static ssize_t oz_cdev_write(struct file *filp, const char __user *buf,
		size_t count, loff_t *fpos)
{
	struct oz_pd *pd;
	struct oz_elt_buf *eb;
	struct oz_elt_info *ei;
	struct oz_elt *elt;
 	struct oz_app_hdr *app_hdr;
 	struct oz_serial_ctx *ctx;
 
	if (count > sizeof(ei->data) - sizeof(*elt) - sizeof(*app_hdr))
		return -EINVAL;

 	spin_lock_bh(&g_cdev.lock);
 	pd = g_cdev.active_pd;
 	if (pd)
		oz_pd_get(pd);
	spin_unlock_bh(&g_cdev.lock);
	if (pd == NULL)
		return -ENXIO;
	if (!(pd->state & OZ_PD_S_CONNECTED))
		return -EAGAIN;
	eb = &pd->elt_buff;
	ei = oz_elt_info_alloc(eb);
	if (ei == NULL) {
		count = 0;
		goto out;
	}
	elt = (struct oz_elt *)ei->data;
	app_hdr = (struct oz_app_hdr *)(elt+1);
	elt->length = sizeof(struct oz_app_hdr) + count;
	elt->type = OZ_ELT_APP_DATA;
	ei->app_id = OZ_APPID_SERIAL;
	ei->length = elt->length + sizeof(struct oz_elt);
	app_hdr->app_id = OZ_APPID_SERIAL;
	if (copy_from_user(app_hdr+1, buf, count))
		goto out;
	spin_lock_bh(&pd->app_lock[OZ_APPID_USB-1]);
	ctx = (struct oz_serial_ctx *)pd->app_ctx[OZ_APPID_SERIAL-1];
	if (ctx) {
		app_hdr->elt_seq_num = ctx->tx_seq_num++;
		if (ctx->tx_seq_num == 0)
			ctx->tx_seq_num = 1;
		spin_lock(&eb->lock);
		if (oz_queue_elt_info(eb, 0, 0, ei) == 0)
			ei = NULL;
		spin_unlock(&eb->lock);
	}
	spin_unlock_bh(&pd->app_lock[OZ_APPID_USB-1]);
out:
	if (ei) {
		count = 0;
		spin_lock_bh(&eb->lock);
		oz_elt_info_free(eb, ei);
		spin_unlock_bh(&eb->lock);
	}
	oz_pd_put(pd);
	return count;
}

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.