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

[Simon Horman <horms@verge.net.au>]

On Tue, Dec 15, 2009 at 05:32:01PM +1100, Simon Horman wrote:
> On Mon, Dec 14, 2009 at 10:17:04PM -0800, Arjan van de Ven wrote:
> > On Wed, 30 Sep 2009 13:11:09 +0200
> > Arjan van de Ven <arjan@infradead.org> wrote:
> > 
> > ping on the patch below.... the warning is now triggered in mainline
> 
> Hi Arjan,
> 
> could you address the comments Julian made about this?
> http://lkml.indiana.edu/hypermail/linux/kernel/0910.0/00852.html
> 
> 	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@ssi.bg>

Ping.

While I agree with Julian that the patch you suggest below
ought not to be necessary, I'm also happy with it if
cmd > IP_VS_SO_SET_MAX + 1 is changed to cmd > IP_VS_SO_SET_MAX.

> > > >From 761a182f96b3707e1fee44e1079ba227e48745d1 Mon Sep 17 00:00:00
> > > >2001
> > > From: Arjan van de Ven <arjan@linux.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@linux.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..3c52796 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 >  MAX_ARG_LEN)
> > > +		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 > 128)
> > > +		return -EINVAL;
> > > +
> > > +	if (copy_from_user(arg, user, copylen) != 0)
> > >  		return -EFAULT;
> > >  
> > >  	if (mutex_lock_interruptible(&__ip_vs_mutex))
> > 
> > 
> > -- 
> > Arjan van de Ven 	Intel Open Source Technology Centre
> > For development, discussion and tips for power savings, 
> > visit http://www.lesswatts.org
> > --
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