netdev - Re: [PATCH 1/2] cfg80211: fix dead lock for nl80211_new

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Date:   Wed, 21 Sep 2022 18:36:18 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Aran Dalton <arda@...winnertech.com>, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] cfg80211: fix dead lock for nl80211_new_interface()

On Wed, 2022-09-21 at 17:19 +0800, Aran Dalton wrote:
> Both nl80211_new_interface and cfg80211_netdev_notifier_call hold the
> same wiphy_lock, then cause deadlock.
> 
> The main call stack as bellow:
> 
> nl80211_new_interface() takes wiphy_lock
>  -> _nl80211_new_interface:
>   -> rdev_add_virtual_intf
>    -> rdev->ops->add_virtual_intf
>     -> register_netdevice

The bug is yours, here, you're no longer allowed to call
register_netdevice() here.

If you have an out-of-tree driver that we couldn't update when doing
tree-wide changes, you probably shouldn't assume that the bug is
upstream and send random locking patches ... :)

johannes