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Date: Thu, 24 Dec 2009 15:16:48 +1100
From: Simon Horman <horms@...ge.net.au>
To: Arjan van de Ven <arjan@...radead.org>
Cc: Wensong Zhang <wensong@...ux-vs.org>, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, Julian Anastasov <ja@....bg>
Subject: Re: [PATCH] ipvs: Add boundary check on ioctl arguments
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@...radead.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@....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@...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..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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