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

[simo.ghannam@gmail.com]

From: Mohamed Ghannam <simo.ghannam@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.ghannam@gmail.com>
---
 net/dccp/proto.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index b68168f..1814584 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;
 
@@ -279,6 +280,9 @@ int dccp_disconnect(struct sock *sk, int flags)
 
 	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 = dp->dccps_hc_tx_ccid = NULL;
 	__skb_queue_purge(&sk->sk_receive_queue);
 	__skb_queue_purge(&sk->sk_write_queue);
 	if (sk->sk_send_head != NULL) {
-- 
2.7.4