Re: [PATCH] Netfilter: Fix integer overflow in net/ipv6/netfilter/ip6_tables.c

[Xiaotian Feng]

On Tue, Mar 23, 2010 at 10:37 AM, wzt wzt <wzt.wzt@xxxxxxxxx> wrote:
>> 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 ?
>>
> would you carefully read my explain???
> get.size is copy from the user space, Âit can be set as 0x7fffffff,
> addition with sizeof(struct ipt_get_entries) can be overflow.
>

get.size is unsigned int, UINT_MAX is 0x FFFFFFFF, not 0x7FFFFFFF
And you're metioning "addition", then why you're checking as "multiplication"?

>> And, for the addition overflow, can it be caught by
>>
>> "if (*len != sizeof(struct ipt_get_entries) + get.size)" Â???
>>
> sizeof(struct ipt_get_entries) + get.size can be overflow as *len,
> get.size is control by user space with copy_from_user().


>
> On Tue, Mar 23, 2010 at 10:29 AM, Xiaotian Feng <xtfeng@xxxxxxxxx> wrote:
>> On Tue, Mar 23, 2010 at 9:34 AM, wzt wzt <wzt.wzt@xxxxxxxxx> 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, Âit 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)" Â???
>>
>>>
>>> Â Â Â Âif (*len != sizeof(struct ipt_get_entries) + get.size) {
>>> Â Â Â Â Â Â Â Âduprintf("get_entries: %u != %zu\n",
>>> Â Â Â Â Â Â Â Â Â Â Â Â *len, sizeof(get) + get.size);
>>> Â Â Â Â Â Â Â Âreturn -EINVAL;
>>> Â Â Â Â}
>>>
>>> so, check get.size max value before addition with sizeof(struct
>>> ipt_get_entries) to prevent the integer overflow.
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>>
>
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