netdev - Re: [PATCH 03/11] net: devres: relax devm_register

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Message-ID: <20200622154943.02782b5a@kicinski-fedora-PC1C0HJN>
Date:   Mon, 22 Jun 2020 15:49:43 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Jonathan Corbet <corbet@....net>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        "David S . Miller" <davem@...emloft.net>,
        John Crispin <john@...ozen.org>,
        Sean Wang <sean.wang@...iatek.com>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Realtek linux nic maintainers <nic_swsd@...ltek.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, devicetree@...r.kernel.org,
        Fabien Parent <fparent@...libre.com>,
        Stephane Le Provost <stephane.leprovost@...iatek.com>,
        Pedro Tsai <pedro.tsai@...iatek.com>,
        Andrew Perepech <andrew.perepech@...iatek.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH 03/11] net: devres: relax devm_register_netdev()

On Mon, 22 Jun 2020 12:00:48 +0200 Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> 
> This devres helper registers a release callback that only unregisters
> the net_device. It works perfectly fine with netdev structs that are
> not managed on their own. There's no reason to check this - drop the
> warning.
> 
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>

I think the reasoning for this suggestion was to catch possible UAF
errors. The netdev doesn't necessarily has to be from devm_alloc_* 
but it has to be part of devm-ed memory or memory which is freed 
after driver's remove callback.

Are there cases in practice where you've seen the netdev not being
devm allocated?