Re: [PATCH][NET_SCHED] cls_u32: refcounting fix for u32_delete()

[Jarek Poplawski <jarkao2@gmail.com>]

On Fri, Apr 11, 2008 at 02:55:27PM +0200, Patrick McHardy wrote:
> Jarek Poplawski wrote:
>> [NET_SCHED] cls_u32: refcounting fix for u32_delete()
>>
>> @@ -441,8 +443,10 @@ static int u32_delete(struct tcf_proto *tp, unsigned long arg)
>>  	if (tp->root == ht)
>>  		return -EINVAL;
>>  -	if (--ht->refcnt == 0)
>> +	if (ht->refcnt == 1) {
>> +		ht->refcnt--;
>>  		u32_destroy_hnode(tp, ht);
>> +	}
>>  
>
> Shouldn't the refcount be decremented unconditionally?
> Otherwise I'd suggest to reject the removal if refcnt > 1,
> but silently doing nothing doesn't seem right.

If someone tries deleting and the refcnt is e.g. 3 (2 links)
unconditional deleting could decrease refcnt without deleting
and then unlinking would make it below 0. I think it's OK now:
we can't delete hnode until it's referenced, but I could add
a warning if you like?

Thanks,
Jarek P.