fix CVE-2017-6074 DCCP double-free vulnerability

dccp-fix-freeing-skb-too-early-for-IPV6_RECVPKTINFO.patch

@@ -0,0 +1,47 @@
+From 5edabca9d4cff7f1f2b68f0bac55ef99d9798ba4 Mon Sep 17 00:00:00 2001
+From: Andrey Konovalov <andreyknvl@google.com>
+Date: Thu, 16 Feb 2017 17:22:46 +0100
+Subject: dccp: fix freeing skb too early for IPV6_RECVPKTINFO
+
+In the current DCCP implementation an skb for a DCCP_PKT_REQUEST packet
+is forcibly freed via __kfree_skb in dccp_rcv_state_process if
+dccp_v6_conn_request successfully returns.
+
+However, if IPV6_RECVPKTINFO is set on a socket, the address of the skb
+is saved to ireq->pktopts and the ref count for skb is incremented in
+dccp_v6_conn_request, so skb is still in use. Nevertheless, it gets freed
+in dccp_rcv_state_process.
+
+Fix by calling consume_skb instead of doing goto discard and therefore
+calling __kfree_skb.
+
+Similar fixes for TCP:
+
+fb7e2399ec17f1004c0e0ccfd17439f8759ede01 [TCP]: skb is unexpectedly freed.
+0aea76d35c9651d55bbaf746e7914e5f9ae5a25d tcp: SYN packets are now
+simply consumed
+
+Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
+Acked-by: Eric Dumazet <edumazet@google.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+---
+ net/dccp/input.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/net/dccp/input.c b/net/dccp/input.c
+index ba34718..8fedc2d 100644
+--- a/net/dccp/input.c
++++ b/net/dccp/input.c
+@@ -606,7 +606,8 @@ int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
+ 			if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
+ 								    skb) < 0)
+ 				return 1;
+-			goto discard;
++			consume_skb(skb);
++			return 0;
+ 		}
+ 		if (dh->dccph_type == DCCP_PKT_RESET)
+ 			goto discard;
+-- 
+cgit v0.12
+

kernel.spec

@@ -646,6 +646,9 @@ Patch861: w1-ds2490-USB-transfer-buffers-need-to-be-DMAable.patch
 #rhbz 1422969
 Patch862: rt2800-warning.patch
 
+#CVE-2017-6074
+Patch863: dccp-fix-freeing-skb-too-early-for-IPV6_RECVPKTINFO.patch
+
 # END OF PATCH DEFINITIONS
 
 %endif
@@ -2175,6 +2178,9 @@ fi
 #
 # 
 %changelog
+* Wed Feb 22 2017 Justin M. Forbes <jforbes@fedoraproject.org>
+- CVE-2017-6074 DCCP double-free vulnerability
+
 * Mon Feb 20 2017 Laura Abbott <labbott@fedoraproject.org> - 4.9.11-100
 - Linux v4.9.11
 - Fix rt2800 warning (rhbz 1422969)