[Devel] [PATCH 1/2] vznetstat: Add protection to venet_acct_set_classes()

[Andrey Ryabinin]

On 12/20/2017 12:30 PM, Kirill Tkhai wrote:

>> How you about this?
>>
> vznetstat: Add protection to venet_acct_set_classes()
> 
> It seems there was no synchronization since the time
> when ioctls in kernel were serialized via single mutex.
> 
> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> ---


Acked-by: Andrey Ryabinin <aryabinin at virtuozzo.com>


> diff --git a/kernel/ve/vznetstat/vznetstat.c b/kernel/ve/vznetstat/vznetstat.c
> index 3a53ce27bde2..92541dbc2a3f 100644
> --- a/kernel/ve/vznetstat/vznetstat.c
> +++ b/kernel/ve/vznetstat/vznetstat.c
> @@ -88,15 +88,11 @@ static int venet_acct_set_classes(const void __user *user_info, int length, int
>  			goto out_free;
>  	}
>  
> -	rcu_read_lock();
> -	if (v6) {
> -		old = rcu_dereference(info_v6);
> -		rcu_assign_pointer(info_v6, info);
> -	} else {
> -		old = rcu_dereference(info_v4);
> -		rcu_assign_pointer(info_v4, info);
> -	}
> -	rcu_read_unlock();
> +	if (v6)
> +		old = xchg(&info_v6, info);
> +	else
> +		old = xchg(&info_v4, info);
> +	/* xchg() implies rcu_assign_pointer() barriers */
>  
>  	synchronize_net();
>  	/* IMPORTANT. I think reset of statistics collected should not be
>