Code: int vcc_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
		size_t size, int flags)
{
	struct sock *sk = sock->sk;
	struct atm_vcc *vcc;
 	struct sk_buff *skb;
 	int copied, error = -EINVAL;
 
 	if (sock->state != SS_CONNECTED)
 		return -ENOTCONN;
 
	/* only handle MSG_DONTWAIT and MSG_PEEK */
	if (flags & ~(MSG_DONTWAIT | MSG_PEEK))
		return -EOPNOTSUPP;

	vcc = ATM_SD(sock);
	if (test_bit(ATM_VF_RELEASED, &vcc->flags) ||
	    test_bit(ATM_VF_CLOSE, &vcc->flags) ||
	    !test_bit(ATM_VF_READY, &vcc->flags))
		return 0;

	skb = skb_recv_datagram(sk, flags, flags & MSG_DONTWAIT, &error);
	if (!skb)
		return error;

	copied = skb->len;
	if (copied > size) {
		copied = size;
		msg->msg_flags |= MSG_TRUNC;
	}

	error = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
	if (error)
		return error;
	sock_recv_ts_and_drops(msg, sk, skb);

	if (!(flags & MSG_PEEK)) {
		pr_debug("%d -= %d\n", atomic_read(&sk->sk_rmem_alloc),
			 skb->truesize);
		atm_return(vcc, skb->truesize);
	}

	skb_free_datagram(sk, skb);
	return copied;
}

Vulnerability Type: +Info 
CWE ID: CWE-200
Summary: The vcc_recvmsg function in net/atm/common.c in the Linux kernel before 3.9-rc7 does not initialize a certain length variable, which allows local users to obtain sensitive information from kernel stack memory via a crafted recvmsg or recvfrom system call.
Commit Message: atm: update msg_namelen in vcc_recvmsg()

The current code does not fill the msg_name member in case it is set.
It also does not set the msg_namelen member to 0 and therefore makes
net/socket.c leak the local, uninitialized sockaddr_storage variable
to userland -- 128 bytes of kernel stack memory.

Fix that by simply setting msg_namelen to 0 as obviously nobody cared
about vcc_recvmsg() not filling the msg_name in case it was set.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>