[Precise Quantal CVE-2013-3224] Bluetooth: fix possible info leak in bt_sock_recvmsg()

[Luis Henriques]

From: Mathias Krause <minipli at googlemail.com>

CVE-2013-3224

BugLink: https://bugs.launchpad.net/bugs/1172368

In case the socket is already shutting down, bt_sock_recvmsg() returns
with 0 without updating msg_namelen leading to net/socket.c leaking the
local, uninitialized sockaddr_storage variable to userland -- 128 bytes
of kernel stack memory.

Fix this by moving the msg_namelen assignment in front of the shutdown
test.

Cc: Marcel Holtmann <marcel at holtmann.org>
Cc: Gustavo Padovan <gustavo at padovan.org>
Cc: Johan Hedberg <johan.hedberg at gmail.com>
Signed-off-by: Mathias Krause <minipli at googlemail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(cherry picked from commit 4683f42fde3977bdb4e8a09622788cc8b5313778)

Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/bluetooth/af_bluetooth.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.c
index 5355df6..b04795e 100644
--- a/net/bluetooth/af_bluetooth.c
+++ b/net/bluetooth/af_bluetooth.c
@@ -230,6 +230,8 @@ int bt_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 	if (flags & (MSG_OOB))
 		return -EOPNOTSUPP;
 
+	msg->msg_namelen = 0;
+
 	skb = skb_recv_datagram(sk, flags, noblock, &err);
 	if (!skb) {
 		if (sk->sk_shutdown & RCV_SHUTDOWN)
@@ -237,8 +239,6 @@ int bt_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 		return err;
 	}
 
-	msg->msg_namelen = 0;
-
 	copied = skb->len;
 	if (len < copied) {
 		msg->msg_flags |= MSG_TRUNC;
-- 
1.8.1.2