Commit f8a894b2 authored by Xin Long's avatar Xin Long Committed by David S. Miller

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: default avatarWei Chen <weichen@redhat.com>
Suggested-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarXin Long <lucien.xin@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a090bd4f
......@@ -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);
if (mod_delayed_work(addrconf_wq, &ifp->dad_work, delay))
in6_ifa_put(ifp);
}
static int snmp6_alloc_dev(struct inet6_dev *idev)
......
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