static ssize_t fuse_dev_do_write(struct fuse_dev *fud,
				 struct fuse_copy_state *cs, size_t nbytes)
{
	int err;
	struct fuse_conn *fc = fud->fc;
	struct fuse_pqueue *fpq = &fud->pq;
	struct fuse_req *req;
	struct fuse_out_header oh;

	if (nbytes < sizeof(struct fuse_out_header))
		return -EINVAL;

	err = fuse_copy_one(cs, &oh, sizeof(oh));
	if (err)
		goto err_finish;

	err = -EINVAL;
	if (oh.len != nbytes)
		goto err_finish;

	/*
	 * Zero oh.unique indicates unsolicited notification message
	 * and error contains notification code.
	 */
	if (!oh.unique) {
		err = fuse_notify(fc, oh.error, nbytes - sizeof(oh), cs);
		return err ? err : nbytes;
	}

	err = -EINVAL;
	if (oh.error <= -1000 || oh.error > 0)
		goto err_finish;

	spin_lock(&fpq->lock);
	err = -ENOENT;
	if (!fpq->connected)
		goto err_unlock_pq;

	req = request_find(fpq, oh.unique & ~FUSE_INT_REQ_BIT);
	if (!req)
		goto err_unlock_pq;

	/* Is it an interrupt reply ID? */
	if (oh.unique & FUSE_INT_REQ_BIT) {
		__fuse_get_request(req);
		spin_unlock(&fpq->lock);

		err = -EINVAL;
		if (nbytes != sizeof(struct fuse_out_header)) {
			fuse_put_request(fc, req);
			goto err_finish;
		}

		if (oh.error == -ENOSYS)
			fc->no_interrupt = 1;
		else if (oh.error == -EAGAIN)
			queue_interrupt(&fc->iq, req);
		fuse_put_request(fc, req);

		fuse_copy_finish(cs);
		return nbytes;
	}

	clear_bit(FR_SENT, &req->flags);
	list_move(&req->list, &fpq->io);
	req->out.h = oh;
	set_bit(FR_LOCKED, &req->flags);
	spin_unlock(&fpq->lock);
	cs->req = req;
	if (!req->out.page_replace)
		cs->move_pages = 0;

	err = copy_out_args(cs, &req->out, nbytes);
	fuse_copy_finish(cs);

	spin_lock(&fpq->lock);
	clear_bit(FR_LOCKED, &req->flags);
	if (!fpq->connected)
		err = -ENOENT;
	else if (err)
		req->out.h.error = -EIO;
	if (!test_bit(FR_PRIVATE, &req->flags))
		list_del_init(&req->list);
	spin_unlock(&fpq->lock);

	request_end(fc, req);

	return err ? err : nbytes;

 err_unlock_pq:
	spin_unlock(&fpq->lock);
 err_finish:
	fuse_copy_finish(cs);
	return err;
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.