netdev - Re: [PATCH net-next] macvlan: fix failure during registration v3

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Message-ID: <CAF2d9jh98MGYorJ=btvx04==EsjP5_ivUEimf0TJ1NUPDzG4nw@mail.gmail.com>
Date:	Tue, 26 Apr 2016 11:54:08 -0700
From:	Mahesh Bandewar <maheshb@...gle.com>
To:	Francesco Ruggeri <fruggeri@...sta.com>
Cc:	linux-netdev <netdev@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH net-next] macvlan: fix failure during registration v3

On Sat, Apr 23, 2016 at 3:03 PM, Francesco Ruggeri <fruggeri@...sta.com> wrote:
> If macvlan_common_newlink fails in register_netdevice after macvlan_init
> then it decrements port->count twice, first in macvlan_uninit (from
> register_netdevice or rollback_registered) and then again in
> macvlan_common_newlink.
> A similar problem may exist in the ipvlan driver.
That is correct! The problem exists in ipvlan driver also. I'll cook a
patch to fix this in ipvlan driver.

> This patch consolidates modifications to port->count into macvlan_init
> and macvlan_uninit (thanks to Eric Biederman for suggesting this approach).
>
> v3: remove macvtap specific bits.
>
> Signed-off-by: Francesco Ruggeri <fruggeri@...sta.com>
> ---
>  drivers/net/macvlan.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
> index 2bcf1f3..cb01023 100644
> --- a/drivers/net/macvlan.c
> +++ b/drivers/net/macvlan.c
> @@ -795,6 +795,7 @@ static int macvlan_init(struct net_device *dev)
>  {
>         struct macvlan_dev *vlan = netdev_priv(dev);
>         const struct net_device *lowerdev = vlan->lowerdev;
> +       struct macvlan_port *port = vlan->port;
>
>         dev->state              = (dev->state & ~MACVLAN_STATE_MASK) |
>                                   (lowerdev->state & MACVLAN_STATE_MASK);
> @@ -812,6 +813,8 @@ static int macvlan_init(struct net_device *dev)
>         if (!vlan->pcpu_stats)
>                 return -ENOMEM;
>
> +       port->count += 1;
> +
>         return 0;
>  }
>
> @@ -1312,10 +1315,9 @@ int macvlan_common_newlink(struct net *src_net, struct net_device *dev,
>                         return err;
>         }
>
> -       port->count += 1;
>         err = register_netdevice(dev);
>         if (err < 0)
> -               goto destroy_port;
> +               return err;
>
>         dev->priv_flags |= IFF_MACVLAN;
>         err = netdev_upper_dev_link(lowerdev, dev);
> @@ -1330,10 +1332,6 @@ int macvlan_common_newlink(struct net *src_net, struct net_device *dev,
>
>  unregister_netdev:
>         unregister_netdevice(dev);
> -destroy_port:
> -       port->count -= 1;
> -       if (!port->count)
> -               macvlan_port_destroy(lowerdev);
I think you still need this when it fails netdev_upper_dev_link(). The
only thing you should remove is the label.
>
>         return err;
>  }
> --
> 1.8.1.4
>