netrom: fix info leak via msg_name in nr_recvmsg()

[ 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@googlemail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/netrom/af_netrom.c b/net/netrom/af_netrom.c
index 7261eb81974ff9f3761976372c9272db04a62abd..14c106b49e990e89d81083177a72cdc2029dd06a 100644 (file)
--- a/net/netrom/af_netrom.c
+++ b/net/netrom/af_netrom.c
@@ -1177,6 +1177,7 @@ static int nr_recvmsg(struct kiocb *iocb, struct socket *sock,
        }
 
        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);