static void cirrus_invalidate_region(CirrusVGAState * s, int off_begin,
				     int off_pitch, int bytesperline,
				     int lines)
{
    int y;
    int off_cur;
    int off_cur_end;

    for (y = 0; y < lines; y++) {
	off_cur = off_begin;
	off_cur_end = (off_cur + bytesperline) & s->cirrus_addr_mask;
        memory_region_set_dirty(&s->vga.vram, off_cur, off_cur_end - off_cur);
	off_begin += off_pitch;
    }
}

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.