Re: [PATCH] media: nxp: imx8-isi: Check whether pad is non-NULL before access

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Maud,

On Mon, Aug 18, 2025 at 02:31:43PM +0200, Maud Spierings via B4 Relay wrote:
> From: Maud Spierings <maudspierings@gocontroll.com>
> 
> media_pad_remote_pad_first() can return NULL if no valid link is found.
> Check for this possibility before dereferencing it in the next line.
> 
> Reported/investigated in [1]:
> 
> Link: https://lore.kernel.org/all/1536a61b-b405-4762-9fb4-7e257f95e49e@gocontroll.com/ [1]
> Fixes: cf21f328fcaf ("media: nxp: Add i.MX8 ISI driver")
> Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
> ---
> I'm not sure if this should be a dev_dbg(), just following the pattern
> around it for now, also not sure if EPIPE is the correct error.

I've submitted
https://lore.kernel.org/linux-media/20250820140021.8026-1-laurent.pinchart@ideasonboard.com,
which should fix this issue in a more generic way.

> ---
>  drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> 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 ede6cc74c0234049fa225ad82aaddaad64aa53d7..1ed8b031178b7d934b04a8752747f556bd1fc5a9 100644
> --- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
> +++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
> @@ -160,6 +160,13 @@ mxc_isi_crossbar_xlate_streams(struct mxc_isi_crossbar *xbar,
>  	}
>  
>  	pad = media_pad_remote_pad_first(&xbar->pads[sink_pad]);
> +
> +	if (pad == NULL) {
> +		dev_dbg(xbar->isi->dev, "no valid link found to pad %u\n",
> +			sink_pad);
> +		return ERR_PTR(-EPIPE);
> +	}
> +
>  	sd = media_entity_to_v4l2_subdev(pad->entity);
>  	if (!sd) {
>  		dev_dbg(xbar->isi->dev,
> 
> ---
> base-commit: 3ac864c2d9bb8608ee236e89bf561811613abfce
> change-id: 20250818-imx8_isi-954898628bb6

-- 
Regards,

Laurent Pinchart