static int check_unshare_flags(unsigned long unshare_flags)
{
	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
				CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
		return -EINVAL;
	/*
	 * Not implemented, but pretend it works if there is nothing
	 * to unshare.  Note that unsharing the address space or the
	 * signal handlers also need to unshare the signal queues (aka
	 * CLONE_THREAD).
	 */
	if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
		if (!thread_group_empty(current))
			return -EINVAL;
	}
	if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
		if (atomic_read(&current->sighand->count) > 1)
			return -EINVAL;
	}
	if (unshare_flags & CLONE_VM) {
		if (!current_is_single_threaded())
			return -EINVAL;
	}

	return 0;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.