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From:   Cong Wang <xiyou.wangcong@gmail.com>
Date:   Mon, 12 Mar 2018 16:17:23 -0700
Message-ID: <CAM_iQpVWQ+4YKX=ZCCpJ3fzbexNVYJ8wONz9QnwuxBtbQwx3Lg@mail.gmail.com>
Subject: Re: [PATCH 1/1] net: check dev->reg_state before deref of napi netdev_ops
To:     Josh Elsasser <jelsasser@appneta.com>
Cc:     David Miller <davem@davemloft.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Eric Dumazet <edumazet@google.com>,
        Sasha Levin <alexander.levin@verizon.com>,
        Willem de Bruijn <willemb@google.com>,
        Alexander Potapenko <glider@google.com>,
        =?UTF-8?Q?Michal_Kube=C4=8Dek?= <mkubecek@suse.cz>,
        Linux Kernel Network Developers <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Sun, Mar 11, 2018 at 12:22 PM, Josh Elsasser <jelsasser@appneta.com> wrote:
> init_dummy_netdev() leaves its netdev_ops pointer zeroed. This leads
> to a NULL pointer dereference when sk_busy_loop fires against an iwlwifi
> wireless adapter and checks napi->dev->netdev_ops->ndo_busy_poll.
>
> Avoid this by ensuring that napi->dev is not a dummy device before
> dereferencing napi dev's netdev_ops, preventing the following panic:

Hmm, how about just checking ->netdev_ops? Checking reg_state looks
odd, although works.