[PATCH 3/7] media: nxp: imx8-isi: Check whether crossbar pad is non-NULL before access

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

From: Marek Vasut <marex@denx.de>

When translating source to sink streams in the crossbar subdev, the
driver tries to locate the remote subdev connected to the sink pad. The
remote pad may be NULL, if userspace tries to enable a stream that ends
at an unconnected crossbar sink. When that occurs, the driver
dereferences the NULL pad, leading to a crash.

Prevent the crash by checking if the pad is NULL before using it, and
return an error if it is.

Fixes: cf21f328fcaf ("media: nxp: Add i.MX8 ISI driver")
Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/20231201150614.63300-1-marex@denx.de
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

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 792f031e032a..44354931cf8a 100644
--- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
+++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
@@ -160,8 +160,14 @@ mxc_isi_crossbar_xlate_streams(struct mxc_isi_crossbar *xbar,
 	}
 
 	pad = media_pad_remote_pad_first(&xbar->pads[sink_pad]);
-	sd = media_entity_to_v4l2_subdev(pad->entity);
+	if (!pad) {
+		dev_dbg(xbar->isi->dev,
+			"no pad connected to crossbar input %u\n",
+			sink_pad);
+		return ERR_PTR(-EPIPE);
+	}
 
+	sd = media_entity_to_v4l2_subdev(pad->entity);
 	if (!sd) {
 		dev_dbg(xbar->isi->dev,
 			"no entity connected to crossbar input %u\n",
-- 
Regards,

Laurent Pinchart