int update_dimensions(VP8Context *s, int width, int height, int is_vp7)
{
    AVCodecContext *avctx = s->avctx;
    int i, ret;

    if (width  != s->avctx->width || ((width+15)/16 != s->mb_width || (height+15)/16 != s->mb_height) && s->macroblocks_base ||
        height != s->avctx->height) {
        vp8_decode_flush_impl(s->avctx, 1);

        ret = ff_set_dimensions(s->avctx, width, height);
        if (ret < 0)
            return ret;
    }

    s->mb_width  = (s->avctx->coded_width  + 15) / 16;
    s->mb_height = (s->avctx->coded_height + 15) / 16;

    s->mb_layout = is_vp7 || avctx->active_thread_type == FF_THREAD_SLICE &&
                   avctx->thread_count > 1;
    if (!s->mb_layout) { // Frame threading and one thread
        s->macroblocks_base       = av_mallocz((s->mb_width + s->mb_height * 2 + 1) *
                                               sizeof(*s->macroblocks));
        s->intra4x4_pred_mode_top = av_mallocz(s->mb_width * 4);
    } else // Sliced threading
        s->macroblocks_base = av_mallocz((s->mb_width + 2) * (s->mb_height + 2) *
                                         sizeof(*s->macroblocks));
    s->top_nnz     = av_mallocz(s->mb_width * sizeof(*s->top_nnz));
    s->top_border  = av_mallocz((s->mb_width + 1) * sizeof(*s->top_border));
    s->thread_data = av_mallocz(MAX_THREADS * sizeof(VP8ThreadData));

    if (!s->macroblocks_base || !s->top_nnz || !s->top_border ||
        !s->thread_data || (!s->intra4x4_pred_mode_top && !s->mb_layout)) {
        free_buffers(s);
        return AVERROR(ENOMEM);
    }

    for (i = 0; i < MAX_THREADS; i++) {
        s->thread_data[i].filter_strength =
            av_mallocz(s->mb_width * sizeof(*s->thread_data[0].filter_strength));
        if (!s->thread_data[i].filter_strength) {
            free_buffers(s);
            return AVERROR(ENOMEM);
        }
#if HAVE_THREADS
        pthread_mutex_init(&s->thread_data[i].lock, NULL);
        pthread_cond_init(&s->thread_data[i].cond, NULL);
#endif
    }

    s->macroblocks = s->macroblocks_base + 1;

    return 0;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.