Patch "ipv4: Should use consistent conditional judgement for ip fragment in __ip_append_data and ip_finish_output" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

ipv4: Should use consistent conditional judgement for ip fragment in __ip_append_data and ip_finish_output

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ipv4-should-use-consistent-conditional-judgement-for-ip-fragment-in-__ip_append_data-and-ip_finish_output.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: zheng li <[email protected]>
Date: Mon, 12 Dec 2016 09:56:05 +0800
Subject: ipv4: Should use consistent conditional judgement for ip fragment in __ip_append_data and ip_finish_output

From: zheng li <[email protected]>

[ Upstream commit 0a28cfd51e17f4f0a056bcf66bfbe492c3b99f38 ]

There is an inconsistent conditional judgement in __ip_append_data and ip_finish_output functions, the variable length in __ip_append_data just include the length of application's payload and udp header, don't include the length of ip header, but in ip_finish_output use (skb->len > ip_skb_dst_mtu(skb)) as judgement, and skb->len include the length of ip header.

That causes some particular application's udp payload whose length is between (MTU - IP Header) and MTU were fragmented by ip_fragment even though the rst->dev support UFO feature.

Add the length of ip header to length in __ip_append_data to keep consistent conditional judgement as ip_finish_output for ip fragment.

---
 net/ipv4/ip_output.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -936,7 +936,7 @@ static int __ip_append_data(struct sock
 		csummode = CHECKSUM_PARTIAL;
 
 	cork->length += length;
-	if (((length > mtu) || (skb && skb_is_gso(skb))) &&
+	if ((((length + fragheaderlen) > mtu) || (skb && skb_is_gso(skb))) &&
 	    (sk->sk_protocol == IPPROTO_UDP) &&
 	    (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len &&
 	    (sk->sk_type == SOCK_DGRAM) && !sk->sk_no_check_tx) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/ipv4-should-use-consistent-conditional-judgement-for-ip-fragment-in-__ip_append_data-and-ip_finish_output.patch