From: Ding Tianhong <dingtianhong@huawei•com>
To: "David S. Miller" <davem@davemloft•net>,
Alexey Kuznetsov <kuznet@ms2•inr.ac.ru>,
James Morris <jmorris@namei•org>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6•org>,
Patrick McHardy <kaber@trash•net>,
Jon Maloy <jon.maloy@ericsson•com>,
Eric Dumazet <edumazet@google•com>,
Netdev <netdev@vger•kernel.org>
Subject: Re: [PATCH 1/3 v4] ipv6: do not disable temp_address when reaching max_address
Date: Thu, 15 Aug 2013 08:43:06 +0800 [thread overview]
Message-ID: <520C241A.2030708@huawei.com> (raw)
In-Reply-To: <20130814101511.GC16264@order.stressinduktion.org>
On 2013/8/14 18:15, Hannes Frederic Sowa wrote:
> On Wed, Aug 14, 2013 at 05:06:54PM +0800, Ding Tianhong wrote:
>> A LAN user can remotely disable temporary address which may lead
>> to privacy violatins and information disclosure.
>>
>> The reason is that the linux kernel uses the 'ipv6.max_addresses'
>> option to specify how many ipv6 addresses and interface may have.
>> The 'ipv6.regen_max_retry' (default value 3) option specifies
>> how many times the kernel will try to create a new address.
>>
>> But the kernel is not distinguish between the event of reaching
>> max_addresses for an interface and failing to generate a new address.
>> the kernel disable the temporary address after regenerate a new
>> address 'regen_max_retry' times.
>>
>> According RFC4941 3.3.7:
>>
>> ---------------------------------------
>>
>> If DAD indicates the address is already in use,
>> the node must generate a new randomized interface
>> identifier as described in section 3.2 above, and
>> repeat the previous steps as appropriate up to
>> TEMP_IDGEN_RETRIES times.
>>
>> If after TEMP_IDGEN_RETRIES consecutive attempts no
>> non-unique address was generated, the node must log
>> a system error and must not attempt to generate
>> temporary address for that interface.
>>
>> ------------------------------------------
>>
>> RFC4941 3.3.7 specifies that disabling the temp_address must happen
>> upon the address is already in use, not reach the max_address,
>> So we have to check the return err and distinguish the correct retry path.
>>
>> This fixes CVE-2013-0343
>
> I don't think this patch fixes CVE-2013-0343.
>
>>
>> Signed-off-by: Ding Tianhong <dingtianhong@huawei•com>
>> Tested-by: Wang Weidong <wangweidong1@huawei•com>
>> Cc: David S. Miller <davem@davemloft•net>
>> Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded•com>
>> Cc: Eric Dumazet <edumazet@google•com>
>> ---
>> net/ipv6/addrconf.c | 26 ++++++++++++++++++++++----
>> 1 file changed, 22 insertions(+), 4 deletions(-)
>>
>> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
>> index da4241c..7b55464 100644
>> --- a/net/ipv6/addrconf.c
>> +++ b/net/ipv6/addrconf.c
>> @@ -1134,10 +1134,28 @@ retry:
>> if (IS_ERR_OR_NULL(ift)) {
>> in6_ifa_put(ifp);
>> in6_dev_put(idev);
>> - pr_info("%s: retry temporary address regeneration\n", __func__);
>> - tmpaddr = &addr;
>> - write_lock(&idev->lock);
>> - goto retry;
>> +
>> + /* According RFC4941 3.3.7:
>> + * If DAD indicates the address is already in use,
>> + * the node must generate a new randomized interface
>> + * identifier as described in section 3.2 above, and
>> + * repeat the previous steps as appropriate up to
>> + * TEMP_IDGEN_RETRIES times.
>> + * If after TEMP_IDGEN_RETRIES consecutive attempts no
>> + * non-unique address was generated, the node must log
>> + * a system error and must not attempt to generate
>> + * temporary address for that interface.
>> + * So we have to check the return err and distinguish
>> + * the correct retry path.
>> + */
>> + if (PTR_ERR(ift) == -EEXIST) {
>
> -EEXIST is not the same as "ipv6 address is is already used on the
> subnet". I really don't see the point here. IMHO this breaks the intended
> regeneration logic.
>
> I fear a fix of CVE-2013-0343 will be a bit more complicated. ;) I give it a
> thought.
>
> Greetings,
>
> Hannes
>
>
ok, thanks for your feedback, I'll waiting you for more information to fix the problem.:)
> .
>
next prev parent reply other threads:[~2013-08-15 0:43 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-14 9:06 [PATCH 1/3 v4] ipv6: do not disable temp_address when reaching max_address Ding Tianhong
2013-08-14 10:15 ` Hannes Frederic Sowa
2013-08-15 0:43 ` Ding Tianhong [this message]
2013-08-15 1:24 ` Hannes Frederic Sowa
2013-08-15 2:16 ` Ding Tianhong
2013-08-15 17:36 ` Hannes Frederic Sowa
2013-08-15 19:07 ` Hannes Frederic Sowa
2013-08-16 0:48 ` Ding Tianhong
2013-08-16 11:07 ` Hannes Frederic Sowa
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