On Thu, Jan 03, 2019 at 12:28:46AM +0000, Alakesh Haloi wrote:
> commit b36e4523d4d5 ("netfilter: nf_conncount: fix garbage collection confirm
> race")
>
> An iptable rule like the following on a multicore systems will result in
> accepting more connections than set in the rule.
>
> iptables -A INPUT -p tcp -m tcp --syn --dport 7777 -m connlimit \
> --connlimit-above 2000 --connlimit-mask 0 -j DROP
>
> In check_hlist function, connections that are found in saved connections
> but not in netfilter conntrack are deleted, assuming that those
> connections do not exist anymore. But for multi core systems, there exists
> a small time window, when a connection has been added to the xt_connlimit
> maintained rb-tree but has not yet made to netfilter conntrack table. This
> causes concurrent connections to return incorrect counts and go over limit
> set in iptable rule.
>
> The fix has been partially backported from the above mentioned upstream
> commit. Introduce timestamp and the owning cpu.
>
> Signed-off-by: Alakesh Haloi <alakeshh@xxxxxxxxxx>
> Cc: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
> Cc: Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxxxxxx>
> Cc: Florian Westphal <fw@xxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # v4.15 and before
But 4.14.92 already b36e4523d4d5 ("netfilter: nf_conncount: fix garbage
collection confirm race") and 4cd273bb91b3 ("netfilter: nf_conncount:
don't skip eviction when age is negative") in it. Are you sure you
still need this patch?
thanks,
greg k-h
