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References: <cover.1647255926.git.william.xuanziyang@huawei.com> <751f88c0846df798a403643cefcaab53922ffe2f.1647255926.git.william.xuanziyang@huawei.com>
In-Reply-To: <751f88c0846df798a403643cefcaab53922ffe2f.1647255926.git.william.xuanziyang@huawei.com>
From:   Eric Dumazet <edumazet@google.com>
Date:   Mon, 14 Mar 2022 10:24:01 -0700
Message-ID: <CANn89iLK9theyFtU+++UQNHc-cn5cTz-Q_CP3BY44WBbfQfS8g@mail.gmail.com>
Subject: Re: [PATCH net-next 1/3] net: ipvlan: fix potential UAF problem for phy_dev
To:     Ziyang Xuan <william.xuanziyang@huawei.com>
Cc:     David Miller <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        netdev <netdev@vger.kernel.org>, sakiwit@gmail.com,
        LKML <linux-kernel@vger.kernel.org>
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On Mon, Mar 14, 2022 at 3:54 AM Ziyang Xuan
<william.xuanziyang@huawei.com> wrote:
>
> Add the reference operation to phy_dev of ipvlan to avoid
> the potential UAF problem under the following known scenario:
>
> Someone module puts the NETDEV_UNREGISTER event handler to a
> work, and phy_dev is accessed in the work handler. But when
> the work is excuted, phy_dev has been destroyed because upper
> ipvlan did not get reference to phy_dev correctly.

Can you name the module deferring NETDEV_UNREGISTER to a work queue ?

This sounds like a bug to me.

>
> That likes as the scenario occurred by
> commit 563bcbae3ba2 ("net: vlan: fix a UAF in vlan_dev_real_dev()").

Mentioning a commit that added a bug and many other commits trying to
fix it is a bit unfortunate.

Can you instead add a Fixes: tag ?

Do you have a repro to trigger the bug ?

>
> Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
> ---
>  drivers/net/ipvlan/ipvlan_main.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/drivers/net/ipvlan/ipvlan_main.c b/drivers/net/ipvlan/ipvlan_main.c
> index 696e245f6d00..dcdc01403f22 100644
> --- a/drivers/net/ipvlan/ipvlan_main.c
> +++ b/drivers/net/ipvlan/ipvlan_main.c
> @@ -158,6 +158,10 @@ static int ipvlan_init(struct net_device *dev)
>         }
>         port = ipvlan_port_get_rtnl(phy_dev);
>         port->count += 1;
> +
> +       /* Get ipvlan's reference to phy_dev */
> +       dev_hold(phy_dev);
> +
>         return 0;
>  }
>
> @@ -665,6 +669,14 @@ void ipvlan_link_delete(struct net_device *dev, struct list_head *head)
>  }
>  EXPORT_SYMBOL_GPL(ipvlan_link_delete);
>
> +static void ipvlan_dev_free(struct net_device *dev)
> +{
> +       struct ipvl_dev *ipvlan = netdev_priv(dev);
> +
> +       /* Get rid of the ipvlan's reference to phy_dev */
> +       dev_put(ipvlan->phy_dev);
> +}
> +
>  void ipvlan_link_setup(struct net_device *dev)
>  {
>         ether_setup(dev);
> @@ -674,6 +686,7 @@ void ipvlan_link_setup(struct net_device *dev)
>         dev->priv_flags |= IFF_UNICAST_FLT | IFF_NO_QUEUE;
>         dev->netdev_ops = &ipvlan_netdev_ops;
>         dev->needs_free_netdev = true;
> +       dev->priv_destructor = ipvlan_dev_free;
>         dev->header_ops = &ipvlan_header_ops;
>         dev->ethtool_ops = &ipvlan_ethtool_ops;
>  }
> --
> 2.25.1
>