diff options
authorHannes Frederic Sowa <hannes@stressinduktion.org>2013-10-24 07:48:24 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-11-20 12:27:46 -0800
commit8ffff756458db53555ca36a97766f1731f6719cc (patch)
parentb9099fea22395af057dec42c678f47cf746cc998 (diff)
ipv6: ip6_dst_check needs to check for expired dst_entries
[ Upstream commit e3bc10bd95d7fcc3f2ac690c6ff22833ea6781d6 ] On receiving a packet too big icmp error we check if our current cached dst_entry in the socket is still valid. This validation check did not care about the expiration of the (cached) route. The error path I traced down: The socket receives a packet too big mtu notification. It still has a valid dst_entry and thus issues the ip6_rt_pmtu_update on this dst_entry, setting RTF_EXPIRE and updates the dst.expiration value (which could fail because of not up-to-date expiration values, see previous patch). In some seldom cases we race with a) the ip6_fib gc or b) another routing lookup which would result in a recreation of the cached rt6_info from its parent non-cached rt6_info. While copying the rt6_info we reinitialize the metrics store by copying it over from the parent thus invalidating the just installed pmtu update (both dsts use the same key to the inetpeer storage). The dst_entry with the just invalidated metrics data would just get its RTF_EXPIRES flag cleared and would continue to stay valid for the socket. We should have not issued the pmtu update on the already expired dst_entry in the first placed. By checking the expiration on the dst entry and doing a relookup in case it is out of date we close the race because we would install a new rt6_info into the fib before we issue the pmtu update, thus closing this race. Not reliably updating the dst.expire value was fixed by the patch "ipv6: reset dst.expires value when clearing expire flag". Reported-by: Steinar H. Gunderson <sgunderson@bigfoot.com> Reported-by: Valentijn Sessink <valentyn@blub.net> Cc: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Reviewed-by: Eric Dumazet <edumazet@google.com> Tested-by: Valentijn Sessink <valentyn@blub.net> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 6 insertions, 3 deletions
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 3c1f493ccc6..548a1f7c1a2 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1084,10 +1084,13 @@ static struct dst_entry *ip6_dst_check(struct dst_entry *dst, u32 cookie)
if (rt->rt6i_genid != rt_genid(dev_net(rt->dst.dev)))
return NULL;
- if (rt->rt6i_node && (rt->rt6i_node->fn_sernum == cookie))
- return dst;
+ if (!rt->rt6i_node || (rt->rt6i_node->fn_sernum != cookie))
+ return NULL;
- return NULL;
+ if (rt6_check_expired(rt))
+ return NULL;
+ return dst;
static struct dst_entry *ip6_negative_advice(struct dst_entry *dst)