void intra_predict(VP8Context *s, VP8ThreadData *td, uint8_t *dst[3],
                   VP8Macroblock *mb, int mb_x, int mb_y, int is_vp7)
{
    int x, y, mode, nnz;
    uint32_t tr;

    /* for the first row, we need to run xchg_mb_border to init the top edge
     * to 127 otherwise, skip it if we aren't going to deblock */
    if (mb_y && (s->deblock_filter || !mb_y) && td->thread_nr == 0)
        xchg_mb_border(s->top_border[mb_x + 1], dst[0], dst[1], dst[2],
                       s->linesize, s->uvlinesize, mb_x, mb_y, s->mb_width,
                       s->filter.simple, 1);

    if (mb->mode < MODE_I4x4) {
        mode = check_intra_pred8x8_mode_emuedge(mb->mode, mb_x, mb_y, is_vp7);
        s->hpc.pred16x16[mode](dst[0], s->linesize);
    } else {
        uint8_t *ptr = dst[0];
        uint8_t *intra4x4 = mb->intra4x4_pred_mode_mb;
        const uint8_t lo = is_vp7 ? 128 : 127;
        const uint8_t hi = is_vp7 ? 128 : 129;
        uint8_t tr_top[4] = { lo, lo, lo, lo };

        uint8_t *tr_right = ptr - s->linesize + 16;

        if (mb_y && mb_x == s->mb_width - 1) {
            tr       = tr_right[-1] * 0x01010101u;
            tr_right = (uint8_t *) &tr;
        }

        if (mb->skip)
            AV_ZERO128(td->non_zero_count_cache);

        for (y = 0; y < 4; y++) {
            uint8_t *topright = ptr + 4 - s->linesize;
            for (x = 0; x < 4; x++) {
                int copy = 0;
                ptrdiff_t linesize = s->linesize;
                uint8_t *dst = ptr + 4 * x;
                LOCAL_ALIGNED(4, uint8_t, copy_dst, [5 * 8]);

                if ((y == 0 || x == 3) && mb_y == 0) {
                    topright = tr_top;
                } else if (x == 3)
                    topright = tr_right;

                mode = check_intra_pred4x4_mode_emuedge(intra4x4[x], mb_x + x,
                                                        mb_y + y, &copy, is_vp7);
                if (copy) {
                    dst      = copy_dst + 12;
                    linesize = 8;
                    if (!(mb_y + y)) {
                        copy_dst[3] = lo;
                        AV_WN32A(copy_dst + 4, lo * 0x01010101U);
                    } else {
                        AV_COPY32(copy_dst + 4, ptr + 4 * x - s->linesize);
                        if (!(mb_x + x)) {
                            copy_dst[3] = hi;
                        } else {
                            copy_dst[3] = ptr[4 * x - s->linesize - 1];
                        }
                    }
                    if (!(mb_x + x)) {
                        copy_dst[11] =
                        copy_dst[19] =
                        copy_dst[27] =
                        copy_dst[35] = hi;
                    } else {
                        copy_dst[11] = ptr[4 * x                   - 1];
                        copy_dst[19] = ptr[4 * x + s->linesize     - 1];
                        copy_dst[27] = ptr[4 * x + s->linesize * 2 - 1];
                        copy_dst[35] = ptr[4 * x + s->linesize * 3 - 1];
                    }
                }
                s->hpc.pred4x4[mode](dst, topright, linesize);
                if (copy) {
                    AV_COPY32(ptr + 4 * x,                   copy_dst + 12);
                    AV_COPY32(ptr + 4 * x + s->linesize,     copy_dst + 20);
                    AV_COPY32(ptr + 4 * x + s->linesize * 2, copy_dst + 28);
                    AV_COPY32(ptr + 4 * x + s->linesize * 3, copy_dst + 36);
                }

                nnz = td->non_zero_count_cache[y][x];
                if (nnz) {
                    if (nnz == 1)
                        s->vp8dsp.vp8_idct_dc_add(ptr + 4 * x,
                                                  td->block[y][x], s->linesize);
                    else
                        s->vp8dsp.vp8_idct_add(ptr + 4 * x,
                                               td->block[y][x], s->linesize);
                }
                topright += 4;
            }

            ptr      += 4 * s->linesize;
            intra4x4 += 4;
        }
    }

    mode = check_intra_pred8x8_mode_emuedge(mb->chroma_pred_mode,
                                            mb_x, mb_y, is_vp7);
    s->hpc.pred8x8[mode](dst[1], s->uvlinesize);
    s->hpc.pred8x8[mode](dst[2], s->uvlinesize);

    if (mb_y && (s->deblock_filter || !mb_y) && td->thread_nr == 0)
        xchg_mb_border(s->top_border[mb_x + 1], dst[0], dst[1], dst[2],
                       s->linesize, s->uvlinesize, mb_x, mb_y, s->mb_width,
                       s->filter.simple, 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.