From a8c4a2522a0808c5c2143612909717d1115c40cf Mon Sep 17 00:00:00 2001 From: Hannes Frederic Sowa Date: Mon, 22 Feb 2016 18:43:25 +0100 Subject: 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 d749c9cbffd6 ("ipv4: no CHECKSUM_PARTIAL on MSG_MORE corked sockets") started to exposes this bug. Fixes: d749c9cbffd6 ("ipv4: no CHECKSUM_PARTIAL on MSG_MORE corked sockets") Reported-by: Jiri Benc Cc: Jiri Benc Reported-by: Wakko Warner Cc: Wakko Warner Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index 64878ef..565bf64 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -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)) { -- cgit v0.10.2