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

    tcp: restore fastopen with no data in SYN packet

to the 4.3-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:
     tcp-restore-fastopen-with-no-data-in-syn-packet.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Wed Dec 30 19:48:47 PST 2015
From: Eric Dumazet <eduma...@google.com>
Date: Wed, 16 Dec 2015 13:53:10 -0800
Subject: tcp: restore fastopen with no data in SYN packet

From: Eric Dumazet <eduma...@google.com>

[ Upstream commit 07e100f984975cb0417a7d5e626d0409efbad478 ]

Yuchung tracked a regression caused by commit 57be5bdad759 ("ip: convert
tcp_sendmsg() to iov_iter primitives") for TCP Fast Open.

Some Fast Open users do not actually add any data in the SYN packet.

Fixes: 57be5bdad759 ("ip: convert tcp_sendmsg() to iov_iter primitives")
Reported-by: Yuchung Cheng <ych...@google.com>
Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: Al Viro <v...@zeniv.linux.org.uk>
Acked-by: Yuchung Cheng <ych...@google.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/ipv4/tcp_output.c |   23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3147,7 +3147,7 @@ static int tcp_send_syn_data(struct sock
 {
        struct tcp_sock *tp = tcp_sk(sk);
        struct tcp_fastopen_request *fo = tp->fastopen_req;
-       int syn_loss = 0, space, err = 0, copied;
+       int syn_loss = 0, space, err = 0;
        unsigned long last_syn_loss = 0;
        struct sk_buff *syn_data;
 
@@ -3185,17 +3185,18 @@ static int tcp_send_syn_data(struct sock
                goto fallback;
        syn_data->ip_summed = CHECKSUM_PARTIAL;
        memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
-       copied = copy_from_iter(skb_put(syn_data, space), space,
-                               &fo->data->msg_iter);
-       if (unlikely(!copied)) {
-               kfree_skb(syn_data);
-               goto fallback;
-       }
-       if (copied != space) {
-               skb_trim(syn_data, copied);
-               space = copied;
+       if (space) {
+               int copied = copy_from_iter(skb_put(syn_data, space), space,
+                                           &fo->data->msg_iter);
+               if (unlikely(!copied)) {
+                       kfree_skb(syn_data);
+                       goto fallback;
+               }
+               if (copied != space) {
+                       skb_trim(syn_data, copied);
+                       space = copied;
+               }
        }
-
        /* No more data pending in inet_wait_for_connect() */
        if (space == fo->size)
                fo->data = NULL;


Patches currently in stable-queue which might be from eduma...@google.com are

queue-4.3/inet-tcp-fix-inetpeer_set_addr_v4.patch
queue-4.3/ipv6-sctp-clone-options-to-avoid-use-after-free.patch
queue-4.3/tcp-restore-fastopen-with-no-data-in-syn-packet.patch
queue-4.3/net_sched-make-qdisc_tree_decrease_qlen-work-for-non-mq.patch
queue-4.3/net-fix-ip-early-demux-races.patch
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