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Subject: Re: [BUG] deadlock in nl80211_vendor_cmd
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Jakub Kicinski <kuba@kernel.org>
Cc:     William McVicker <willmcvicker@google.com>,
        linux-wireless@vger.kernel.org,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        "David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org,
        Amitkumar Karwar <amitkarwar@gmail.com>,
        Xinming Hu <huxinming820@gmail.com>, kernel-team@android.com,
        Paolo Abeni <pabeni@redhat.com>,
        Eric Dumazet <edumazet@google.com>,
        Cong Wang <cwang@twopensource.com>,
        Cong Wang <xiyou.wangcong@gmail.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>
Date:   Fri, 25 Mar 2022 22:50:02 +0100
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On Fri, 2022-03-25 at 14:48 -0700, Jakub Kicinski wrote:
> > 
> > > The WARN_ON() you suggested up front make perfect sense to me.
> > > You can also take the definition of net_unlink_todo() out of
> > > netdevice.h while at it because o_0  
> > 
> > Heh indeed, what?
> 
> To be clear - I just meant that it's declaring a static variable in 
> a header, so I doubt that it'll do the right thing unless it's only
> called from one compilation unit.

Right, it's odd. I just made a patch (will send in a minute) moving the
entire block to dev.c, which is the only user of any of it.

> > Ah, no. This isn't about locking in this case, it's literally about
> > ensuring that free_netdev() has been called in netdev_run_todo()?
> 
> Yup, multiple contexts sitting independently in netdev_run_todo() and
> chewing on netdevs is slightly different. destructors of those netdevs
> could be pointing at memory of a module being unloaded.

Right, thanks.

johannes