[PATCH 5.10 011/105] net: make sure devices go through netdev_wait_all_refs

Greg Kroah-Hartman
2022-07-27T16:48:04Z

From: Fedor Pchelkin <pchelkin@ispras.ru>

From: Jakub Kicinski <kuba@kernel.org>

commit 766b0515d5bec4b780750773ed3009b148df8c0a upstream.

If register_netdevice() fails at the very last stage - the
notifier call - some subsystems may have already seen it and
grabbed a reference. struct net_device can't be freed right
away without calling netdev_wait_all_refs().

Now that we have a clean interface in form of dev->needs_free_netdev
and lenient free_netdev() we can undo what commit 93ee31f14f6f ("[NET]:
Fix free_netdev on register_netdev failure.") has done and complete
the unregistration path by bringing the net_set_todo() call back.

After registration fails user is still expected to explicitly
free the net_device, so make sure ->needs_free_netdev is cleared,
otherwise rolling back the registration will cause the old double
free for callers who release rtnl_lock before the free.

This also solves the problem of priv_destructor not being called
on notifier error.

net_set_todo() will be moved back into unregister_netdevice_queue()
in a follow up.

Reported-by: Hulk Robot <hulkci@huawei.com>
Reported-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/core/dev.c | 14 ++++----------
1 file changed, 4 insertions(+), 10 deletions(-)

--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10144,17 +10144,11 @@ int register_netdevice(struct net_device
ret = call_netdevice_notifiers(NETDEV_REGISTER, dev);
ret = notifier_to_errno(ret);
if (ret) {
+ /* Expect explicit free_netdev() on failure */
+ dev->needs_free_netdev = false;
rollback_registered(dev);
- rcu_barrier();
-
- dev->reg_state = NETREG_UNREGISTERED;
- /* We should put the kobject that hold in
- * netdev_unregister_kobject(), otherwise
- * the net device cannot be freed when
- * driver calls free_netdev(), because the
- * kobject is being hold.
- */
- kobject_put(&dev->dev.kobj);
+ net_set_todo(dev);
+ goto out;
}
/*
* Prevent userspace races by waiting until the network