usbtv, v4l2_std_id norm)
>  	}
>  
>  	if (params) {
> +		if (vb2_is_streaming(&usbtv->vb2q) &&

This should be vb2_is_busy(), not vb2_is_streaming().

is_busy() checks if buffers have been allocated since in that case you can't
make changes to the resolution until all buffers are released.

No need to do anything, I've made this change myself.

Regards,

	Hans

> +		    (usbtv->width != params->cap_width ||
> +		     usbtv->height != params->cap_height))
> +			return -EBUSY;
>  		usbtv->width = params->cap_width;
>  		usbtv->height = params->cap_height;
>  		usbtv->n_chunks = usbtv->width * usbtv->height