| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.11 23/84] ipv6: fix calling in6_ifa_hold incorrectly for dad work | Date | Mon, 3 Jul 2017 15:35:03 +0200 |
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4.11-stable review patch. If anyone has any objections, please let me know.
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From: Xin Long <lucien.xin@gmail.com>
[ Upstream commit f8a894b218138888542a5058d0e902378fd0d4ec ]
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 <weichen@redhat.com> Suggested-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: Xin Long <lucien.xin@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- net/ipv6/addrconf.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -328,9 +328,9 @@ static void addrconf_mod_rs_timer(struct 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)
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