This is a note to let you know that I've just added the patch titled
netfilter: conntrack: fix possible bug_on with enable_hooks=1
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
netfilter-conntrack-fix-possible-bug_on-with-enable_.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 9a709cec07d708e4be03adde35397e42f75e0980
Author: Florian Westphal <fw@xxxxxxxxx>
Date: Thu May 4 14:55:02 2023 +0200
netfilter: conntrack: fix possible bug_on with enable_hooks=1
[ 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>
diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index 6e80f0f6149ea..55a7f72d547cd 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -699,9 +699,11 @@ 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 460294bd4b606..52245dbfae311 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -1222,11 +1222,12 @@ 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:
