From 3b254c54ec46eb022cb26ee6ab37fae23f5f7d6a Mon Sep 17 00:00:00 2001 From: Patrick McHardy Date: Mon, 10 May 2010 17:45:56 +0200 Subject: [PATCH] netfilter: nf_conntrack_proto: fix warning with CONFIG_PROVE_RCU =================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- include/net/netfilter/nf_conntrack_l3proto.h:92 invoked rcu_dereference_check() without protection! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 0 2 locks held by iptables/3197: #0: (sk_lock-AF_INET){+.+.+.}, at: [] ip_setsockopt+0x7c/0xa0 #1: (&xt[i].mutex){+.+.+.}, at: [] xt_find_table_lock+0x3e/0x110 stack backtrace: Pid: 3197, comm: iptables Not tainted 2.6.34-rc4 #2 Call Trace: [] lockdep_rcu_dereference+0xb8/0xc0 [] nf_ct_l3proto_module_put+0x6b/0x70 [] state_mt_destroy+0x11/0x20 [] cleanup_match+0x2f/0x50 [] cleanup_entry+0x33/0x90 [] ? __do_replace+0x1a3/0x210 [] __do_replace+0x19c/0x210 [] do_ipt_set_ctl+0x16a/0x1b0 [] nf_sockopt+0x60/0xa0 ... The __nf_ct_l3proto_find() call doesn't actually need rcu read side protection since the caller holds a reference to the protocol. Use rcu_read_lock() anyways to avoid the warning. Kernel bugzilla #15781: https://bugzilla.kernel.org/show_bug.cgi?id=15781 Reported-by: Christian Casteyde Signed-off-by: Patrick McHardy --- net/netfilter/nf_conntrack_proto.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/net/netfilter/nf_conntrack_proto.c b/net/netfilter/nf_conntrack_proto.c index a6defc793601..5886ba1d52a0 100644 --- a/net/netfilter/nf_conntrack_proto.c +++ b/net/netfilter/nf_conntrack_proto.c @@ -117,9 +117,13 @@ void nf_ct_l3proto_module_put(unsigned short l3proto) { struct nf_conntrack_l3proto *p; - /* rcu_read_lock not necessary since the caller holds a reference */ + /* rcu_read_lock not necessary since the caller holds a reference, but + * taken anyways to avoid lockdep warnings in __nf_ct_l3proto_find() + */ + rcu_read_lock(); p = __nf_ct_l3proto_find(l3proto); module_put(p->me); + rcu_read_unlock(); } EXPORT_SYMBOL_GPL(nf_ct_l3proto_module_put); -- 2.34.1