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 4.4-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-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Wed Aug 9 11:19:16 PDT 2017 From: zheng li <james.z.li@xxxxxxxxxxxx> 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 <james.z.li@xxxxxxxxxxxx> [ 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. Signed-off-by: Zheng Li <james.z.li@xxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/ipv4/ip_output.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -922,7 +922,7 @@ 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 james.z.li@xxxxxxxxxxxx are queue-4.4/ipv4-should-use-consistent-conditional-judgement-for-ip-fragment-in-__ip_append_data-and-ip_finish_output.patch