static int __sys_recvmsg(struct socket *sock, struct msghdr __user *msg,
			 struct msghdr *msg_sys, unsigned flags, int nosec)
{
	struct compat_msghdr __user *msg_compat =
	    (struct compat_msghdr __user *)msg;
	struct iovec iovstack[UIO_FASTIOV];
	struct iovec *iov = iovstack;
	unsigned long cmsg_ptr;
	int err, iov_size, total_len, len;

	/* kernel mode address */
	struct sockaddr_storage addr;

	/* user mode address pointers */
	struct sockaddr __user *uaddr;
	int __user *uaddr_len;

	if (MSG_CMSG_COMPAT & flags) {
		if (get_compat_msghdr(msg_sys, msg_compat))
			return -EFAULT;
	} else if (copy_from_user(msg_sys, msg, sizeof(struct msghdr)))
		return -EFAULT;

	err = -EMSGSIZE;
	if (msg_sys->msg_iovlen > UIO_MAXIOV)
		goto out;

	/* Check whether to allocate the iovec area */
	err = -ENOMEM;
	iov_size = msg_sys->msg_iovlen * sizeof(struct iovec);
	if (msg_sys->msg_iovlen > UIO_FASTIOV) {
		iov = sock_kmalloc(sock->sk, iov_size, GFP_KERNEL);
		if (!iov)
			goto out;
	}

	/*
	 *      Save the user-mode address (verify_iovec will change the
	 *      kernel msghdr to use the kernel address space)
	 */

	uaddr = (__force void __user *)msg_sys->msg_name;
	uaddr_len = COMPAT_NAMELEN(msg);
	if (MSG_CMSG_COMPAT & flags) {
		err = verify_compat_iovec(msg_sys, iov,
					  (struct sockaddr *)&addr,
					  VERIFY_WRITE);
	} else
		err = verify_iovec(msg_sys, iov,
				   (struct sockaddr *)&addr,
				   VERIFY_WRITE);
	if (err < 0)
		goto out_freeiov;
	total_len = err;

	cmsg_ptr = (unsigned long)msg_sys->msg_control;
	msg_sys->msg_flags = flags & (MSG_CMSG_CLOEXEC|MSG_CMSG_COMPAT);

	if (sock->file->f_flags & O_NONBLOCK)
		flags |= MSG_DONTWAIT;
	err = (nosec ? sock_recvmsg_nosec : sock_recvmsg)(sock, msg_sys,
							  total_len, flags);
	if (err < 0)
		goto out_freeiov;
	len = err;

	if (uaddr != NULL) {
		err = move_addr_to_user((struct sockaddr *)&addr,
					msg_sys->msg_namelen, uaddr,
					uaddr_len);
		if (err < 0)
			goto out_freeiov;
	}
	err = __put_user((msg_sys->msg_flags & ~MSG_CMSG_COMPAT),
			 COMPAT_FLAGS(msg));
	if (err)
		goto out_freeiov;
	if (MSG_CMSG_COMPAT & flags)
		err = __put_user((unsigned long)msg_sys->msg_control - cmsg_ptr,
				 &msg_compat->msg_controllen);
	else
		err = __put_user((unsigned long)msg_sys->msg_control - cmsg_ptr,
				 &msg->msg_controllen);
	if (err)
		goto out_freeiov;
	err = len;

out_freeiov:
	if (iov != iovstack)
		sock_kfree_s(sock->sk, iov, iov_size);
out:
	return err;
}

Unknown