Andrey Vagin <avagin@xxxxxxxxxx> wrote: > ---- > Eric and Florian, could you look at this patch. When you say, > that it looks good, I will ask the user to validate it. > I can't reorder these actions, because it's reproduced on a real host > with real users. Thanks. > ---- > > nf_conntrack_free can't be called for a conntract with non-zero ref-counter, > because it can race with nf_conntrack_find_get(). Indeed. > A conntrack slab is created with SLAB_DESTROY_BY_RCU. Non-zero > ref-conunter says that this conntrack is used now. So when we release a > conntrack with non-zero counter, we break this assumption. > > CPU1 CPU2 > ____nf_conntrack_find() > nf_ct_put() > destroy_conntrack() > ... > init_conntrack > __nf_conntrack_alloc (set use = 1) > atomic_inc_not_zero(&ct->use) (use = 2) > if (!l4proto->new(ct, skb, dataoff, timeouts)) > nf_conntrack_free(ct); (use = 2 !!!) > ... Yes, I think this sequence is possible; we must not use nf_conntrack_free here. > - /* We overload first tuple to link into unconfirmed or dying list.*/ > - BUG_ON(hlist_nulls_unhashed(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode)); > - hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode); > + if (!hlist_nulls_unhashed(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode)) > + hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode); This is the only thing that I don't like about this patch. Currently all the conntracks in the system are always put on a list before they're supposed to be visible/handled via refcnt system (unconfirmed, hash, or dying list). I think it would be nice if we could keep it that way. If everything fails we could proably intoduce a 'larval' dummy list similar to the one used by template conntracks? -- To unsubscribe from this list: send the line "unsubscribe netfilter" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
