netdev - Re: [PATCH 00/16] Remove the ipv4 routing cache

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20120726.011853.973075299731735416.davem@davemloft.net>
Date:	Thu, 26 Jul 2012 01:18:53 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	alexander.duyck@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH 00/16] Remove the ipv4 routing cache

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Thu, 26 Jul 2012 10:13:34 +0200

> On Wed, 2012-07-25 at 17:54 -0700, David Miller wrote:
>> @@ -1216,9 +1215,15 @@ static void rt_cache_route(struct fib_nh *nh, struct rtable *rt)
>>  
>>  	prev = cmpxchg(p, orig, rt);
>>  	if (prev == orig) {
>> -		dst_clone(&rt->dst);
>>  		if (orig)
>> -			call_rcu_bh(&orig->dst.rcu_head, rt_release_rcu);
>> +			rt_free(orig);
>> +	} else {
>> +		/* Routes we intend to cache in the FIB nexthop have
>> +		 * the DST_NOCACHE bit set.  However, if we are
>> +		 * unsuccessful at storing this route into the cache
>> +		 * we really need to clear that bit.
>> +		 */
>> +		rt->dst.flags &= ~DST_NOCACHE;
>>  	}
>>  }
>>  
> 
> Not sure why you removed the dst_clone(&rt->dst) ?

Because "cached" dst objects have no reference count.  When such a
cached dst is "released", it is dst_free()'d instead of
dst_release()'d.

> If it is not needed, we might need to release a reference in the else {}
> clause, no ?

Nope.  'rt' has a reference count of one, which is for the caller, not
for this cached location.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html