netdev - Re: [PATCH 3.8-rc] tuntap: refuse to re-attach to different tun

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Date:	Thu, 10 Jan 2013 17:25:45 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	Stefan Hajnoczi <stefanha@...hat.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	"Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3.8-rc] tuntap: refuse to re-attach to different tun_struct

On Thursday, January 10, 2013 08:59:48 AM Stefan Hajnoczi wrote:
> Multiqueue tun devices support detaching a tun_file from its tun_struct
> and re-attaching at a later point in time.  This allows users to disable
> a specific queue temporarily.
> 
> ioctl(TUNSETIFF) allows the user to specify the network interface to
> attach by name.  This means the user can attempt to attach to interface
> "B" after detaching from interface "A".
> 
> The driver is not designed to support this so check we are re-attaching
> to the right tun_struct.  Failure to do so may lead to oops.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@...hat.com>
> ---
> This fix is for 3.8-rc.
> 
>  drivers/net/tun.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index fbd106e..cf6da6e 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -491,6 +491,8 @@ static int tun_attach(struct tun_struct *tun, struct
> file *file) err = -EINVAL;
>  	if (rcu_dereference_protected(tfile->tun, lockdep_rtnl_is_held()))
>  		goto out;
> +	if (tfile->detached && tun != tfile->detached)
> +		goto out;
> 
>  	err = -EBUSY;
>  	if (!(tun->flags & TUN_TAP_MQ) && tun->numqueues == 1)

Thanks.

Acked-by: Jason Wang <jasowang@...hat.com>

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