@@ -1073,12 +1073,12 @@
static void __exit nf_log_syslog_exit(void)
{
- unregister_pernet_subsys(&nf_log_syslog_net_ops);
nf_log_unregister(&nf_ip_logger);
nf_log_unregister(&nf_arp_logger);
nf_log_unregister(&nf_ip6_logger);
nf_log_unregister(&nf_netdev_logger);
nf_log_unregister(&nf_bridge_logger);
+ unregister_pernet_subsys(&nf_log_syslog_net_ops);
}
module_init(nf_log_syslog_init);
@@ -1233,8 +1233,8 @@
{
nfnetlink_subsys_unregister(&nfulnl_subsys);
netlink_unregister_notifier(&nfulnl_rtnl_notifier);
- unregister_pernet_subsys(&nfnl_log_net_ops);
nf_log_unregister(&nfulnl_logger);
+ unregister_pernet_subsys(&nfnl_log_net_ops);
}
MODULE_DESCRIPTION("netfilter userspace logging");
nf_log_syslog and nfnetlink_log unregister their per-network namespace operations before unregistering their global logger backends. This leaves a window where a sysctl or netlink writer can rebind the still- registered logger after the per-net pre-exit callback cleared the old selection. The race looks like this: CPU 0 CPU 1 ---- ---- unregister_pernet_subsys() nf_log_unset(net, logger) net->nf.nf_loggers[pf] = NULL lock nf_log_mutex find logger in loggers[][] net->nf.nf_loggers[pf] = logger unlock nf_log_mutex nf_log_unregister(logger) lock nf_log_mutex loggers[pf][type] = NULL unlock nf_log_mutex synchronize_rcu() module exit returns module core frees backend memory Later, a sysctl read or packet logging operation can dereference the stale per-net logger pointer. Fix this by unregistering the global logger backends before tearing down per-net state. Once the global registrations are gone, later writers can no longer rebind the logger. unregister_pernet_subsys() already waits for an RCU grace period after the pre-exit callback clears the per-net selection, while nf_log_unregister() continues to cover readers of the global logger table. Apply this ordering fix to both nf_log backends that combine per-net teardown with global logger registration. Fixes: 5b023fc8d8e0 ("netfilter: enable per netns support for nf_loggers") Cc: stable@vger.kernel.org Signed-off-by: Chengfeng Ye <nicoyip.dev@gmail.com> --- Changes in v2: - Rework the fix around backend teardown ordering instead of clearing per-net bindings from nf_log_unregister(). - Apply the ordering fix to both nf_log_syslog and nfnetlink_log. - Drop the redundant trailing synchronize_rcu(). Link: https://lore.kernel.org/netdev/20260822184658.3787672-1-nicoyip.dev@gmail.com/ [v1] --- net/netfilter/nf_log_syslog.c | 2 +- net/netfilter/nfnetlink_log.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)