[ 13/34] netrom: fix info leak via msg_name in nr_recvmsg()

[Greg Kroah-Hartman]

3.4-stable review patch.  If anyone has any objections, please let me know.

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


From: Mathias Krause <minipli@xxxxxxxxxxxxxx>

[ Upstream commits 3ce5efad47b62c57a4f5c54248347085a750ce0e and
  c802d759623acbd6e1ee9fbdabae89159a513913 ]

In case msg_name is set 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. Also
the sax25_ndigis member does not get assigned, leaking four more
bytes.

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).

Signed-off-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/netrom/af_netrom.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/netrom/af_netrom.c
+++ b/net/netrom/af_netrom.c
@@ -1177,6 +1177,7 @@ static int nr_recvmsg(struct kiocb *iocb
 	}
 
 	if (sax != NULL) {
+		memset(sax, 0, sizeof(sax));
 		sax->sax25_family = AF_NETROM;
 		skb_copy_from_linear_data_offset(skb, 7, sax->sax25_call.ax25_call,
 			      AX25_ADDR_LEN);


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