[PATCH] llc: Fix missing msg_namelen update in llc_ui_recvmsg()

[Luis Henriques]

From: Mathias Krause <minipli at googlemail.com>

CVE-2013-3231

BugLink: https://bugs.launchpad.net/bugs/1172385

For stream sockets the code misses to update 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. The msg_namelen update is also missing for datagram sockets
in case the socket is shutting down during receive.

Fix both issues by setting msg_namelen to 0 early. It will be
updated later if we're going to fill the msg_name member.

Cc: Arnaldo Carvalho de Melo <acme at ghostprotocols.net>
Signed-off-by: Mathias Krause <minipli at googlemail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(cherry picked from commit c77a4b9cffb6215a15196ec499490d116dfad181)

Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/llc/af_llc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 606b6ad..8a814a5 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -674,6 +674,8 @@ static int llc_ui_recvmsg(struct kiocb *iocb, struct socket *sock,
 	int target;	/* Read at least this many bytes */
 	long timeo;
 
+	msg->msg_namelen = 0;
+
 	lock_sock(sk);
 	copied = -ENOTCONN;
 	if (unlikely(sk->sk_type == SOCK_STREAM && sk->sk_state == TCP_LISTEN))
-- 
1.8.1.2