netdev - Re: [PATCH] ipv4: netfilter: ipt_CLUSTERIP: fix buffer overflow

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Message-ID: <AANLkTimPZJoCzz386e-4m0Y4khWGZirZguGFmuFYCrry@mail.gmail.com>
Date:	Sun, 13 Mar 2011 22:00:03 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Vasiliy Kulikov <segoon@...nwall.com>
Cc:	linux-kernel@...r.kernel.org, security@...nel.org,
	Patrick McHardy <kaber@...sh.net>,
	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	netfilter-devel@...r.kernel.org, netfilter@...r.kernel.org,
	coreteam@...filter.org, netdev@...r.kernel.org
Subject: Re: [PATCH] ipv4: netfilter: ipt_CLUSTERIP: fix buffer overflow

On Fri, Mar 11, 2011 at 2:12 AM, Vasiliy Kulikov <segoon@...nwall.com> wrote:
> buffer string is copied from userspace.  It is not checked whether it is
> zero terminated.  This may lead to overflow inside of simple_strtoul().
>
> It was introduced before the git epoch.  Files "ipt_CLUSTERIP/*" are
> root writable only by default, however, on some setups permissions might be
> relaxed to e.g. network admin user.
>
> Signed-off-by: Vasiliy Kulikov <segoon@...nwall.com>
> ---
>  Compile tested.
>
>  net/ipv4/netfilter/ipt_CLUSTERIP.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c
> index 403ca57..7aabf9a 100644
> --- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
> +++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
> @@ -666,6 +666,7 @@ static ssize_t clusterip_proc_write(struct file *file, const char __user *input,
>
>        if (copy_from_user(buffer, input, PROC_WRITELEN))

I think size should be used instead of PROC_WRITELEN.

if (size > PROC_WRITELEN)
     return -EIO;
if (copy_from_user(buffer, input, size))
    return -EFAULT;
buffer[size] = '\0';

>                return -EFAULT;
> +       buffer[sizeof(buffer)-1] = 0;
>
>        if (*buffer == '+') {
>                nodenum = simple_strtoul(buffer+1, NULL, 10);



-- 
Regards,
Changli Gao(xiaosuo@...il.com)
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