netdev - Re: [PATCH] ipvs: Add boundary check on ioctl arguments

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Date:	Fri, 2 Oct 2009 11:35:56 +0300 (EEST)
From:	Julian Anastasov <ja@....bg>
To:	Arjan van de Ven <arjan@...radead.org>
cc:	Hannes Eder <heder@...gle.com>,
	Wensong Zhang <wensong@...ux-vs.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Simon Horman <horms@...ge.net.au>
Subject: Re: [PATCH] ipvs: Add boundary check on ioctl arguments


	Hello,

On Wed, 30 Sep 2009, Arjan van de Ven wrote:

> fair enough; updated patch below

	OK, you can add my signed-off line after changing
'cmd > ...MAX + 1' to 'cmd > ...MAX' at both
places, nf_sockopt_ops ranges are [optmin ... optmax)

May be comments should be changed because:

- i'm not the author but after ispection we do not see any holes,
we do not want users to upgrade just for this change
- the cmd checks are just to help code checking tools
- the len checks should help programmers (may be BUG_ON is
better, user does not deserve EINVAL for wrong set_arglen/get_arglen).
Checks for *len and len are not needed.

	For example, for len checks this should be enough, before
copy_from_user():

in do_ip_vs_get_ctl check can be
	BUG_ON(get_arglen[GET_CMDID(cmd)] > sizeof(arg));

in do_ip_vs_set_ctl check can be
	BUG_ON(set_arglen[SET_CMDID(cmd)] > sizeof(arg));

Acked-by: Julian Anastasov <ja@....bg>

> >From 28ae217858e683c0c94c02219d46a9a9c87f61c6 Mon Sep 17 00:00:00 2001
> From: Arjan van de Ven <arjan@...ux.intel.com>
> Date: Wed, 30 Sep 2009 13:05:51 +0200
> Subject: [PATCH] ipvs: Add boundary check on ioctl arguments
> 
> The ipvs code has a nifty system for doing the size of ioctl command copies;
> it defines an array with values into which it indexes the cmd to find the
> right length.
> 
> Unfortunately, the ipvs code forgot to check if the cmd was in the range
> that the array provides, allowing for an index outside of the array,
> which then gives a "garbage" result into the length, which then gets
> used for copying into a stack buffer.
> 
> Fix this by adding sanity checks on these as well as the copy size.
> 
> Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>
> ---
>  net/netfilter/ipvs/ip_vs_ctl.c |   14 +++++++++++++-
>  1 files changed, 13 insertions(+), 1 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index ac624e5..7adc876 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> @@ -2077,6 +2077,10 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
>  	if (!capable(CAP_NET_ADMIN))
>  		return -EPERM;
>  
> +	if (cmd < IP_VS_BASE_CTL || cmd > IP_VS_SO_SET_MAX + 1)
> +		return -EINVAL;
> +	if (len < 0 || len >  sizeof(arg))
> +		return -EINVAL;
>  	if (len != set_arglen[SET_CMDID(cmd)]) {
>  		pr_err("set_ctl: len %u != %u\n",
>  		       len, set_arglen[SET_CMDID(cmd)]);
> @@ -2353,17 +2357,25 @@ do_ip_vs_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
>  {
>  	unsigned char arg[128];
>  	int ret = 0;
> +	unsigned int copylen;
>  
>  	if (!capable(CAP_NET_ADMIN))
>  		return -EPERM;
>  
> +	if (cmd < IP_VS_BASE_CTL || cmd > IP_VS_SO_GET_MAX + 1)
> +		return -EINVAL;
> +
>  	if (*len < get_arglen[GET_CMDID(cmd)]) {
>  		pr_err("get_ctl: len %u < %u\n",
>  		       *len, get_arglen[GET_CMDID(cmd)]);
>  		return -EINVAL;
>  	}
>  
> -	if (copy_from_user(arg, user, get_arglen[GET_CMDID(cmd)]) != 0)
> +	copylen = get_arglen[GET_CMDID(cmd)];
> +	if (copylen > sizeof(arg))
> +		return -EINVAL;
> +
> +	if (copy_from_user(arg, user, copylen) != 0)
>  		return -EFAULT;
>  
>  	if (mutex_lock_interruptible(&__ip_vs_mutex))

Regards

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