media: v4l: ioctl: Validate num_planes for debug messages

The num_planes field in struct v4l2_pix_format_mplane is used in a loop
before validating it. As the use is printing a debug message in this case,
just cap the value to the maximum allowed.

Signed-off-by: Sakari Ailus <[email protected]>
Cc: [email protected]
Reviewed-by: Thierry Reding <[email protected]>
Signed-off-by: Hans Verkuil <[email protected]>
Cc: <[email protected]>      # for v4.12 and up
Signed-off-by: Mauro Carvalho Chehab <[email protected]>

drivers/media/v4l2-core/v4l2-ioctl.c

@@ -287,6 +287,7 @@ static void v4l_print_format(const void *arg, bool write_only)
 	const struct v4l2_window *win;
 	const struct v4l2_sdr_format *sdr;
 	const struct v4l2_meta_format *meta;
+	u32 planes;
 	unsigned i;
 
 	pr_cont("type=%s", prt_names(p->type, v4l2_type_names));
@@ -317,7 +318,8 @@ static void v4l_print_format(const void *arg, bool write_only)
 			prt_names(mp->field, v4l2_field_names),
 			mp->colorspace, mp->num_planes, mp->flags,
 			mp->ycbcr_enc, mp->quantization, mp->xfer_func);
-		for (i = 0; i < mp->num_planes; i++)
+		planes = min_t(u32, mp->num_planes, VIDEO_MAX_PLANES);
+		for (i = 0; i < planes; i++)
 			printk(KERN_DEBUG "plane %u: bytesperline=%u sizeimage=%u\n", i,
 					mp->plane_fmt[i].bytesperline,
 					mp->plane_fmt[i].sizeimage);