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

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>

1 files changed, 5 insertions, 0 deletions

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index b68168fcc06a..9d43c1f40274 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);