dccp: don't duplicate ccid when cloning dccp sock

commit d9ea761fdd197351890418acd462c51f241014a7 upstream.

Commit 2677d2067731 ("dccp: don't free ccid2_hc_tx_sock ...") fixed
a UAF but reintroduced CVE-2017-6074.

When the sock is cloned, two dccps_hc_tx_ccid will reference to the
same ccid. So one can free the ccid object twice from two socks after
cloning.

This issue was found by "Hadar Manor" as well and assigned with
CVE-2020-16119, which was fixed in Ubuntu's kernel. So here I port
the patch from Ubuntu to fix it.

The patch prevents cloned socks from referencing the same ccid.

Fixes: 2677d2067731410 ("dccp: don't free ccid2_hc_tx_sock ...")
Signed-off-by: Zhenpeng Lin <zplin@psu.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index 178bb9833311f83205317b07fe64cb2e45a9f734..f6092536de034f6b0fc48ddab2ebf0fc67690ea9 100644 (file)
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -98,6 +98,8 @@ struct sock *dccp_create_openreq_child(const struct sock *sk,
                newdp->dccps_role           = DCCP_ROLE_SERVER;
                newdp->dccps_hc_rx_ackvec   = NULL;
                newdp->dccps_service_list   = NULL;
+               newdp->dccps_hc_rx_ccid     = NULL;
+               newdp->dccps_hc_tx_ccid     = NULL;
                newdp->dccps_service        = dreq->dreq_service;
                newdp->dccps_timestamp_echo = dreq->dreq_timestamp_echo;
                newdp->dccps_timestamp_time = dreq->dreq_timestamp_time;