From e759e1e4a4bd2926d082afe56046a90224433a31 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 29 Jan 2025 14:27:26 +0000 Subject: [PATCH] net: revert RTNL changes in unregister_netdevice_many_notify() This patch reverts following changes: 83419b61d187 net: reduce RTNL hold duration in unregister_netdevice_many_notify() (part 2) ae646f1a0bb9 net: reduce RTNL hold duration in unregister_netdevice_many_notify() (part 1) cfa579f66656 net: no longer hold RTNL while calling flush_all_backlogs() This caused issues in layers holding a private mutex: cleanup_net() rtnl_lock(); mutex_lock(subsystem_mutex); unregister_netdevice(); rtnl_unlock(); // LOCKDEP violation rtnl_lock(); I will revisit this in next cycle, opt-in for the new behavior from safe contexts only. Fixes: cfa579f66656 ("net: no longer hold RTNL while calling flush_all_backlogs()") Fixes: ae646f1a0bb9 ("net: reduce RTNL hold duration in unregister_netdevice_many_notify() (part 1)") Fixes: 83419b61d187 ("net: reduce RTNL hold duration in unregister_netdevice_many_notify() (part 2)") Reported-by: syzbot+5b9196ecf74447172a9a@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/6789d55f.050a0220.20d369.004e.GAE@google.com/ Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250129142726.747726-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- net/core/dev.c | 33 +++------------------------------ 1 file changed, 3 insertions(+), 30 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index 02cd75b512f9..c0021cbd28fc 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -10264,37 +10264,14 @@ static bool from_cleanup_net(void) #endif } -static void rtnl_drop_if_cleanup_net(void) -{ - if (from_cleanup_net()) - __rtnl_unlock(); -} - -static void rtnl_acquire_if_cleanup_net(void) -{ - if (from_cleanup_net()) - rtnl_lock(); -} - /* Delayed registration/unregisteration */ LIST_HEAD(net_todo_list); -static LIST_HEAD(net_todo_list_for_cleanup_net); - -/* TODO: net_todo_list/net_todo_list_for_cleanup_net should probably - * be provided by callers, instead of being static, rtnl protected. - */ -static struct list_head *todo_list(void) -{ - return from_cleanup_net() ? &net_todo_list_for_cleanup_net : - &net_todo_list; -} - DECLARE_WAIT_QUEUE_HEAD(netdev_unregistering_wq); atomic_t dev_unreg_count = ATOMIC_INIT(0); static void net_set_todo(struct net_device *dev) { - list_add_tail(&dev->todo_list, todo_list()); + list_add_tail(&dev->todo_list, &net_todo_list); } static netdev_features_t netdev_sync_upper_features(struct net_device *lower, @@ -11144,7 +11121,7 @@ void netdev_run_todo(void) #endif /* Snapshot list, allow later requests */ - list_replace_init(todo_list(), &list); + list_replace_init(&net_todo_list, &list); __rtnl_unlock(); @@ -11789,11 +11766,9 @@ void unregister_netdevice_many_notify(struct list_head *head, WRITE_ONCE(dev->reg_state, NETREG_UNREGISTERING); netdev_unlock(dev); } - - rtnl_drop_if_cleanup_net(); flush_all_backlogs(); + synchronize_net(); - rtnl_acquire_if_cleanup_net(); list_for_each_entry(dev, head, unreg_list) { struct sk_buff *skb = NULL; @@ -11853,9 +11828,7 @@ void unregister_netdevice_many_notify(struct list_head *head, #endif } - rtnl_drop_if_cleanup_net(); synchronize_net(); - rtnl_acquire_if_cleanup_net(); list_for_each_entry(dev, head, unreg_list) { netdev_put(dev, &dev->dev_registered_tracker);