Patch "ipv6: tcp: add rcu locking in tcp_v6_send_synack()" has been added to the 4.4-stable tree

Patch "ipv6: tcp: add rcu locking in tcp_v6_send_synack()" has been added to the 4.4-stable tree

[gregkh]

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

    ipv6: tcp: add rcu locking in tcp_v6_send_synack()

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:
     ipv6-tcp-add-rcu-locking-in-tcp_v6_send_synack.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@vger.kernel.org> know about it.


>From foo@baz Tue Jan 26 21:31:27 PST 2016
From: Eric Dumazet <edumazet@google.com>
Date: Fri, 8 Jan 2016 09:35:51 -0800
Subject: ipv6: tcp: add rcu locking in tcp_v6_send_synack()

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 3e4006f0b86a5ae5eb0e8215f9a9e1db24506977 ]

When first SYNACK is sent, we already hold rcu_read_lock(), but this
is not true if a SYNACK is retransmitted, as a timer (soft) interrupt
does not hold rcu_read_lock()

Fixes: 45f6fad84cc30 ("ipv6: add complete rcu protection around np->opt")
Reported-by: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv6/tcp_ipv6.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -462,8 +462,10 @@ static int tcp_v6_send_synack(const stru
 		if (np->repflow && ireq->pktopts)
 			fl6->flowlabel = ip6_flowlabel(ipv6_hdr(ireq->pktopts));
 
+		rcu_read_lock();
 		err = ip6_xmit(sk, skb, fl6, rcu_dereference(np->opt),
 			       np->tclass);
+		rcu_read_unlock();
 		err = net_xmit_eval(err);
 	}
 


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

queue-4.4/ipv6-tcp-add-rcu-locking-in-tcp_v6_send_synack.patch
queue-4.4/ipv6-update-skb-csum-when-ce-mark-is-propagated.patch
queue-4.4/phonet-properly-unshare-skbs-in-phonet_rcv.patch
queue-4.4/tcp_yeah-don-t-set-ssthresh-below-2.patch