linux-kernel - Re: [PATCH] can: gw: Fix error path of cgw_module

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Date:   Fri, 17 May 2019 12:40:28 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     YueHaibing <yuehaibing@...wei.com>, davem@...emloft.net,
        socketcan@...tkopp.net
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        linux-can@...r.kernel.org
Subject: Re: [PATCH] can: gw: Fix error path of cgw_module_init

On 5/16/19 5:54 PM, YueHaibing wrote:
> This patch fix error path for cgw_module_init
> to avoid possible crash if some error occurs.
> 
> Fixes: c1aabdf379bc ("can-gw: add netlink based CAN routing")
> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> ---
>  net/can/gw.c | 46 +++++++++++++++++++++++++++++++---------------
>  1 file changed, 31 insertions(+), 15 deletions(-)
> 
> diff --git a/net/can/gw.c b/net/can/gw.c
> index 53859346..8b53ec7 100644
> --- a/net/can/gw.c
> +++ b/net/can/gw.c
> @@ -1046,32 +1046,48 @@ static __init int cgw_module_init(void)
>  	pr_info("can: netlink gateway (rev " CAN_GW_VERSION ") max_hops=%d\n",
>  		max_hops);
>  
> -	register_pernet_subsys(&cangw_pernet_ops);
> +	ret = register_pernet_subsys(&cangw_pernet_ops);
> +	if (ret)
> +		return ret;
> +
> +	ret = -ENOMEM;
>  	cgw_cache = kmem_cache_create("can_gw", sizeof(struct cgw_job),
>  				      0, 0, NULL);
> -
>  	if (!cgw_cache)
> -		return -ENOMEM;
> +		goto out_cache_create;
>  
>  	/* set notifier */
>  	notifier.notifier_call = cgw_notifier;
> -	register_netdevice_notifier(&notifier);
> +	ret = register_netdevice_notifier(&notifier);
> +	if (ret)
> +		goto out_register_notifier;
>  
>  	ret = rtnl_register_module(THIS_MODULE, PF_CAN, RTM_GETROUTE,
>  				   NULL, cgw_dump_jobs, 0);
> -	if (ret) {
> -		unregister_netdevice_notifier(&notifier);
> -		kmem_cache_destroy(cgw_cache);
> -		return -ENOBUFS;
> -	}
> -
> -	/* Only the first call to rtnl_register_module can fail */
> -	rtnl_register_module(THIS_MODULE, PF_CAN, RTM_NEWROUTE,
> -			     cgw_create_job, NULL, 0);
> -	rtnl_register_module(THIS_MODULE, PF_CAN, RTM_DELROUTE,
> -			     cgw_remove_job, NULL, 0);
> +	if (ret)
> +		goto out_rtnl_register1;
> +
> +	ret = rtnl_register_module(THIS_MODULE, PF_CAN, RTM_NEWROUTE,
> +				   cgw_create_job, NULL, 0);
> +	if (ret)
> +		goto out_rtnl_register2;
> +	ret = rtnl_register_module(THIS_MODULE, PF_CAN, RTM_DELROUTE,
> +				   cgw_remove_job, NULL, 0);
> +	if (ret)
> +		goto out_rtnl_register2;
>  
>  	return 0;
> +
> +out_rtnl_register2:
> +	rtnl_unregister_all(PF_CAN);

Currently gw.c is the only user of rtnl_register_module(PF_CAN), but
PF_CAN is not specific to gw. Better change this to individual
rtnl_unregister(int protocol, int msgtype).

> +out_rtnl_register1:
> +	unregister_netdevice_notifier(&notifier);
> +out_register_notifier:
> +	kmem_cache_destroy(cgw_cache);
> +out_cache_create:
> +	unregister_pernet_subsys(&cangw_pernet_ops);
> +
> +	return ret;
>  }
>  
>  static __exit void cgw_module_exit(void)
> 

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
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