netdev - Re: [PATCH net-next 1/2] net: linkwatch: add check for netdevice being present to linkwatch_do

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Date:   Wed, 19 Sep 2018 10:48:44 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        "David S. Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH net-next 1/2] net: linkwatch: add check for netdevice
 being present to linkwatch_do_dev

On Tue, Sep 18, 2018 at 9:56 PM Heiner Kallweit <hkallweit1@...il.com> wrote:
> When bringing down the netdevice (incl. detaching it) and calling
> netif_carrier_off directly or indirectly the latter triggers an
> asynchronous linkwatch event.
> This linkwatch event eventually may fail to access chip registers in
> the ndo_get_stats/ndo_get_stats64 callback because the device isn't
> accessible any longer, see call trace in [0].
>
> To prevent this scenario don't check for IFF_UP only, but also make
> sure that the netdevice is present.
>
> [0] https://lists.openwall.net/netdev/2018/03/15/62
>
> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>

Survived 100 suspend/resume cycles on sh73a0/kzm9g and r8a73a4/ape6evm.

Tested-by: Geert Uytterhoeven <geert+renesas@...der.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds