From: Xin Long Date: Thu, 15 Jun 2017 08:33:58 +0000 (+0800) Subject: ipv6: fix calling in6_ifa_hold incorrectly for dad work X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=f8a894b218138888542a5058d0e902378fd0d4ec;p=openwrt%2Fstaging%2Fblogic.git ipv6: fix calling in6_ifa_hold incorrectly for dad work Now when starting the dad work in addrconf_mod_dad_work, if the dad work is idle and queued, it needs to hold ifa. The problem is there's one gap in [1], during which if the pending dad work is removed elsewhere. It will miss to hold ifa, but the dad word is still idea and queue. if (!delayed_work_pending(&ifp->dad_work)) in6_ifa_hold(ifp); <--------------[1] mod_delayed_work(addrconf_wq, &ifp->dad_work, delay); An use-after-free issue can be caused by this. Chen Wei found this issue when WARN_ON(!hlist_unhashed(&ifp->addr_lst)) in net6_ifa_finish_destroy was hit because of it. As Hannes' suggestion, this patch is to fix it by holding ifa first in addrconf_mod_dad_work, then calling mod_delayed_work and putting ifa if the dad_work is already in queue. Note that this patch did not choose to fix it with: if (!mod_delayed_work(delay)) in6_ifa_hold(ifp); As with it, when delay == 0, dad_work would be scheduled immediately, all addrconf_mod_dad_work(0) callings had to be moved under ifp->lock. Reported-by: Wei Chen Suggested-by: Hannes Frederic Sowa Acked-by: Hannes Frederic Sowa Signed-off-by: Xin Long Signed-off-by: David S. Miller --- diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 6a4fb1e629fb..686c92375e81 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -332,9 +332,9 @@ static void addrconf_mod_rs_timer(struct inet6_dev *idev, static void addrconf_mod_dad_work(struct inet6_ifaddr *ifp, unsigned long delay) { - if (!delayed_work_pending(&ifp->dad_work)) - in6_ifa_hold(ifp); - mod_delayed_work(addrconf_wq, &ifp->dad_work, delay); + in6_ifa_hold(ifp); + if (mod_delayed_work(addrconf_wq, &ifp->dad_work, delay)) + in6_ifa_put(ifp); } static int snmp6_alloc_dev(struct inet6_dev *idev)