static ssize_t ucma_migrate_id(struct ucma_file *new_file,
			       const char __user *inbuf,
			       int in_len, int out_len)
{
	struct rdma_ucm_migrate_id cmd;
	struct rdma_ucm_migrate_resp resp;
	struct ucma_context *ctx;
	struct fd f;
	struct ucma_file *cur_file;
	int ret = 0;

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

	/* Get current fd to protect against it being closed */
	f = fdget(cmd.fd);
	if (!f.file)
		return -ENOENT;

	/* Validate current fd and prevent destruction of id. */
	ctx = ucma_get_ctx(f.file->private_data, cmd.id);
	if (IS_ERR(ctx)) {
		ret = PTR_ERR(ctx);
		goto file_put;
	}

	cur_file = ctx->file;
	if (cur_file == new_file) {
		resp.events_reported = ctx->events_reported;
		goto response;
	}

	/*
	 * Migrate events between fd's, maintaining order, and avoiding new
	 * events being added before existing events.
	 */
	ucma_lock_files(cur_file, new_file);
	mutex_lock(&mut);

	list_move_tail(&ctx->list, &new_file->ctx_list);
	ucma_move_events(ctx, new_file);
	ctx->file = new_file;
	resp.events_reported = ctx->events_reported;

	mutex_unlock(&mut);
	ucma_unlock_files(cur_file, new_file);

response:
	if (copy_to_user(u64_to_user_ptr(cmd.response),
			 &resp, sizeof(resp)))
		ret = -EFAULT;

	ucma_put_ctx(ctx);
file_put:
	fdput(f);
	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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.