From: Ben Hutchings <ben@decadent.org.uk>
Date: Thu, 30 Oct 2014 18:27:17 +0000 (+0000)
Subject: drivers/net, ipv6: Select IPv6 fragment idents for virtio UFO packets
X-Git-Tag: v3.16.35~3409
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=bdaa127644ae8d79c8bbe2c2a2800cebd1806546;p=thirdparty%2Fkernel%2Fstable.git

drivers/net, ipv6: Select IPv6 fragment idents for virtio UFO packets

commit 5188cd44c55db3e92cd9e77a40b5baa7ed4340f7 upstream.

UFO is now disabled on all drivers that work with virtio net headers,
but userland may try to send UFO/IPv6 packets anyway.  Instead of
sending with ID=0, we should select identifiers on their behalf (as we
used to).

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Fixes: 916e4cf46d02 ("ipv6: reuse ip6_frag_id from ip6_ufo_append_data")
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index ff1acf99c10b9..07c942b6ae011 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -16,6 +16,7 @@
 #include <linux/idr.h>
 #include <linux/fs.h>
 
+#include <net/ipv6.h>
 #include <net/net_namespace.h>
 #include <net/rtnetlink.h>
 #include <net/sock.h>
@@ -570,6 +571,8 @@ static int macvtap_skb_from_vnet_hdr(struct sk_buff *skb,
 			break;
 		case VIRTIO_NET_HDR_GSO_UDP:
 			gso_type = SKB_GSO_UDP;
+			if (skb->protocol == htons(ETH_P_IPV6))
+				ipv6_proxy_select_ident(skb);
 			break;
 		default:
 			return -EINVAL;
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 6c48ae7b1faa8..ee7538dc9c213 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -65,6 +65,7 @@
 #include <linux/nsproxy.h>
 #include <linux/virtio_net.h>
 #include <linux/rcupdate.h>
+#include <net/ipv6.h>
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>
 #include <net/rtnetlink.h>
@@ -1139,6 +1140,8 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 		break;
 	}
 
+	skb_reset_network_header(skb);
+
 	if (gso.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
 		pr_debug("GSO!\n");
 		switch (gso.gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
@@ -1150,6 +1153,8 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 			break;
 		case VIRTIO_NET_HDR_GSO_UDP:
 			skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
+			if (skb->protocol == htons(ETH_P_IPV6))
+				ipv6_proxy_select_ident(skb);
 			break;
 		default:
 			tun->dev->stats.rx_frame_errors++;
@@ -1179,7 +1184,6 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 		skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
 	}
 
-	skb_reset_network_header(skb);
 	skb_probe_transport_header(skb, 0);
 
 	rxhash = skb_get_hash(skb);
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 574337fe72ddb..9b442a8d68ba3 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -668,6 +668,8 @@ static inline int ipv6_addr_diff(const struct in6_addr *a1, const struct in6_add
 	return __ipv6_addr_diff(a1, a2, sizeof(struct in6_addr));
 }
 
+void ipv6_proxy_select_ident(struct sk_buff *skb);
+
 int ip6_dst_hoplimit(struct dst_entry *dst);
 
 static inline int ip6_sk_dst_hoplimit(struct ipv6_pinfo *np, struct flowi6 *fl6,
diff --git a/net/ipv6/output_core.c b/net/ipv6/output_core.c
index 5ec867e4a8b74..1d4156ddf355a 100644
--- a/net/ipv6/output_core.c
+++ b/net/ipv6/output_core.c
@@ -3,11 +3,45 @@
  * not configured or static.  These functions are needed by GSO/GRO implementation.
  */
 #include <linux/export.h>
+#include <net/ip.h>
 #include <net/ipv6.h>
 #include <net/ip6_fib.h>
 #include <net/addrconf.h>
 #include <net/secure_seq.h>
 
+/* This function exists only for tap drivers that must support broken
+ * clients requesting UFO without specifying an IPv6 fragment ID.
+ *
+ * This is similar to ipv6_select_ident() but we use an independent hash
+ * seed to limit information leakage.
+ *
+ * The network header must be set before calling this.
+ */
+void ipv6_proxy_select_ident(struct sk_buff *skb)
+{
+	static u32 ip6_proxy_idents_hashrnd __read_mostly;
+	struct in6_addr buf[2];
+	struct in6_addr *addrs;
+	u32 hash, id;
+
+	addrs = skb_header_pointer(skb,
+				   skb_network_offset(skb) +
+				   offsetof(struct ipv6hdr, saddr),
+				   sizeof(buf), buf);
+	if (!addrs)
+		return;
+
+	net_get_random_once(&ip6_proxy_idents_hashrnd,
+			    sizeof(ip6_proxy_idents_hashrnd));
+
+	hash = __ipv6_addr_jhash(&addrs[1], ip6_proxy_idents_hashrnd);
+	hash = __ipv6_addr_jhash(&addrs[0], hash);
+
+	id = ip_idents_reserve(hash, 1);
+	skb_shinfo(skb)->ip6_frag_id = htonl(id);
+}
+EXPORT_SYMBOL_GPL(ipv6_proxy_select_ident);
+
 int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
 {
 	u16 offset = sizeof(struct ipv6hdr);