static uint32_t ssd0323_transfer(SSISlave *dev, uint32_t data)
{
    ssd0323_state *s = FROM_SSI_SLAVE(ssd0323_state, dev);

    switch (s->mode) {
    case SSD0323_DATA:
        DPRINTF("data 0x%02x\n", data);
        s->framebuffer[s->col + s->row * 64] = data;
        if (s->remap & REMAP_VERTICAL) {
            s->row++;
            if (s->row > s->row_end) {
                s->row = s->row_start;
                s->col++;
            }
            if (s->col > s->col_end) {
                s->col = s->col_start;
            }
        } else {
            s->col++;
            if (s->col > s->col_end) {
                s->row++;
                s->col = s->col_start;
            }
            if (s->row > s->row_end) {
                s->row = s->row_start;
            }
        }
        s->redraw = 1;
        break;
    case SSD0323_CMD:
        DPRINTF("cmd 0x%02x\n", data);
        if (s->cmd_len == 0) {
            s->cmd = data;
        } else {
            s->cmd_data[s->cmd_len - 1] = data;
        }
        s->cmd_len++;
        switch (s->cmd) {
#define DATA(x) if (s->cmd_len <= (x)) return 0
        case 0x15: /* Set column.  */
            DATA(2);
            s->col = s->col_start = s->cmd_data[0] % 64;
            s->col_end = s->cmd_data[1] % 64;
            break;
        case 0x75: /* Set row.  */
            DATA(2);
            s->row = s->row_start = s->cmd_data[0] % 80;
            s->row_end = s->cmd_data[1] % 80;
            break;
        case 0x81: /* Set contrast */
            DATA(1);
            break;
        case 0x84: case 0x85: case 0x86: /* Max current.  */
            DATA(0);
            break;
        case 0xa0: /* Set remapping.  */
            /* FIXME: Implement this.  */
            DATA(1);
            s->remap = s->cmd_data[0];
            break;
        case 0xa1: /* Set display start line.  */
        case 0xa2: /* Set display offset.  */
            /* FIXME: Implement these.  */
            DATA(1);
            break;
        case 0xa4: /* Normal mode.  */
        case 0xa5: /* All on.  */
        case 0xa6: /* All off.  */
        case 0xa7: /* Inverse.  */
            /* FIXME: Implement these.  */
            DATA(0);
            break;
        case 0xa8: /* Set multiplex ratio.  */
        case 0xad: /* Set DC-DC converter.  */
            DATA(1);
            /* Ignored.  Don't care.  */
            break;
        case 0xae: /* Display off.  */
        case 0xaf: /* Display on.  */
            DATA(0);
            /* TODO: Implement power control.  */
            break;
        case 0xb1: /* Set phase length.  */
        case 0xb2: /* Set row period.  */
        case 0xb3: /* Set clock rate.  */
        case 0xbc: /* Set precharge.  */
        case 0xbe: /* Set VCOMH.  */
        case 0xbf: /* Set segment low.  */
            DATA(1);
            /* Ignored.  Don't care.  */
            break;
        case 0xb8: /* Set grey scale table.  */
            /* FIXME: Implement this.  */
            DATA(8);
            break;
        case 0xe3: /* NOP.  */
            DATA(0);
            break;
        case 0xff: /* Nasty hack because we don't handle chip selects
                      properly.  */
            break;
        default:
            BADF("Unknown command: 0x%x\n", data);
        }
        s->cmd_len = 0;
        return 0;
    }
    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.