[v2.6.34-stable 028/213] ax25: fix info leak via msg_name in ax25_recvmsg()

From: Paul Gortmaker
Date: Wed Feb 05 2014 - 16:11:47 EST

From: Mathias Krause <minipli@xxxxxxxxxxxxxx>

This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.

commit ef3313e84acbf349caecae942ab3ab731471f1a1 upstream.

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@xxxxxxxxxxxxxx>
Signed-off-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
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 12c350c63717..d082b6db6b81 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -1655,6 +1655,7 @@ 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;

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