udp: consistently apply ufo or fragmentation

Orabug: 26921303
CVE: CVE-2017-1000112

When iteratively building a UDP datagram with MSG_MORE and that
datagram exceeds MTU, consistently choose UFO or fragmentation.

Once skb_is_gso, always apply ufo. Conversely, once a datagram is
split across multiple skbs, do not consider ufo.

Sendpage already maintains the first invariant, only add the second.
IPv6 does not have a sendpage implementation to modify.

A gso skb must have a partial checksum, do not follow sk_no_check_tx
in udp_send_skb.

Found by syzkaller.

Fixes: e89e9cf539a2 ("[IPv4/IPv6]: UFO Scatter-gather approach")
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 85f1bd9a7b5a79d5baa8bf44af19658f7bf77bfa)
Signed-off-by: Brian Maly <brian.maly@oracle.com>
Conflicts:
	net/ipv4/ip_output.c
	net/ipv6/ip6_output.c
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 54baa75b2b8cdad52b982a221a3591ab52767f30..9ac65bba64f05edb81aba6a5cea74f173efeb4b3 100644 (file)
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -906,10 +906,12 @@ static int __ip_append_data(struct sock *sk,
                csummode = CHECKSUM_PARTIAL;
 
        cork->length += length;
-       if (((length > mtu) || (skb && skb_is_gso(skb))) &&
+       if ((skb && skb_is_gso(skb)) ||
+           ((length > mtu) &&
+           (skb_queue_len(queue) <= 1) &&
            (sk->sk_protocol == IPPROTO_UDP) &&
            (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len &&
-           (sk->sk_type == SOCK_DGRAM) && !sk->sk_no_check_tx) {
+           (sk->sk_type == SOCK_DGRAM) && !sk->sk_no_check_tx)) {
                err = ip_ufo_append_data(sk, queue, getfrag, from, length,
                                         hh_len, fragheaderlen, transhdrlen,
                                         maxfraglen, flags);
@@ -1251,6 +1253,7 @@ ssize_t   ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
 
        cork->length += size;
        if ((size + skb->len > mtu) &&
+           (skb_queue_len(&sk->sk_write_queue) == 1) &&
            (sk->sk_protocol == IPPROTO_UDP) &&
            (rt->dst.dev->features & NETIF_F_UFO)) {
                skb_shinfo(skb)->gso_size = mtu - fragheaderlen;

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 3b9a3452aa533175c1e87b233891054ba8a5a76e..c8ba3eb0d8bbeeabd75e8eb6ff546c1abac69f7f 100644 (file)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -817,7 +817,7 @@ static int udp_send_skb(struct sk_buff *skb, struct flowi4 *fl4)
        if (is_udplite)                                  /*     UDP-Lite      */
                csum = udplite_csum(skb);
 
-       else if (sk->sk_no_check_tx) {   /* UDP csum disabled */
+       else if (sk->sk_no_check_tx && !skb_is_gso(skb)) {   /* UDP csum off */
 
                skb->ip_summed = CHECKSUM_NONE;
                goto send;

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index a5c8290f3505eaf7d79e768227b1fe414273871f..f823403f48d8018eff358e79d83fda5f29a2999c 100644 (file)
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1423,11 +1423,12 @@ emsgsize:
         */
 
        cork->length += length;
-       if (((length > mtu) ||
-            (skb && skb_is_gso(skb))) &&
+       if ((skb && skb_is_gso(skb)) ||
+           ((length > mtu) &&
+           (skb_queue_len(queue) <= 1) &&
            (sk->sk_protocol == IPPROTO_UDP) &&
            (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len &&
-           (sk->sk_type == SOCK_DGRAM) && !udp_get_no_check6_tx(sk)) {
+           (sk->sk_type == SOCK_DGRAM) && !udp_get_no_check6_tx(sk))) {
                err = ip6_ufo_append_data(sk, queue, getfrag, from, length,
                                          hh_len, fragheaderlen,
                                          transhdrlen, mtu, flags, rt);