static void vmsvga_text_update(void *opaque, console_ch_t *chardata)
{
    struct vmsvga_state_s *s = opaque;

    if (s->vga.hw_ops->text_update) {
        s->vga.hw_ops->text_update(&s->vga, chardata);
    }
}

The product writes data past the end, or before the beginning, of the intended buffer.