From: Patrick McHardy <kaber@xxxxxxxxx>
===================================================
[ 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@xxxxxxx>
Signed-off-by: Patrick McHardy <kaber@xxxxxxxxx>
---
net/netfilter/nf_conntrack_proto.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/net/netfilter/nf_conntrack_proto.c b/net/netfilter/nf_conntrack_proto.c
index a6defc7..5886ba1 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);
--
1.7.0.4
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