linux-kernel - Re: [PATCH] netfilter: replace horrible hack with ksize()

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Date:	Thu, 06 Mar 2008 15:03:35 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Pekka J Enberg <penberg@...helsinki.fi>
CC:	netfilter-devel@...r.kernel.org, clameter@....com, joe@...ches.com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Netfilter Development Mailinglist 
	<netfilter-devel@...r.kernel.org>
Subject: Re: [PATCH] netfilter: replace horrible hack with ksize()

Pekka J Enberg wrote:
> From: Pekka Enberg <penberg@...helsinki.fi>
> 
> There's a horrible slab abuse in net/netfilter/nf_conntrack_extend.c that 
> can be replaced with a call to ksize().

This doesn't look right.

> @@ -95,7 +85,7 @@ void *__nf_ct_ext_add(struct nf_conn *ct
>  	newlen = newoff + t->len;
>  	rcu_read_unlock();
>  
> -	if (newlen >= ct->ext->real_len) {
> +	if (newlen >= ksize(ct->ext)) {


This needs to look at the currently allocated size, otherwise
it will always realloc when adding new extensions after having
used up ksize(ct->ext) space.

>  		new = kmalloc(newlen, gfp);

And this should use ksize(newlen) and store the real length
in real_len below.

>  		if (!new)
>  			return NULL;
> @@ -114,7 +104,6 @@ void *__nf_ct_ext_add(struct nf_conn *ct
>  			rcu_read_unlock();
>  		}
>  		kfree(ct->ext);
> -		new->real_len = newlen;
>  		ct->ext = new;
>  	}

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