From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ding Tianhong 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 Message-ID: <520C241A.2030708@huawei.com> References: <520B48AE.8050103@huawei.com> <20130814101511.GC16264@order.stressinduktion.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit To: "David S. Miller" , Alexey Kuznetsov , James Morris , Hideaki YOSHIFUJI , Patrick McHardy , Jon Maloy , Eric Dumazet , Netdev Return-path: Received: from szxga03-in.huawei.com ([119.145.14.66]:21792 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758417Ab3HOAn5 (ORCPT ); Wed, 14 Aug 2013 20:43:57 -0400 In-Reply-To: <20130814101511.GC16264@order.stressinduktion.org> Sender: netdev-owner@vger.kernel.org List-ID: 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 >> Tested-by: Wang Weidong >> Cc: David S. Miller >> Cc: Sergei Shtylyov >> Cc: Eric Dumazet >> --- >> 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.:) > . >