llc: Fix missing msg_namelen update in llc_ui_recvmsg()

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

1 files changed, 2 insertions, 0 deletions

diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 88709882c464..48aaa89253e0 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -720,6 +720,8 @@ 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))