static ssize_t ucma_write(struct file *filp, const char __user *buf,
			  size_t len, loff_t *pos)
{
	struct ucma_file *file = filp->private_data;
	struct rdma_ucm_cmd_hdr hdr;
	ssize_t ret;

	if (!ib_safe_file_access(filp)) {
		pr_err_once("ucma_write: process %d (%s) changed security contexts after opening file descriptor, this is not allowed.\n",
			    task_tgid_vnr(current), current->comm);
		return -EACCES;
	}

	if (len < sizeof(hdr))
		return -EINVAL;

	if (copy_from_user(&hdr, buf, sizeof(hdr)))
		return -EFAULT;

	if (hdr.cmd >= ARRAY_SIZE(ucma_cmd_table))
		return -EINVAL;

	if (hdr.in + sizeof(hdr) > len)
		return -EINVAL;

	if (!ucma_cmd_table[hdr.cmd])
		return -ENOSYS;

	ret = ucma_cmd_table[hdr.cmd](file, buf + sizeof(hdr), hdr.in, hdr.out);
	if (!ret)
		ret = len;

	return ret;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.