[PATCH] dccp: CVE-2017-8824: use-after-free in DCCP code

[simo . ghannam]

From: Mohamed Ghannam <simo.ghan...@gmail.com>

        Whenever the sock object is in DCCP_CLOSED state,
        dccp_disconnect() must free dccps_hc_tx_ccid and
        dccps_hc_rx_ccid and set to NULL.

Signed-off-by: Mohamed Ghannam <simo.ghan...@gmail.com>
---
 net/dccp/proto.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index b68168f..9d43c1f 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -259,6 +259,7 @@ int dccp_disconnect(struct sock *sk, int flags)
 {
        struct inet_connection_sock *icsk = inet_csk(sk);
        struct inet_sock *inet = inet_sk(sk);
+       struct dccp_sock *dp = dccp_sk(sk);
        int err = 0;
        const int old_state = sk->sk_state;
 
@@ -278,6 +279,10 @@ int dccp_disconnect(struct sock *sk, int flags)
                sk->sk_err = ECONNRESET;
 
        dccp_clear_xmit_timers(sk);
+       ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
+       ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
+       dp->dccps_hc_rx_ccid = NULL;
+       dp->dccps_hc_tx_ccid = NULL;
 
        __skb_queue_purge(&sk->sk_receive_queue);
        __skb_queue_purge(&sk->sk_write_queue);
-- 
2.7.4