static ssize_t ucma_join_ip_multicast(struct ucma_file *file,
				      const char __user *inbuf,
				      int in_len, int out_len)
{
	struct rdma_ucm_join_ip_mcast cmd;
	struct rdma_ucm_join_mcast join_cmd;

	if (copy_from_user(&cmd, inbuf, sizeof(cmd)))
		return -EFAULT;

	join_cmd.response = cmd.response;
	join_cmd.uid = cmd.uid;
	join_cmd.id = cmd.id;
	join_cmd.addr_size = rdma_addr_size_in6(&cmd.addr);
	if (!join_cmd.addr_size)
		return -EINVAL;

	join_cmd.join_flags = RDMA_MC_JOIN_FLAG_FULLMEMBER;
	memcpy(&join_cmd.addr, &cmd.addr, join_cmd.addr_size);

	return ucma_process_join(file, &join_cmd, out_len);
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.