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:	Tue, 22 Jul 2014 10:42:14 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Julian Anastasov <ja@....bg>
Cc:	Andrey Utkin <andrey.krieger.utkin@...il.com>,
	"linux-kernel@...r.kernel.org" <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,
	David Miller <davem@...emloft.net>, kadlec@...ckhole.kfki.hu,
	Patrick McHardy <kaber@...sh.net>, pablo@...filter.org,
	Simon Horman <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

On Mon, Jul 21, 2014 at 11:01:56PM +0300, Julian Anastasov wrote:
> @@ -2333,13 +2339,12 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
>  	struct ip_vs_dest_user_kern udest;
>  	struct netns_ipvs *ipvs = net_ipvs(net);
>  
> +	BUILD_BUG_ON(sizeof(arg) > 256);

256 is off-by-one because u8 ranges from 0-255 so we are never able to
copy 256 bytes into the "arg" buffer.

> -	if (copylen > 128)
> +	if (*len < (int) copylen || *len < 0) {
> +		pr_err("get_ctl: len %d < %u\n", *len, copylen);

Don't let users flood dmesg.  Just return an error.  (This can be
triggered by non-root as well).

>  		return -EINVAL;
> +	}

regards,
dan carpenter
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