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

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

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

On Thu, May 09, 2013 at 11:01:48AM +0100, Luis Henriques wrote:
> From: Mathias Krause <minipli@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@linux-mips.org>
> Signed-off-by: Mathias Krause <minipli@googlemail.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> (cherry picked from commit ef3313e84acbf349caecae942ab3ab731471f1a1)
> 
> Signed-off-by: Luis Henriques <luis.henriques@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;

Clean cherry-pick, seems to do what is claimed.

Acked-by: Andy Whitcroft <apw@canonical.com>

-apw