Patch "ipv6: fix a lockdep splat" has been added to the 4.4-stable tree

Patch "ipv6: fix a lockdep splat" 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: fix a lockdep splat

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-fix-a-lockdep-splat.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 Mon Feb 29 14:33:50 PST 2016
From: Eric Dumazet <edumazet@google.com>
Date: Tue, 2 Feb 2016 17:55:01 -0800
Subject: ipv6: fix a lockdep splat

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 44c3d0c1c0a880354e9de5d94175742e2c7c9683 ]

Silence lockdep false positive about rcu_dereference() being
used in the wrong context.

First one should use rcu_dereference_protected() as we own the spinlock.

Second one should be a normal assignation, as no barrier is needed.

Fixes: 18367681a10bd ("ipv6 flowlabel: Convert np->ipv6_fl_list to RCU.")
Reported-by: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv6/ip6_flowlabel.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/net/ipv6/ip6_flowlabel.c
+++ b/net/ipv6/ip6_flowlabel.c
@@ -540,12 +540,13 @@ int ipv6_flowlabel_opt(struct sock *sk,
 		}
 		spin_lock_bh(&ip6_sk_fl_lock);
 		for (sflp = &np->ipv6_fl_list;
-		     (sfl = rcu_dereference(*sflp)) != NULL;
+		     (sfl = rcu_dereference_protected(*sflp,
+						      lockdep_is_held(&ip6_sk_fl_lock))) != NULL;
 		     sflp = &sfl->next) {
 			if (sfl->fl->label == freq.flr_label) {
 				if (freq.flr_label == (np->flow_label&IPV6_FLOWLABEL_MASK))
 					np->flow_label &= ~IPV6_FLOWLABEL_MASK;
-				*sflp = rcu_dereference(sfl->next);
+				*sflp = sfl->next;
 				spin_unlock_bh(&ip6_sk_fl_lock);
 				fl_release(sfl->fl);
 				kfree_rcu(sfl, rcu);


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

queue-4.4/ipv4-fix-memory-leaks-in-ip_cmsg_send-callers.patch
queue-4.4/tcp-dccp-fix-another-race-at-listener-dismantle.patch
queue-4.4/ipv6-fix-a-lockdep-splat.patch
queue-4.4/ipv6-addrconf-fix-recursive-spin-lock-call.patch
queue-4.4/tcp-do-not-drop-syn_recv-on-all-icmp-reports.patch
queue-4.4/tcp-beware-of-alignments-in-tcp_get_info.patch
queue-4.4/tcp-md5-release-request-socket-instead-of-listener.patch
queue-4.4/gro-make-gro-aware-of-lightweight-tunnels.patch
queue-4.4/tcp-fix-null-deref-in-tcp_v4_send_ack.patch
queue-4.4/af_unix-fix-struct-pid-memory-leak.patch
queue-4.4/net-add-sysctl_max_skb_frags.patch