[PATCH] netrom: fix info leak via getsockname()

The following patch fixes a 3 bytes info leak via getsockname() on
AF_NETROM socket.

Details:

typedef struct {
	char		ax25_call[7];	/* 6 call + SSID (shifted ascii!) */
} ax25_address;

struct sockaddr_ax25 {
	__kernel_sa_family_t sax25_family;
	ax25_address	sax25_call;
	int		sax25_ndigis;
	/* Digipeater ax25_address sets follow */
};

After compilation, gcc will add 3 padding bytes after sax25_call to
align sax25_ndigis and nr_getname does not clear these padding bytes
before returning to userland, poc attached.

Signed-off-by: Clement Lecigne <redacted>

--- a/net/netrom/af_netrom.c
+++ b/net/netrom/af_netrom.c

@@ -838,6 +838,8 @@ static int nr_getname(struct socket *sock, struct

sockaddr *uaddr,
        struct sock *sk = sock->sk;
        struct nr_sock *nr = nr_sk(sk);

+    memset(sax, 0, sizeof(struct sockaddr_ax25));
+
        lock_sock(sk);
        if (peer != 0) {
                if (sk->sk_state != TCP_ESTABLISHED) {