dccp: fix info leak via getsockopt(DCCP_SOCKOPT_CCID_TX_INFO)

[ Upstream commit 7b07f8eb75aa3097cdfd4f6eac3da49db787381d ]

The CCID3 code fails to initialize the trailing padding bytes of struct
tfrc_tx_info added for alignment on 64 bit architectures. It that for
potentially leaks four bytes kernel stack via the getsockopt() syscall.
Add an explicit memset(0) before filling the structure to avoid the
info leak.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 8c67bedf85b01a4f45507483f3cc8e2f49e8cf19..ce0d1403b9caff475ab1ae9f76bd1c48c9037381 100644 (file)
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -531,6 +531,7 @@ static int ccid3_hc_tx_getsockopt(struct sock *sk, const int optname, int len,
        case DCCP_SOCKOPT_CCID_TX_INFO:
                if (len < sizeof(tfrc))
                        return -EINVAL;
+               memset(&tfrc, 0, sizeof(tfrc));
                tfrc.tfrctx_x      = hc->tx_x;
                tfrc.tfrctx_x_recv = hc->tx_x_recv;
                tfrc.tfrctx_x_calc = hc->tx_x_calc;