llc: fix info leak via getsockname()

The LLC code wrongly returns 0, i.e. "success", when the socket is
zapped. Together with the uninitialized uaddrlen pointer argument from
sys_getsockname this leads to an arbitrary memory leak of up to 128
bytes kernel stack via the getsockname() syscall.

Return an error instead when the socket is zapped to prevent the info
leak. Also remove the unnecessary memset(0). We don't directly write to
the memory pointed by uaddr but memcpy() a local structure at the end of
the function that is properly initialized.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 8c2919ca36f63c6751b612e3008fd8057aba9944..c2190005a11410e2f95141fb841dadc051157a8b 100644 (file)
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -969,14 +969,13 @@ static int llc_ui_getname(struct socket *sock, struct sockaddr *uaddr,
        struct sockaddr_llc sllc;
        struct sock *sk = sock->sk;
        struct llc_sock *llc = llc_sk(sk);
-       int rc = 0;
+       int rc = -EBADF;
 
        memset(&sllc, 0, sizeof(sllc));
        lock_sock(sk);
        if (sock_flag(sk, SOCK_ZAPPED))
                goto out;
        *uaddrlen = sizeof(sllc);
-       memset(uaddr, 0, *uaddrlen);
        if (peer) {
                rc = -ENOTCONN;
                if (sk->sk_state != TCP_ESTABLISHED)