diff options
authorHannes Frederic Sowa <hannes@stressinduktion.org>2013-08-16 13:02:27 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-09-14 06:54:55 -0700
commitad558a2970f60e8a52f048c96f0f6ea7dc691fb7 (patch)
parentb59bde78dbf049a2671603034562940ac6eb1181 (diff)
ipv6: remove max_addresses check from ipv6_create_tempaddr
[ Upstream commit 4b08a8f1bd8cb4541c93ec170027b4d0782dab52 ] Because of the max_addresses check attackers were able to disable privacy extensions on an interface by creating enough autoconfigured addresses: <http://seclists.org/oss-sec/2012/q4/292> But the check is not actually needed: max_addresses protects the kernel to install too many ipv6 addresses on an interface and guards addrconf_prefix_rcv to install further addresses as soon as this limit is reached. We only generate temporary addresses in direct response of a new address showing up. As soon as we filled up the maximum number of addresses of an interface, we stop installing more addresses and thus also stop generating more temp addresses. Even if the attacker tries to generate a lot of temporary addresses by announcing a prefix and removing it again (lifetime == 0) we won't install more temp addresses, because the temporary addresses do count to the maximum number of addresses, thus we would stop installing new autoconfigured addresses when the limit is reached. This patch fixes CVE-2013-0343 (but other layer-2 attacks are still possible). Thanks to Ding Tianhong to bring this topic up again. Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Cc: Ding Tianhong <dingtianhong@huawei.com> Cc: George Kargiotakis <kargig@void.gr> Cc: P J P <ppandit@redhat.com> Cc: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org> Acked-by: Ding Tianhong <dingtianhong@huawei.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 4 insertions, 6 deletions
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index fb8c94c4ab8..d3057f9b04a 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1124,12 +1124,10 @@ retry:
if (ifp->flags & IFA_F_OPTIMISTIC)
addr_flags |= IFA_F_OPTIMISTIC;
- ift = !max_addresses ||
- ipv6_count_addresses(idev) < max_addresses ?
- ipv6_add_addr(idev, &addr, tmp_plen,
- ipv6_addr_type(&addr)&IPV6_ADDR_SCOPE_MASK,
- addr_flags) : NULL;
- if (IS_ERR_OR_NULL(ift)) {
+ ift = ipv6_add_addr(idev, &addr, tmp_plen,
+ ipv6_addr_type(&addr)&IPV6_ADDR_SCOPE_MASK,
+ addr_flags);
+ if (IS_ERR(ift)) {
pr_info("%s: retry temporary address regeneration\n", __func__);