netdev - Re: [RFC PATCH net] net: ipv6: make fib6_nh_init properly clean after itself on error

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Date:   Tue, 30 Nov 2021 09:01:31 -0700
From:   David Ahern <dsahern@...il.com>
To:     Ido Schimmel <idosch@...sch.org>,
        Nikolay Aleksandrov <razor@...ckwall.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        Nikolay Aleksandrov <nikolay@...dia.com>
Subject: Re: [RFC PATCH net] net: ipv6: make fib6_nh_init properly clean after
 itself on error

On 11/30/21 5:40 AM, Ido Schimmel wrote:
> On Mon, Nov 29, 2021 at 04:11:51PM +0200, Nikolay Aleksandrov wrote:
>> diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
>> index 5dbd4b5505eb..a7debafe8b90 100644
>> --- a/net/ipv4/nexthop.c
>> +++ b/net/ipv4/nexthop.c
>> @@ -2565,14 +2565,8 @@ static int nh_create_ipv6(struct net *net,  struct nexthop *nh,
>>  	/* sets nh_dev if successful */
>>  	err = ipv6_stub->fib6_nh_init(net, fib6_nh, &fib6_cfg, GFP_KERNEL,
>>  				      extack);
>> -	if (err) {
>> -		/* IPv6 is not enabled, don't call fib6_nh_release */
>> -		if (err == -EAFNOSUPPORT)
>> -			goto out;
>> -		ipv6_stub->fib6_nh_release(fib6_nh);
>> -	} else {
>> +	if (!err)
>>  		nh->nh_flags = fib6_nh->fib_nh_flags;
>> -	}
>>  out:
>>  	return err;
>>  }
> 
> This hunk looks good

agreed, but it should be a no-op now so this should be a net-next
cleanup patch.

> 
>> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
>> index 42d60c76d30a..2107b13cc9ab 100644
>> --- a/net/ipv6/route.c
>> +++ b/net/ipv6/route.c
>> @@ -3635,7 +3635,9 @@ int fib6_nh_init(struct net *net, struct fib6_nh *fib6_nh,
>>  		in6_dev_put(idev);
>>  
>>  	if (err) {
>> -		lwtstate_put(fib6_nh->fib_nh_lws);
>> +		/* check if we failed after fib_nh_common_init() was called */
>> +		if (fib6_nh->nh_common.nhc_pcpu_rth_output)
>> +			fib_nh_common_release(&fib6_nh->nh_common);
>>  		fib6_nh->fib_nh_lws = NULL;
>>  		dev_put(dev);
>>  	}
> 
> Likewise

this is a leak in the current code and should go through -net as a
separate patch.

> 
>> @@ -3822,7 +3824,7 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
>>  	} else {
>>  		err = fib6_nh_init(net, rt->fib6_nh, cfg, gfp_flags, extack);
>>  		if (err)
>> -			goto out;
>> +			goto out_free;
>>  
>>  		fib6_nh = rt->fib6_nh;
>>  
>> @@ -3841,7 +3843,7 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
>>  		if (!ipv6_chk_addr(net, &cfg->fc_prefsrc, dev, 0)) {
>>  			NL_SET_ERR_MSG(extack, "Invalid source address");
>>  			err = -EINVAL;
>> -			goto out;
>> +			goto out_free;
>>  		}
>>  		rt->fib6_prefsrc.addr = cfg->fc_prefsrc;
>>  		rt->fib6_prefsrc.plen = 128;
>> @@ -3849,12 +3851,13 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
>>  		rt->fib6_prefsrc.plen = 0;
>>  
>>  	return rt;
>> -out:
>> -	fib6_info_release(rt);
>> -	return ERR_PTR(err);
>> +
>>  out_free:
>>  	ip_fib_metrics_put(rt->fib6_metrics);
>> +	if (rt->nh)
>> +		nexthop_put(rt->nh);
> 
> Shouldn't this be above ip_fib_metrics_put() given nexthop_get() is
> called after ip_fib_metrics_init() ?
> 
> Also, shouldn't we call fib6_nh_release() if fib6_nh_init() succeeded
> and we failed later?

similarly I think this cleanup is a separate patch.


> 
>>  	kfree(rt);
>> +out:
>>  	return ERR_PTR(err);
>>  }
>>  
>> -- 
>> 2.31.1
>>