Re: [PATCH 1/5] media: nxp: imx8-isi: Fix stream ID validation bypass in crossbar routing

[Frank Li]

On Mon, Jun 29, 2026 at 03:44:55PM +0800, Guoniu Zhou wrote:
> The crossbar routing validation has a critical bug where it validates
> the wrong routing table, allowing userspace to bypass validation entirely.
>
> The __mxc_isi_crossbar_set_routing() function is called to validate and
> apply a new routing table from userspace. However, the validation loop
> iterates over state->routing (the currently active routing table) instead
> of the routing parameter (the new table being validated):
>
>     for_each_active_route(&state->routing, route) {
>
> This means userspace can submit any invalid routing configuration and it
> will pass validation as long as the currently active routing is valid.
> This is a security issue as it allows userspace to configure routes that
> violate hardware constraints, potentially causing undefined hardware
> behavior.
>
> Fix by validating the routing table that will actually be applied:
>
>     for_each_active_route(routing, route) {
>
> Additionally, add validation to enforce hardware constraints that were
> previously missing:
> - SOURCE stream must be 0 (ISI pipes are hardcoded to stream 0)
> - SINK stream must be less than the ISI channel count
> - Memory input can only route to the first pipeline (existing check)

Please use two patches to fix one, one fix for_each_active_route()
other other fix others.

Frank
>
> Fixes: cf21f328fcaf ("media: nxp: Add i.MX8 ISI driver")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Guoniu Zhou <guoniu.zhou@xxxxxxxxxxx>
> ---
>  .../platform/nxp/imx8-isi/imx8-isi-crossbar.c      | 24 ++++++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c b/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
> index c580c831972e..29f14d30dbbb 100644
> --- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
> +++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
> @@ -106,8 +106,28 @@ static int __mxc_isi_crossbar_set_routing(struct v4l2_subdev *sd,
>  	if (ret)
>  		return ret;
>
> -	/* The memory input can be routed to the first pipeline only. */
> -	for_each_active_route(&state->routing, route) {
> +	/*
> +	 * Validate routes against hardware constraints:
> +	 * - SOURCE stream must be 0 (pipes are hardcoded to stream 0)
> +	 * - SINK stream must be < ISI channel count
> +	 * - Memory input can only route to the first pipeline
> +	 */
> +	for_each_active_route(routing, route) {
> +		if (route->source_stream != 0) {
> +			dev_dbg(xbar->isi->dev,
> +				"route to pipe %u must use source_stream=0, got %u\n",
> +				route->source_pad - xbar->num_sinks,
> +				route->source_stream);
> +			return -ENXIO;
> +		}
> +
> +		if (route->sink_stream >= xbar->num_sources) {
> +			dev_dbg(xbar->isi->dev,
> +				"sink_stream %u exceeds hardware limit %u\n",
> +				route->sink_stream, xbar->num_sources - 1);
> +			return -ENXIO;
> +		}
> +
>  		if (route->sink_pad == xbar->num_sinks - 1 &&
>  		    route->source_pad != xbar->num_sinks) {
>  			dev_dbg(xbar->isi->dev,
>
> --
> 2.34.1
>
>