udp: consistently apply ufo or fragmentation

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>
CVE-2017-1000112

(cherry-picked from commit 85f1bd9a7b5a79d5baa8bf44af19658f7bf77bfa)
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 9f6c8631446c26a4bb59f04dad444e9504ac3841..49e9b2bc6e3329b263cb97a16e7ed5869506be6a 100644 (file)
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -958,11 +958,12 @@ static int __ip_append_data(struct sock *sk,
                csummode = CHECKSUM_PARTIAL;
 
        cork->length += length;
-       if ((((length + (skb ? skb->len : fragheaderlen)) > mtu) ||
-            (skb && skb_is_gso(skb))) &&
+       if ((skb && skb_is_gso(skb)) ||
+           (((length + (skb ? skb->len : fragheaderlen)) > mtu) &&
+           (skb_queue_len(queue) <= 1) &&
            (sk->sk_protocol == IPPROTO_UDP) &&
            (rt->dst.dev->features & NETIF_F_UFO) && !dst_xfrm(&rt->dst) &&
-           (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);
@@ -1278,6 +1279,7 @@ ssize_t   ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
                return -EINVAL;
 
        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)) {
                if (skb->ip_summed != CHECKSUM_PARTIAL)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 8aab7d78d25bc6eaa42dcc960cdbd5086f614cad..2d20e23ea42053308dd545429f62fb6117b9f733 100644 (file)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -814,7 +814,7 @@ 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 71c6ee05a42275efdd1f61e74a4bd26cc97efa6d..b65ce893f1cb88eaf7272c40550d9d0c10108ef6 100644 (file)
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1386,11 +1386,12 @@ emsgsize:
         */
 
        cork->length += length;
-       if ((((length + (skb ? skb->len : headersize)) > mtu) ||
-            (skb && skb_is_gso(skb))) &&
+       if ((skb && skb_is_gso(skb)) ||
+           (((length + (skb ? skb->len : headersize)) > mtu) &&
+           (skb_queue_len(queue) <= 1) &&
            (sk->sk_protocol == IPPROTO_UDP) &&
            (rt->dst.dev->features & NETIF_F_UFO) && !dst_xfrm(&rt->dst) &&
-           (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, exthdrlen,
                                          transhdrlen, mtu, flags, fl6);