netdev - Re: [PATCH for 2.6.33] conntrack: restrict runtime hashsize modifications

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Date:	Thu, 04 Feb 2010 18:26:45 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Alexey Dobriyan <adobriyan@...il.com>
CC:	davem@...emloft.net, jonathan@...masters.org,
	eric.dumazet@...il.com, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org
Subject: Re: [PATCH for 2.6.33] conntrack: restrict runtime hashsize modifications

Alexey Dobriyan wrote:
> Jon Masters correctly points out that conntrack hash sizes
> (nf_conntrack_htable_size) are global (not per-netns) and
> modifiable at runtime via /sys/module/nf_conntrack/hashsize .
> 
> Steps to reproduce:
> 	clone(CLONE_NEWNET)
> 	[grow /sys/module/nf_conntrack/hashsize]
> 	exit()
> 
> At netns exit we are going to scan random memory for conntracks to be killed.
> 
> Apparently there is a code which deals with hashtable resize for
> init_net (and it was there befode netns conntrack code), so prohibit
> hashsize modification if there is more than one netns exists.
> 
> To change hashtable sizes, you need to reload module.
> 
> Expectation hashtable size was simply glued to a variable with no code
> to rehash expectations, so it was a bug to allow writing to it.
> Make "expect_hashsize" readonly.

I've applied the expectation part, thanks Alexey.

> --- a/net/netfilter/nf_conntrack_expect.c
> +++ b/net/netfilter/nf_conntrack_expect.c
> @@ -569,7 +569,7 @@ static void exp_proc_remove(struct net *net)
>  #endif /* CONFIG_PROC_FS */
>  }
>  
> -module_param_named(expect_hashsize, nf_ct_expect_hsize, uint, 0600);
> +module_param_named(expect_hashsize, nf_ct_expect_hsize, uint, 0400);
>  
>  int nf_conntrack_expect_init(struct net *net)
>  {
> 

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