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 62522b8d2f9715d28ce019aaeaf901875eaceed9..010ff4652908801572bbca127a5340b72d4b3a07 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;