linux-kernel - Re: [PATCH] Netfilter: Fix integer overflow in net/ipv6/netfilter/ip6

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Date:	Tue, 23 Mar 2010 10:29:53 +0800
From:	Xiaotian Feng <xtfeng@...il.com>
To:	wzt wzt <wzt.wzt@...il.com>
Cc:	Patrick McHardy <kaber@...sh.net>, linux-kernel@...r.kernel.org,
	netfilter-devel@...r.kernel.org
Subject: Re: [PATCH] Netfilter: Fix integer overflow in net/ipv6/netfilter/ip6_tables.c

On Tue, Mar 23, 2010 at 9:34 AM, wzt wzt <wzt.wzt@...il.com> wrote:
>> I can see that the size might cause an overflow in the addition with
>> sizeof(struct ipt_get_entries)
> That's the integer overflow i pointed.
> get.size is copy from the user space,  it can be set as 0x7fffffff,
> addition with sizeof(struct ipt_get_entries) can be overflow.

Patrick's point is that you're using "if (get.size >= INT_MAX /
sizeof(struct ipt_get_entries))"
So, did you find any chance that get.size * sizeof(struct
ipt_get_entries) >= INT_MAX ?

And, for the addition overflow, can it be caught by

"if (*len != sizeof(struct ipt_get_entries) + get.size)"  ???

>
>        if (*len != sizeof(struct ipt_get_entries) + get.size) {
>                duprintf("get_entries: %u != %zu\n",
>                         *len, sizeof(get) + get.size);
>                return -EINVAL;
>        }
>
> so, check get.size max value before addition with sizeof(struct
> ipt_get_entries) to prevent the integer overflow.
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