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Commit a8c4a252 authored by Hannes Frederic Sowa's avatar Hannes Frederic Sowa Committed by David S. Miller
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ipv4: only create late gso-skb if skb is already set up with CHECKSUM_PARTIAL 



Otherwise we break the contract with GSO to only pass CHECKSUM_PARTIAL
skbs down. This can easily happen with UDP+IPv4 sockets with the first
MSG_MORE write smaller than the MTU, second write is a sendfile.

Returning -EOPNOTSUPP lets the callers fall back into normal sendmsg path,
were we calculate the checksum manually during copying.

Commit d749c9cb ("ipv4: no CHECKSUM_PARTIAL on MSG_MORE corked
sockets") started to exposes this bug.

Fixes: d749c9cb ("ipv4: no CHECKSUM_PARTIAL on MSG_MORE corked sockets")
Reported-by: default avatarJiri Benc <jbenc@redhat.com>
Cc: Jiri Benc <jbenc@redhat.com>
Reported-by: default avatarWakko Warner <wakko@animx.eu.org>
Cc: Wakko Warner <wakko@animx.eu.org>
Signed-off-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c7dfe3ab

net/ipv4/ip_output.c

+4 −1
Original line number Diff line number Diff line
@@ -1236,13 +1236,16 @@ ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page, 
	if (!skb)

		return -EINVAL;



	cork->length += size;

	if ((size + skb->len > mtu) &&

	    (sk->sk_protocol == IPPROTO_UDP) &&

	    (rt->dst.dev->features & NETIF_F_UFO)) {

		if (skb->ip_summed != CHECKSUM_PARTIAL)

			return -EOPNOTSUPP;



		skb_shinfo(skb)->gso_size = mtu - fragheaderlen;

		skb_shinfo(skb)->gso_type = SKB_GSO_UDP;

	}

	cork->length += size;



	while (size > 0) {

		if (skb_is_gso(skb)) {