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net: make sure devices go through netdev_wait_all_refs

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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 93ee31f14f ("[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>
This commit is contained in:
Jakub Kicinski 2021-01-06 10:40:07 -08:00
parent c269a24ce0
commit 766b0515d5
1 changed files with 4 additions and 10 deletions
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14
net/core/dev.c
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@ -10077,17 +10077,11 @@ int register_netdevice(struct net_device *dev)
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