media: v4l: ioctl: Sanitize num_planes before using it

The linked commit changed s_fmt/try_fmt to fail if num_planes is bogus.
This, however, is against the spec, which mandates drivers
to return a proper num_planes value, without an error.

Replace the num_planes check and instead clamp it to a sane value,
so we still make sure we don't overflow the planes array by accident.

Fixes: 9048b2e1 ("media: v4l: ioctl: Validate num_planes before using it")
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

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

@@ -1017,6 +1017,12 @@ static void v4l_sanitize_format(struct v4l2_format *fmt)
 {
 	unsigned int offset;
 
+	/* Make sure num_planes is not bogus */
+	if (fmt->type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE ||
+	    fmt->type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE)
+		fmt->fmt.pix_mp.num_planes = min_t(u32, fmt->fmt.pix_mp.num_planes,
+					       VIDEO_MAX_PLANES);
+
 	/*
 	 * The v4l2_pix_format structure has been extended with fields that were
 	 * not previously required to be set to zero by applications. The priv
@@ -1553,8 +1559,6 @@ static int v4l_s_fmt(const struct v4l2_ioctl_ops *ops,
 		if (unlikely(!ops->vidioc_s_fmt_vid_cap_mplane))
 			break;
 		CLEAR_AFTER_FIELD(p, fmt.pix_mp.xfer_func);
-		if (p->fmt.pix_mp.num_planes > VIDEO_MAX_PLANES)
-			break;
 		for (i = 0; i < p->fmt.pix_mp.num_planes; i++)
 			CLEAR_AFTER_FIELD(&p->fmt.pix_mp.plane_fmt[i],
 					  bytesperline);
@@ -1586,8 +1590,6 @@ static int v4l_s_fmt(const struct v4l2_ioctl_ops *ops,
 		if (unlikely(!ops->vidioc_s_fmt_vid_out_mplane))
 			break;
 		CLEAR_AFTER_FIELD(p, fmt.pix_mp.xfer_func);
-		if (p->fmt.pix_mp.num_planes > VIDEO_MAX_PLANES)
-			break;
 		for (i = 0; i < p->fmt.pix_mp.num_planes; i++)
 			CLEAR_AFTER_FIELD(&p->fmt.pix_mp.plane_fmt[i],
 					  bytesperline);
@@ -1656,8 +1658,6 @@ static int v4l_try_fmt(const struct v4l2_ioctl_ops *ops,
 		if (unlikely(!ops->vidioc_try_fmt_vid_cap_mplane))
 			break;
 		CLEAR_AFTER_FIELD(p, fmt.pix_mp.xfer_func);
-		if (p->fmt.pix_mp.num_planes > VIDEO_MAX_PLANES)
-			break;
 		for (i = 0; i < p->fmt.pix_mp.num_planes; i++)
 			CLEAR_AFTER_FIELD(&p->fmt.pix_mp.plane_fmt[i],
 					  bytesperline);
@@ -1689,8 +1689,6 @@ static int v4l_try_fmt(const struct v4l2_ioctl_ops *ops,
 		if (unlikely(!ops->vidioc_try_fmt_vid_out_mplane))
 			break;
 		CLEAR_AFTER_FIELD(p, fmt.pix_mp.xfer_func);
-		if (p->fmt.pix_mp.num_planes > VIDEO_MAX_PLANES)
-			break;
 		for (i = 0; i < p->fmt.pix_mp.num_planes; i++)
 			CLEAR_AFTER_FIELD(&p->fmt.pix_mp.plane_fmt[i],
 					  bytesperline);