static ssize_t nfs_idmap_get_desc(const char *name, size_t namelen,
				const char *type, size_t typelen, char **desc)
{
	char *cp;
	size_t desclen = typelen + namelen + 2;

	*desc = kmalloc(desclen, GFP_KERNEL);
	if (!*desc)
		return -ENOMEM;

	cp = *desc;
	memcpy(cp, type, typelen);
	cp += typelen;
	*cp++ = ':';

	memcpy(cp, name, namelen);
	cp += namelen;
	*cp = '\0';
	return desclen;
}

The product dereferences a pointer that it expects to be valid but is NULL.