[Lucid Precise Quantal CVE-2013-3223] ax25: fix info leak via msg_name in ax25_recvmsg()

[Luis Henriques]

From: Mathias Krause <minipli at googlemail.com>

CVE-2013-3223

BugLink: https://bugs.launchpad.net/bugs/1172366

When msg_namelen is non-zero the sockaddr info gets filled out, as
requested, but the code fails to initialize the padding bytes of struct
sockaddr_ax25 inserted by the compiler for alignment. Additionally the
msg_namelen value is updated to sizeof(struct full_sockaddr_ax25) but is
not always filled up to this size.

Both issues lead to the fact that the code will leak uninitialized
kernel stack bytes in net/socket.c.

Fix both issues by initializing the memory with memset(0).

Cc: Ralf Baechle <ralf at linux-mips.org>
Signed-off-by: Mathias Krause <minipli at googlemail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(cherry picked from commit ef3313e84acbf349caecae942ab3ab731471f1a1)

Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/ax25/af_ax25.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index 779095d..d53a123 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -1647,6 +1647,7 @@ static int ax25_recvmsg(struct kiocb *iocb, struct socket *sock,
 		ax25_address src;
 		const unsigned char *mac = skb_mac_header(skb);
 
+		memset(sax, 0, sizeof(struct full_sockaddr_ax25));
 		ax25_addr_parse(mac + 1, skb->data - mac - 1, &src, NULL,
 				&digi, NULL, NULL);
 		sax->sax25_family = AF_AX25;
-- 
1.8.1.2