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From:   Kleber Sacilotto de Souza <kleber.souza@canonical.com>
To:     netdev@vger.kernel.org
Cc:     Gerrit Renker <gerrit@erg.abdn.ac.uk>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Thadeu Lima de Souza Cascardo <cascardo@canonical.com>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        "Alexander A. Klimov" <grandmaster@al2klimov.de>,
        Kees Cook <keescook@chromium.org>,
        Eric Dumazet <edumazet@google.com>,
        Alexey Kodanev <alexey.kodanev@oracle.com>,
        dccp@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2/2] Revert "dccp: don't free ccid2_hc_tx_sock struct in dccp_disconnect()"
Date:   Tue, 13 Oct 2020 19:18:49 +0200
Message-Id: <20201013171849.236025-3-kleber.souza@canonical.com>
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From: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

This reverts commit 2677d20677314101293e6da0094ede7b5526d2b1.

This fixes an issue that after disconnect, dccps_hc_tx_ccid will still be
kept, allowing the socket to be reused as a listener socket, and the cloned
socket will free its dccps_hc_tx_ccid, leading to a later use after free,
when the listener socket is closed.

This addresses CVE-2020-16119.

Fixes: 2677d2067731 (dccp: don't free ccid2_hc_tx_sock struct in dccp_disconnect())
Reported-by: Hadar Manor
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
---
 net/dccp/proto.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 6d705d90c614..359e848dba6c 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -279,7 +279,9 @@ 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 = NULL;
+	dp->dccps_hc_tx_ccid = NULL;
 
 	__skb_queue_purge(&sk->sk_receive_queue);
 	__skb_queue_purge(&sk->sk_write_queue);
-- 
2.25.1