From: Florian Westphal fw@strlen.de
[ 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@strlen.de Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 60332fdb6dd44..5b7578adbf0f1 100644 --- a/net/netfilter/core.c +++ b/net/netfilter/core.c @@ -674,9 +674,11 @@ 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 e12b52019a550..b613de96ad855 100644 --- a/net/netfilter/nf_conntrack_standalone.c +++ b/net/netfilter/nf_conntrack_standalone.c @@ -1170,11 +1170,12 @@ 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: