ax25: fix info leak via msg_name in ax25_recvmsg()

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@linux-mips.org>
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index 7b11f8bc5071cba0de51054913fa5f3e8bb3f063..e277e38f736b93a133a6cd43cc7b264acfbad641 100644 (file)
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -1642,6 +1642,7 @@ 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;