[media] mtk-vcodec: add index check in decoder vidioc_qbuf

vb2_qbuf will check the buffer index. If a driver overrides
vidioc_qbuf and use the buffer index, the driver needs to check
the index.
Signed-off-by: Wu-Cheng Li <wuchengli@chromium.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/mtk-vcodec/mtk_vcodec_dec.c

@@ -533,6 +533,10 @@ static int vidioc_vdec_qbuf(struct file *file, void *priv,
 	}
 
 	vq = v4l2_m2m_get_vq(ctx->m2m_ctx, buf->type);
+	if (buf->index >= vq->num_buffers) {
+		mtk_v4l2_debug(1, "buffer index %d out of range", buf->index);
+		return -EINVAL;
+	}
 	vb = vq->bufs[buf->index];
 	vb2_v4l2 = container_of(vb, struct vb2_v4l2_buffer, vb2_buf);
 	mtkbuf = container_of(vb2_v4l2, struct mtk_video_dec_buf, vb);