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

[ Upstream commit 5188cd44c55db3e92cd9e77a40b5baa7ed4340f7 ]

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>

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 052d1832d3fbf41304f96075d8dc8b6d23b09b2d..4abd98efdc34f7ce41921833e2011af83de24e7c 100644 (file)
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -17,6 +17,7 @@
 #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>
@@ -566,6 +567,8 @@ 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 10636cbd3807eefd8bf3d13c5eee98be28deb76f..495830a8ee282268fd337a00ca54b5a107bdb359 100644 (file)
--- 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>
@@ -1103,6 +1104,8 @@ 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) {
@@ -1114,6 +1117,8 @@ 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++;
@@ -1143,7 +1148,6 @@ 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_rxhash(skb);

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 6b4956e4408f7ec634d010b31a4a0077d074c8e7..ea97c94fbc7dae6d8ce80853c38a445d6dc995e6 100644 (file)
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -661,6 +661,8 @@ 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));
 }
 
+extern void ipv6_proxy_select_ident(struct sk_buff *skb);
+
 extern int ip6_dst_hoplimit(struct dst_entry *dst);
 
 /*

diff --git a/net/ipv6/output_core.c b/net/ipv6/output_core.c
index 798eb0f7907830615cd10876c8691c534e7ef470..4bd870af05d6261d39dee53178e5d57d52a7eb82 100644 (file)
--- a/net/ipv6/output_core.c
+++ b/net/ipv6/output_core.c
@@ -3,10 +3,48 @@
  * not configured or static.  These functions are needed by GSO/GRO implementation.
  */
 #include <linux/export.h>
+#include <linux/random.h>
+#include <net/ip.h>
 #include <net/ipv6.h>
 #include <net/ip6_fib.h>
 #include <net/addrconf.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;
+       static bool done = false;
+       u32 hash, id;
+
+       addrs = skb_header_pointer(skb,
+                                  skb_network_offset(skb) +
+                                  offsetof(struct ipv6hdr, saddr),
+                                  sizeof(buf), buf);
+       if (!addrs)
+               return;
+
+       if (!done) {
+               get_random_bytes(&ip6_proxy_idents_hashrnd,
+                                sizeof(ip6_proxy_idents_hashrnd));
+               done = true;
+       }
+
+       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)
 {