From: Florian Westphal <fw@xxxxxxxxx>
[ Upstream commit e72eeab542dbf4f544e389e64fa13b82a1b6d003 ]
I received a bug report (no reproducer so far) where we trip over
712 rcu_read_lock();
713 ct_hook = rcu_dereference(nf_ct_hook);
714 BUG_ON(ct_hook == NULL); // here
In nf_conntrack_destroy().
First turn this BUG_ON into a WARN. I think it was triggered
via enable_hooks=1 flag.
When this flag is turned on, the conntrack hooks are registered
before nf_ct_hook pointer gets assigned.
This opens a short window where packets enter the conntrack machinery,
can have skb->_nfct set up and a subsequent kfree_skb might occur
before nf_ct_hook is set.
Call nf_conntrack_init_end() to set nf_ct_hook before we register the
pernet ops.
Fixes: ba3fbe663635 ("netfilter: nf_conntrack: provide modparam to always register conntrack hooks")
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/netfilter/core.c | 6 ++++--
net/netfilter/nf_conntrack_standalone.c | 3 ++-
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index cca0762a90102..8eed6536e7e7b 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -675,9 +675,11 @@ void nf_conntrack_destroy(struct nf_conntrack *nfct)
rcu_read_lock();
ct_hook = rcu_dereference(nf_ct_hook);
- BUG_ON(ct_hook == NULL);
- ct_hook->destroy(nfct);
+ if (ct_hook)
+ ct_hook->destroy(nfct);
rcu_read_unlock();
+
+ WARN_ON(!ct_hook);
}
EXPORT_SYMBOL(nf_conntrack_destroy);
diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 338f02a12076b..7515705583bcf 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -1229,11 +1229,12 @@ static int __init nf_conntrack_standalone_init(void)
nf_conntrack_htable_size_user = nf_conntrack_htable_size;
#endif
+ nf_conntrack_init_end();
+
ret = register_pernet_subsys(&nf_conntrack_net_ops);
if (ret < 0)
goto out_pernet;
- nf_conntrack_init_end();
return 0;
out_pernet:
--
2.39.2
