avcodec/lagarith: fix chroma plane width & height

Fixes out of array read
Fixes: asan_heap-oob_1bf48fa_2513_lag-yuy2.avi
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/lagarith.c

@@ -675,10 +675,10 @@ static int lag_decode_frame(AVCodecContext *avctx,
         lag_decode_arith_plane(l, p->data[0], avctx->width, avctx->height,
                                p->linesize[0], buf + offset_ry,
                                buf_size - offset_ry);
-        lag_decode_arith_plane(l, p->data[1], avctx->width / 2,
+        lag_decode_arith_plane(l, p->data[1], (avctx->width + 1) / 2,
                                avctx->height, p->linesize[1],
                                buf + offset_gu, buf_size - offset_gu);
-        lag_decode_arith_plane(l, p->data[2], avctx->width / 2,
+        lag_decode_arith_plane(l, p->data[2], (avctx->width + 1) / 2,
                                avctx->height, p->linesize[2],
                                buf + offset_bv, buf_size - offset_bv);
         break;
@@ -702,11 +702,11 @@ static int lag_decode_frame(AVCodecContext *avctx,
         lag_decode_arith_plane(l, p->data[0], avctx->width, avctx->height,
                                p->linesize[0], buf + offset_ry,
                                buf_size - offset_ry);
-        lag_decode_arith_plane(l, p->data[2], avctx->width / 2,
-                               avctx->height / 2, p->linesize[2],
+        lag_decode_arith_plane(l, p->data[2], (avctx->width + 1) / 2,
+                               (avctx->height + 1) / 2, p->linesize[2],
                                buf + offset_gu, buf_size - offset_gu);
-        lag_decode_arith_plane(l, p->data[1], avctx->width / 2,
-                               avctx->height / 2, p->linesize[1],
+        lag_decode_arith_plane(l, p->data[1], (avctx->width + 1) / 2,
+                               (avctx->height + 1) / 2, p->linesize[1],
                                buf + offset_bv, buf_size - offset_bv);
         break;
     default: