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: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 3d604e1349c0b0e5d94ff755a90c7dd395b92a24..4caf63f0ef052caff83110f475422875df4d3cbd 100644 (file)
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -532,6 +532,7 @@ 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;