From: Liping Zhang zlpnobody@gmail.com
[ Upstream commit fefa92679dbe0c613e62b6c27235dcfbe9640ad1 ]
If nf_conntrack_htable_size was adjusted by the user during the ct dump operation, we may invoke nf_ct_put twice for the same ct, i.e. the "last" ct. This will cause the ct will be freed but still linked in hash buckets.
It's very easy to reproduce the problem by the following commands: # while : ; do echo $RANDOM > /proc/sys/net/netfilter/nf_conntrack_buckets done # while : ; do conntrack -L done # iperf -s 127.0.0.1 & # iperf -c 127.0.0.1 -P 60 -t 36000
After a while, the system will hang like this: NMI watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [bash:20184] NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [iperf:20382] ...
So at last if we find cb->args[1] is equal to "last", this means hash resize happened, then we can set cb->args[1] to 0 to fix the above issue.
Fixes: d205dc40798d ("[NETFILTER]: ctnetlink: fix deadlock in table dumping") Signed-off-by: Liping Zhang zlpnobody@gmail.com Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- net/netfilter/nf_conntrack_netlink.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c index 660939df7c94..3a6f0fa08338 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -887,8 +887,13 @@ ctnetlink_dump_table(struct sk_buff *skb, struct netlink_callback *cb) } out: local_bh_enable(); - if (last) + if (last) { + /* nf ct hash resize happened, now clear the leftover. */ + if ((struct nf_conn *)cb->args[1] == last) + cb->args[1] = 0; + nf_ct_put(last); + }
return skb->len; }