ipv4: Constrain UFO fragment sizes to multiples of 8 bytes

Because the ip fragment offset field counts 8-byte chunks, ip
fragments other than the last must contain a multiple of 8 bytes of
payload.  ip_ufo_append_data wasn't respecting this constraint and,
depending on the MTU and ip option sizes, could create malformed
non-final fragments.

Google-Bug-Id: 5009328
Signed-off-by: Bill Sommerfeld <wsommerfeld@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 3 deletions

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index be27e609a98b..ccaaa851ab42 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -734,7 +734,7 @@ static inline int ip_ufo_append_data(struct sock *sk,
                         int getfrag(void *from, char *to, int offset, int len,
                                int odd, struct sk_buff *skb),
                         void *from, int length, int hh_len, int fragheaderlen,
-                        int transhdrlen, int mtu, unsigned int flags)
+                        int transhdrlen, int maxfraglen, unsigned int flags)
 {
         struct sk_buff *skb;
         int err;
@@ -767,7 +767,7 @@ static inline int ip_ufo_append_data(struct sock *sk,
                 skb->csum = 0;
 
                 /* specify the length of each IP datagram fragment */
-                skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
+                skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen;
                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
                 __skb_queue_tail(queue, skb);
         }
@@ -831,7 +831,7 @@ static int __ip_append_data(struct sock *sk,
             (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len) {
                 err = ip_ufo_append_data(sk, queue, getfrag, from, length,
                                          hh_len, fragheaderlen, transhdrlen,
-                                         mtu, flags);
+                                         maxfraglen, flags);
                 if (err)
                         goto error;
                 return 0;