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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Mohamed Ghannam <simo.ghannam@gmail.com>,
        Eric Dumazet <edumazet@google.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.9 11/88] dccp: CVE-2017-8824: use-after-free in DCCP code
Date:   Thu, 15 Feb 2018 16:16:38 +0100
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

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

commit 69c64866ce072dea1d1e59a0d61e0f66c0dffb76 upstream.

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>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/dccp/proto.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -259,6 +259,7 @@ int dccp_disconnect(struct sock *sk, int
 {
 	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
 		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);