udp: consistently apply ufo or fragmentation

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commit 85f1bd9a7b upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.16:
 - ip6_append_data() doesn't take a queue parameter; use &sk->sk_write_queue
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

...

This commit is contained in:

Willem de Bruijn 2017-08-10 12:29:19 -04:00 • committed by Ben Hutchings

parent df3d6afcee

commit 08676246d8

3 changed files with 10 additions and 6 deletions

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7

net/ipv4/ip_output.c

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2

net/ipv4/udp.c

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7

net/ipv6/ip6_output.c

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