jbig2_decode_generic_template2(Jbig2Ctx *ctx,
                               Jbig2Segment *segment,
                               const Jbig2GenericRegionParams *params, Jbig2ArithState *as, Jbig2Image *image, Jbig2ArithCx *GB_stats)
{
    const int GBW = image->width;
    const int GBH = image->height;
    const int rowstride = image->stride;
    int x, y;
    byte *gbreg_line = (byte *) image->data;

    /* todo: currently we only handle the nominal gbat location */

#ifdef OUTPUT_PBM
    printf("P4\n%d %d\n", GBW, GBH);
#endif

    if (GBW <= 0)
                return 0;

    for (y = 0; y < GBH; y++) {
        uint32_t CONTEXT;
        uint32_t line_m1;
        uint32_t line_m2;
        int padded_width = (GBW + 7) & -8;

        line_m1 = (y >= 1) ? gbreg_line[-rowstride] : 0;
        line_m2 = (y >= 2) ? gbreg_line[-(rowstride << 1)] << 4 : 0;
                                        CONTEXT = ((line_m1 >> 3) & 0x7c) | ((line_m2 >> 3) & 0x380);

        /* 6.2.5.7 3d */
        for (x = 0; x < padded_width; x += 8) {
            byte result = 0;
            int x_minor;
            int minor_width = GBW - x > 8 ? 8 : GBW - x;

            if (y >= 1)
                line_m1 = (line_m1 << 8) | (x + 8 < GBW ? gbreg_line[-rowstride + (x >> 3) + 1] : 0);

            if (y >= 2)
                line_m2 = (line_m2 << 8) | (x + 8 < GBW ? gbreg_line[-(rowstride << 1) + (x >> 3) + 1] << 4 : 0);

                       /* This is the speed-critical inner loop. */
            for (x_minor = 0; x_minor < minor_width; x_minor++) {
                bool bit;

                bit = jbig2_arith_decode(as, &GB_stats[CONTEXT]);
                if (bit < 0)
                            return -1;
                result |= bit << (7 - x_minor);
                CONTEXT = ((CONTEXT & 0x1bd) << 1) | bit | ((line_m1 >> (10 - x_minor)) & 0x4) | ((line_m2 >> (10 - x_minor)) & 0x80);
            }
            gbreg_line[x >> 3] = result;
        }
#ifdef OUTPUT_PBM
        fwrite(gbreg_line, 1, rowstride, stdout);
#endif
        gbreg_line += rowstride;
    }

    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.