Quoting Samu Kallio:
Basically what's happening is, during netns cleanup,
nf_nat_net_exit gets called before ipv4_net_exit. As I understand
it, nf_nat_net_exit is supposed to kill any conntrack entries which
have NAT context (through nf_ct_iterate_cleanup), but for some
reason this doesn't happen (perhaps something else is still holding
refs to those entries?).
When ipv4_net_exit is called, conntrack entries (including those
with NAT context) are cleaned up, but the
nat_bysource hashtable is long gone - freed in nf_nat_net_exit. The
bug happens when attempting to free a conntrack entry whose NAT hash
'prev' field points to a slot in the freed hash table (head for that
bin).
We ignore conntracks with null nat bindings. But this is wrong,
as these are in bysource hash table as well.
Restore nat-cleaning for the netns-is-being-removed case.
bug:
https://bugzilla.kernel.org/show_bug.cgi?id=65191
Fixes: c2d421e171 ('netfilter: nf_nat: fix race when unloading protocol modules')
Reported-by: Samu Kallio <samu.kallio@aberdeencloud.com>
Debugged-by: Samu Kallio <samu.kallio@aberdeencloud.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Tested-by: Samu Kallio <samu.kallio@aberdeencloud.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
