Re: [PATCH 07/10] Input: synaptics-rmi4 - check V4L2 buffer size in F54 queue

[Hans Verkuil <hverkuil+cisco@kernel.org>]

On 26/06/2026 07:17, Dmitry Torokhov wrote:
> Add a safety check in rmi_f54_buffer_queue() to ensure that the
> requested report size (f54->report_size) does not exceed the actual
> allocated size of the V4L2 buffer (vb2_plane_size()).
> 
> This provides a defense-in-depth measure against any potential size
> mismatches between the V4L2 queue and the driver's internal state.
> 
> Fixes: 3a762dbd5347 ("[media] Input: synaptics-rmi4 - add support for F54 diagnostics")
> Cc: stable@vger.kernel.org
> Assisted-by: Antigravity:gemini-3.5-flash
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> ---
>  drivers/input/rmi4/rmi_f54.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/input/rmi4/rmi_f54.c b/drivers/input/rmi4/rmi_f54.c
> index c86bc81845bb..93526feea563 100644
> --- a/drivers/input/rmi4/rmi_f54.c
> +++ b/drivers/input/rmi4/rmi_f54.c
> @@ -354,6 +354,13 @@ static void rmi_f54_buffer_queue(struct vb2_buffer *vb)
>  		goto data_done;
>  	}
>  
> +	if (f54->report_size > vb2_plane_size(vb, 0)) {
> +		dev_err(&f54->fn->dev, "Buffer too small (%lu < %d)\n",
> +			vb2_plane_size(vb, 0), f54->report_size);
> +		state = VB2_BUF_STATE_ERROR;
> +		goto data_done;
> +	}
> +

That's the wrong place, it's too late for that check.

This should be checked in the buf_prepare callback. See e.g.
drivers/media/test-drivers/vivid/vivid-touch-cap.c.

Regards,

	Hans

>  	memcpy(ptr, f54->report_data, f54->report_size);
>  	vb2_set_plane_payload(vb, 0, rmi_f54_get_report_size(f54));
>  	state = VB2_BUF_STATE_DONE;