Re: [PATCH] ulog: add protection when remove ipt_ULOG

[Pablo Neira Ayuso <pablo@netfilter.org>]

Hi Gao,

On Tue, Feb 05, 2013 at 09:57:30AM +0800, Gao feng wrote:
> We should add a lock protection when we free the skb,
> because it maybe used by ipt_ulog_packet right now.

Did you hit a reproducible crash?

I think this is very unlikely to happen. The removal of the module
happens in user-context and the entire path to build and deliver the
skb to user-space is protected is under spin_lock_bh, so scheduling
is not possible.

> Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
> ---
>  net/ipv4/netfilter/ipt_ULOG.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/ipv4/netfilter/ipt_ULOG.c b/net/ipv4/netfilter/ipt_ULOG.c
> index b5ef3cb..b390002 100644
> --- a/net/ipv4/netfilter/ipt_ULOG.c
> +++ b/net/ipv4/netfilter/ipt_ULOG.c
> @@ -430,11 +430,12 @@ static void __exit ulog_tg_exit(void)
>  			pr_debug("timer was pending, deleting\n");
>  			del_timer(&ub->timer);
>  		}
> -
> +		spin_lock_bh(&ulog_lock);
>  		if (ub->skb) {
>  			kfree_skb(ub->skb);
>  			ub->skb = NULL;
>  		}
> +		spin_unlock_bh(&ulog_lock);
>  	}
>  }
>  
> -- 
> 1.7.11.7
> 
> --
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