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    SubjectRe: [PATCH] ebtables: fix race condition in frame_filter_net_init()
    On Tue, Sep 26, 2017 at 02:42:11PM +0200, Florian Westphal wrote:
    > Artem Savkov <asavkov@redhat.com> wrote:
    > > It is possible for ebt_in_hook to be triggered before ebt_table is assigned
    > > resulting in a NULL-pointer dereference. Make sure hooks are
    > > registered as the last step.
    >
    > Right, thanks for the patch.
    >
    > > --- a/net/bridge/netfilter/ebtable_broute.c
    > > +++ b/net/bridge/netfilter/ebtable_broute.c
    > > @@ -65,7 +65,7 @@ static int ebt_broute(struct sk_buff *skb)
    > >
    > > static int __net_init broute_net_init(struct net *net)
    > > {
    > > - net->xt.broute_table = ebt_register_table(net, &broute_table, NULL);
    > > + net->xt.broute_table = ebt_register_table(net, &broute_table);
    >
    > I wonder if it makes more sense to model this like the iptables version,
    > i.e. pass net->xt.table_name as last arg to ebt_register_table ...
    >
    > > +int ebt_register_hooks(struct net *net, struct ebt_table *table,
    > > + const struct nf_hook_ops *ops)
    > > +{
    > > + int ret = nf_register_net_hooks(net, ops, hweight32(table->valid_hooks));
    > > +
    > > + if (ret)
    > > + __ebt_unregister_table(net, table);
    > > +
    > > + return ret;
    > > +}
    >
    > ... because this looks strange (unregister of table/not-so-obvious error
    > unwinding ...)
    >
    > > @@ -1252,15 +1262,6 @@ ebt_register_table(struct net *net, const struct ebt_table *input_table,
    > > list_add(&table->list, &net->xt.tables[NFPROTO_BRIDGE]);
    > > mutex_unlock(&ebt_mutex);
    >
    > ... here one could then assign the net->xt.table_X pointer, and then do
    > the hook registration right after.
    >
    > However i have no strong opinion here.

    Agreed, that does look better and requires less changes. I'll send a v2.

    --
    Regards,
    Artem

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