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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: e89e9cf539 ("[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>
This commit is contained in:
Willem de Bruijn 2017-08-10 12:29:19 -04:00 committed by David S. Miller
parent 96d9703050
commit 85f1bd9a7b
3 changed files with 10 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
net/ipv4/ip_output.c
View File

@ -965,11 +965,12 @@ 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);
@ -1288,6 +1289,7 @@ 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)

2
net/ipv4/udp.c
View File

@ -802,7 +802,7 @@ 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;

7
net/ipv6/ip6_output.c
View File

@ -1381,11 +1381,12 @@ 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);