linux-kernel - Re: "tuntap: multiqueue support" causes udev fork bombs

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Date:	Fri, 30 Nov 2012 18:01:29 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Jason Wang <jasowang@...hat.com>
CC:	"David S. Miller" <davem@...emloft.net>,
	ML netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, rmilasan@...e.cz,
	Jiri Slaby <jirislaby@...il.com>, maxk@...lcomm.com,
	vtun@...ice.satix.net
Subject: Re: "tuntap: multiqueue support" causes udev fork bombs

On 11/29/2012 06:47 AM, Jason Wang wrote:
> On Wednesday, November 28, 2012 11:25:41 AM Jiri Slaby wrote:
>> Hi,
>>
>> with this commit:
>> commit c8d68e6be1c3b242f1c598595830890b65cea64a
>> Author: Jason Wang <jasowang@...hat.com>
>> Date:   Wed Oct 31 19:46:00 2012 +0000
>>
>>     tuntap: multiqueue support
>>
>>
>> I see fork bombs from udev. It is trying to create 2048 processes. 1024
>> for tx, 1024 for rx. OOM killer indeed steps in and kills everything.
> 
> Hi, thanks for the reporting, could you pls try the following patch?

Hi, it is gone with this patch.

> ---
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index b44d7b7..cc3f878 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -492,9 +492,6 @@ static int tun_attach(struct tun_struct *tun, struct file *file)
>  
>  	tun_set_real_num_queues(tun);
>  
> -	if (tun->numqueues == 1)
> -		netif_carrier_on(tun->dev);
> -
>  	/* device is allowed to go away first, so no need to hold extra
>  	 * refcnt.
>  	 */
> @@ -1611,6 +1608,10 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
>  			TUN_USER_FEATURES;
>  		dev->features = dev->hw_features;
>  
> +		err = tun_attach(tun, file);
> +		if (err < 0)
> +			goto err_free_dev;
> +
>  		err = register_netdevice(tun->dev);
>  		if (err < 0)
>  			goto err_free_dev;
> @@ -1620,9 +1621,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
>  		    device_create_file(&tun->dev->dev, &dev_attr_group))
>  			pr_err("Failed to create tun sysfs files\n");
>  
> -		err = tun_attach(tun, file);
> -		if (err < 0)
> -			goto err_free_dev;
> +		netif_carrier_on(tun->dev);
>  	}
>  
>  	tun_debug(KERN_INFO, tun, "tun_set_iff\n");
> 


-- 
js
suse labs
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