linux-kernel - Re: [PATCH net] net: dev: Detect dev_hold() after netdev_wait

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Message-ID: <20220127182219.1da582f6@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Thu, 27 Jan 2022 18:22:19 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Jann Horn <jannh@...gle.com>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Oliver Neukum <oneukum@...e.com>
Subject: Re: [PATCH net] net: dev: Detect dev_hold() after
 netdev_wait_allrefs()

On Fri, 28 Jan 2022 03:14:14 +0100 Jann Horn wrote:
> Oh. Whoops. That's what I get for only testing without CONFIG_PCPU_DEV_REFCNT...
> 
> I guess a better place to put the new check would be directly after
> checking for "dev->reg_state == NETREG_UNREGISTERING"? Like this?

Possibly a very silly suggestion but perhaps we should set 
the pointer to NULL for the pcpu case and let it crash?