Hi Florian,
On Fri, Feb 10, 2023 at 11:32:50AM +0100, Florian Westphal wrote:
> Hangyu Hua <hbh25y@xxxxxxxxx> wrote:
> > nf_ct_put() needs to be called to put the refcount got by
> > nf_conntrack_find_get() to avoid refcount leak when
> > nf_conntrack_hash_check_insert() fails.
> >
> > Fixes: 7d367e06688d ("netfilter: ctnetlink: fix soft lockup when netlink adds new entries (v2)")
> > Signed-off-by: Hangyu Hua <hbh25y@xxxxxxxxx>
> > ---
> > net/netfilter/nf_conntrack_netlink.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
> > index 1286ae7d4609..ca4d5bb1ea52 100644
> > --- a/net/netfilter/nf_conntrack_netlink.c
> > +++ b/net/netfilter/nf_conntrack_netlink.c
> > @@ -2375,12 +2375,15 @@ ctnetlink_create_conntrack(struct net *net,
> >
> > err = nf_conntrack_hash_check_insert(ct);
> > if (err < 0)
> > - goto err2;
> > + goto err3;
>
> Ouch, looks like this is broken in more than one way?
>
> nf_conntrack_hash_check_insert() can call nf_ct_kill()
> and return an error, in that case ct->master reference
> is already dropped for us.
>
> One way would be to return 0 in that case (in
> nf_conntrack_hash_check_insert()). What do you think?
This is misleading to the user that adds an entry via ctnetlink?
ETIMEDOUT also looks a bit confusing to report to userspace.
Rewinding: if the intention is to deal with stale conntrack extension,
for example, helper module has been removed while this entry was
added. Then, probably call EAGAIN so nfnetlink has a chance to retry
transparently?
BTW, I think we should remove:
NF_CT_STAT_INC_ATOMIC(net, drop);
that is under nf_ct_ext_valid_post(), no packet is dropped in this
path.
Thanks.
