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Groups > linux.kernel > #1350112

[PATCH 3.12 011/116] ipv6: fix a lockdep splat

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From: Eric Dumazet <edumazet@google.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

[ 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: Jiri Slaby <jslaby@suse.cz>
---
 net/ipv6/ip6_flowlabel.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/ip6_flowlabel.c b/net/ipv6/ip6_flowlabel.c
index f0ccdb787100..d14c74b2dfa3 100644
--- a/net/ipv6/ip6_flowlabel.c
+++ b/net/ipv6/ip6_flowlabel.c
@@ -527,12 +527,13 @@ int ipv6_flowlabel_opt(struct sock *sk, char __user *optval, int optlen)
 	case IPV6_FL_A_PUT:
 		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);
-- 
2.7.2

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[PATCH 3.12 000/116] 3.12.56-stable review Jiri Slaby <jslaby@suse.cz> - 2016-03-04 10:10 +0100
  [PATCH 3.12 001/116] proc: Fix ptrace-based permission checks for accessing task maps Jiri Slaby <jslaby@suse.cz> - 2016-03-04 11:00 +0100
    [PATCH 3.12 016/116] bonding: Fix ARP monitor validation Jiri Slaby <jslaby@suse.cz> - 2016-03-04 11:00 +0100
    [PATCH 3.12 007/116] pptp: fix illegal memory access caused by multiple bind()s Jiri Slaby <jslaby@suse.cz> - 2016-03-04 11:00 +0100
    [PATCH 3.12 012/116] net:Add sysctl_max_skb_frags Jiri Slaby <jslaby@suse.cz> - 2016-03-04 11:00 +0100
    [PATCH 3.12 006/116] af_unix: fix struct pid memory leak Jiri Slaby <jslaby@suse.cz> - 2016-03-04 11:00 +0100
    [PATCH 3.12 008/116] sctp: allow setting SCTP_SACK_IMMEDIATELY by the application Jiri Slaby <jslaby@suse.cz> - 2016-03-04 11:00 +0100
    [PATCH 3.12 009/116] ipv6/udp: use sticky pktinfo egress ifindex on connect() Jiri Slaby <jslaby@suse.cz> - 2016-03-04 11:00 +0100
    [PATCH 3.12 011/116] ipv6: fix a lockdep splat Jiri Slaby <jslaby@suse.cz> - 2016-03-04 11:00 +0100
    [PATCH 3.12 015/116] bonding: fix bond_arp_rcv() race of curr_active_slave Jiri Slaby <jslaby@suse.cz> - 2016-03-04 11:00 +0100
  Re: [PATCH 3.12 000/116] 3.12.56-stable review Guenter Roeck <linux@roeck-us.net> - 2016-03-04 15:10 +0100
    Re: [PATCH 3.12 000/116] 3.12.56-stable review Jiri Slaby <jslaby@suse.cz> - 2016-03-08 16:50 +0100
  Re: [PATCH 3.12 000/116] 3.12.56-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2016-03-04 15:50 +0100

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