From 54ab49fde95605a1077f759ce454d94e84b5ca45 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Sun, 10 May 2020 14:28:07 +0200 Subject: [PATCH] netfilter: conntrack: fix infinite loop on rmmod 'rmmod nf_conntrack' can hang forever, because the netns exit gets stuck in nf_conntrack_cleanup_net_list(): i_see_dead_people: busy = 0; list_for_each_entry(net, net_exit_list, exit_list) { nf_ct_iterate_cleanup(kill_all, net, 0, 0); if (atomic_read(&net->ct.count) != 0) busy = 1; } if (busy) { schedule(); goto i_see_dead_people; } When nf_ct_iterate_cleanup iterates the conntrack table, all nf_conn structures can be found twice: once for the original tuple and once for the conntracks reply tuple. get_next_corpse() only calls the iterator when the entry is in original direction -- the idea was to avoid unneeded invocations of the iterator callback. When support for clashing entries was added, the assumption that all nf_conn objects are added twice, once in original, once for reply tuple no longer holds -- NF_CLASH_BIT entries are only added in the non-clashing reply direction. Thus, if at least one NF_CLASH entry is in the list then nf_conntrack_cleanup_net_list() always skips it completely. During normal netns destruction, this causes a hang of several seconds, until the gc worker removes the entry (NF_CLASH entries always have a 1 second timeout). But in the rmmod case, the gc worker has already been stopped, so ct.count never becomes 0. We can fix this in two ways: 1. Add a second test for CLASH_BIT and call iterator for those entries as well, or: 2. Skip the original tuple direction and use the reply tuple. 2) is simpler, so do that. Fixes: 6a757c07e51f80ac ("netfilter: conntrack: allow insertion of clashing entries") Reported-by: Chen Yi Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_conntrack_core.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index 0173398f4ced..1d57b95d3481 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -2139,8 +2139,19 @@ get_next_corpse(int (*iter)(struct nf_conn *i, void *data), nf_conntrack_lock(lockp); if (*bucket < nf_conntrack_htable_size) { hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[*bucket], hnnode) { - if (NF_CT_DIRECTION(h) != IP_CT_DIR_ORIGINAL) + if (NF_CT_DIRECTION(h) != IP_CT_DIR_REPLY) continue; + /* All nf_conn objects are added to hash table twice, one + * for original direction tuple, once for the reply tuple. + * + * Exception: In the IPS_NAT_CLASH case, only the reply + * tuple is added (the original tuple already existed for + * a different object). + * + * We only need to call the iterator once for each + * conntrack, so we just use the 'reply' direction + * tuple while iterating. + */ ct = nf_ct_tuplehash_to_ctrack(h); if (iter(ct, data)) goto found; -- 2.20.1