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: [<ffffffff8149bd8c>] ip_setsockopt+0x7c/0xa0 #1: (&xt[i].mutex){+.+.+.}, at: [<ffffffff8148a5fe>] xt_find_table_lock+0x3e/0x110 stack backtrace: Pid: 3197, comm: iptables Not tainted 2.6.34-rc4 #2 Call Trace: [<ffffffff8105e2e8>] lockdep_rcu_dereference+0xb8/0xc0 [<ffffffff8147fb3b>] nf_ct_l3proto_module_put+0x6b/0x70 [<ffffffff8148d891>] state_mt_destroy+0x11/0x20 [<ffffffff814d3baf>] cleanup_match+0x2f/0x50 [<ffffffff814d3c63>] cleanup_entry+0x33/0x90 [<ffffffff814d5653>] ? __do_replace+0x1a3/0x210 [<ffffffff814d564c>] __do_replace+0x19c/0x210 [<ffffffff814d651a>] do_ipt_set_ctl+0x16a/0x1b0 [<ffffffff8147a610>] 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 <casteyde.christian@free.fr> Signed-off-by: Patrick McHardy <kaber@trash.net>
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@ -117,9 +117,13 @@ void nf_ct_l3proto_module_put(unsigned short l3proto)
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{
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{
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struct nf_conntrack_l3proto *p;
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struct nf_conntrack_l3proto *p;
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/* rcu_read_lock not necessary since the caller holds a reference */
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/* rcu_read_lock not necessary since the caller holds a reference, but
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* taken anyways to avoid lockdep warnings in __nf_ct_l3proto_find()
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*/
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rcu_read_lock();
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p = __nf_ct_l3proto_find(l3proto);
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p = __nf_ct_l3proto_find(l3proto);
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module_put(p->me);
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module_put(p->me);
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rcu_read_unlock();
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}
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}
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EXPORT_SYMBOL_GPL(nf_ct_l3proto_module_put);
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EXPORT_SYMBOL_GPL(nf_ct_l3proto_module_put);
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