[100/118] Bluetooth: fix possible info leak in bt_sock_recvmsg()

[Ben Hutchings]

3.2.45-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Mathias Krause <minipli@xxxxxxxxxxxxxx>

[ Upstream commit 4683f42fde3977bdb4e8a09622788cc8b5313778 ]

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@xxxxxxxxxxxx>
Cc: Gustavo Padovan <gustavo@xxxxxxxxxxx>
Cc: Johan Hedberg <johan.hedberg@xxxxxxxxx>
Signed-off-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 net/bluetooth/af_bluetooth.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/bluetooth/af_bluetooth.c
+++ b/net/bluetooth/af_bluetooth.c
@@ -245,6 +245,8 @@ int bt_sock_recvmsg(struct kiocb *iocb,
 	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)
@@ -252,8 +254,6 @@ int bt_sock_recvmsg(struct kiocb *iocb,
 		return err;
 	}
 
-	msg->msg_namelen = 0;
-
 	copied = skb->len;
 	if (len < copied) {
 		msg->msg_flags |= MSG_TRUNC;

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