Messages in this thread | | | Date | Mon, 6 Jan 2014 21:21:30 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [PATCH] netfilter: nf_conntrack: release conntrack from rcu callback |
| |
On Mon, Jan 06, 2014 at 06:02:35PM +0100, Florian Westphal wrote: > > Can you elaborate? > Yes, nf_ct_is_dying(ct) might be called for the wrong conntrack. > > But, in case we _think_ that its the right one we call > nf_ct_tuple_equal() to verify we indeed found the right one: > > h = ____nf_conntrack_find(net, zone, tuple, hash); > if (h) { // might be released right now, but page won't go away (SLAB_BY_RCU) > ct = nf_ct_tuplehash_to_ctrack(h); > if (unlikely(nf_ct_is_dying(ct) || > !atomic_inc_not_zero(&ct->ct_general.use))) > // which means we should hit this path (0 ref). > h = NULL; > else { > // otherwise, it cannot go away from under us, since > // we own a reference now. > if (unlikely(!nf_ct_tuple_equal(tuple, &h->tuple) || > nf_ct_zone(ct) != zone)) { > // if we get here, the entry got recycled on other cpu > // for a different tuple, we can bail out and drop > // the reference safely and re-try the lookup > nf_ct_put(ct); > goto begin; > } > }
I think tuple may match if
task 1 task 2 task 3 nf_conntrack_find_get ____nf_conntrack_find destroy_conntrack hlist_nulls_del_rcu nf_conntrack_free kmem_cache_free __nf_conntrack_alloc kmem_cache_alloc if (nf_ct_is_dying(ct))
data is not yet cleaned
memset(&ct->tuplehash[IP_CT_DIR_MAX],
No? Or there something obvious I'm missing?
| |