linux-kernel - Re: [PATCH 3/5] net/netfilter/ipvs/ip_vs_ctl.c: drop argument range check just before the check for equality

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Date:	Fri, 18 Jul 2014 23:48:07 +0300 (EEST)
From:	Julian Anastasov <ja@....bg>
To:	Andrey Utkin <andrey.krieger.utkin@...il.com>
cc:	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
	coreteam@...filter.org, netfilter-devel@...r.kernel.org,
	lvs-devel@...r.kernel.org, netdev@...r.kernel.org,
	dcb314@...mail.com, davem@...emloft.net, kadlec@...ckhole.kfki.hu,
	kaber@...sh.net, pablo@...filter.org, horms@...ge.net.au,
	wensong@...ux-vs.org
Subject: Re: [PATCH 3/5] net/netfilter/ipvs/ip_vs_ctl.c: drop argument range
 check just before the check for equality


	Hello,

On Fri, 18 Jul 2014, Andrey Utkin wrote:

> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=80601
> Reported-by: David Binderman <dcb314@...mail.com>
> Signed-off-by: Andrey Utkin <andrey.krieger.utkin@...il.com>
> ---
>  net/netfilter/ipvs/ip_vs_ctl.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index 581a658..4ed7b59 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> @@ -2338,8 +2338,6 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
>  
>  	if (cmd < IP_VS_BASE_CTL || cmd > IP_VS_SO_SET_MAX)
>  		return -EINVAL;
> -	if (len < 0 || len >  MAX_ARG_LEN)
> -		return -EINVAL;

	The above check ensures the set_arglen[] value (some
struct size) does not exceed the arg[MAX_ARG_LEN] space. You can check
commit 04bcef2a83f40c ("ipvs: Add boundary check on ioctl arguments")
for more info. Still, check can be reduced to
if (len > MAX_ARG_LEN)... Also, len is unsigned, so len < 0 is
useless even for this reason.

>  	if (len != set_arglen[SET_CMDID(cmd)]) {
>  		pr_err("set_ctl: len %u != %u\n",
>  		       len, set_arglen[SET_CMDID(cmd)]);
> -- 
> 1.8.5.5

Regards

--
Julian Anastasov <ja@....bg>
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