Patch "tcp: initialize tp->copied_seq in case of cross SYN connection" has been added to the 4.3-stable tree

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

    tcp: initialize tp->copied_seq in case of cross SYN connection

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-initialize-tp-copied_seq-in-case-of-cross-syn-connection.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 <[email protected]> know about it.

From: Eric Dumazet <[email protected]>
Date: Thu, 26 Nov 2015 08:18:14 -0800
Subject: tcp: initialize tp->copied_seq in case of cross SYN connection

From: Eric Dumazet <[email protected]>

[ Upstream commit 142a2e7ece8d8ac0e818eb2c91f99ca894730e2a ]

Dmitry provided a syzkaller (http://github.com/google/syzkaller)
generated program that triggers the WARNING at net/ipv4/tcp.c:1729 in tcp_recvmsg() :

WARN_ON(tp->copied_seq != tp->rcv_nxt &&

        !(flags & (MSG_PEEK | MSG_TRUNC)));

His program is specifically attempting a Cross SYN TCP exchange, that we support (for the pleasure of hackers ?), but it looks we lack proper tcp->copied_seq initialization.

Thanks again Dmitry for your report and testings.

---
 net/ipv4/tcp_input.c |    1 +
 1 file changed, 1 insertion(+)

@@ -5659,6 +5659,7 @@ discard:
 		}
 
 		tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
+		tp->copied_seq = tp->rcv_nxt;
 		tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
 
 		/* RFC1323: The window in SYN & SYN/ACK segments is

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

queue-4.3/ipv6-add-complete-rcu-protection-around-np-opt.patch queue-4.3/packet-infer-protocol-from-ethernet-header-if-unset.patch queue-4.3/af-unix-passcred-support-for-sendpage.patch queue-4.3/ipv6-sctp-implement-sctp_v6_destroy_sock.patch queue-4.3/af_unix-don-t-append-consumed-skbs-to-sk_receive_queue.patch queue-4.3/tcp-disable-fast-open-on-timeouts-after-handshake.patch queue-4.3/net-scm-fix-pax-detected-msg_controllen-overflow-in-scm_detach_fds.patch queue-4.3/tcp-md5-fix-lockdep-annotation.patch queue-4.3/af-unix-fix-use-after-free-with-concurrent-readers-while-splicing.patch queue-4.3/net_sched-fix-qdisc_tree_decrease_qlen-races.patch queue-4.3/tcp-initialize-tp-copied_seq-in-case-of-cross-syn-connection.patch queue-4.3/tcp-fix-potential-huge-kmalloc-calls-in-tcp_repair.patch queue-4.3/packet-do-skb_probe_transport_header-when-we-actually-have-data.patch queue-4.3/af_unix-take-receive-queue-lock-while-appending-new-skb.patch queue-4.3/r8169-fix-kasan-reported-skb-use-after-free.patch