[SRU][T/X/Z/A][PATCH 1/1] dccp: CVE-2017-8824: use-after-free in DCCP code

[Kleber Sacilotto de Souza]

From: Mohamed Ghannam <simo.ghannam at 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 at gmail.com>
Reviewed-by: Eric Dumazet <edumazet at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>

CVE-2017-8824
(cherry picked from commit 69c64866ce072dea1d1e59a0d61e0f66c0dffb76 linux-next)
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
---
 net/dccp/proto.c | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'net/dccp/proto.c')

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);
-- 
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