[PATCH 5.18 57/88] net: mld: fix reference count leak in mld_{query | report}_work()

Greg Kroah-Hartman
2022-08-01T12:16:22Z

From: Taehee Yoo <ap420073@gmail.com>

[ Upstream commit 3e7d18b9dca388940a19cae30bfc1f76dccd8c28 ]

mld_{query | report}_work() processes queued events.
If there are too many events in the queue, it re-queue a work.
And then, it returns without in6_dev_put().
But if queuing is failed, it should call in6_dev_put(), but it doesn't.
So, a reference count leak would occur.

THREAD0 THREAD1
mld_report_work()
spin_lock_bh()
if (!mod_delayed_work())
in6_dev_hold();
spin_unlock_bh()
spin_lock_bh()
schedule_delayed_work()
spin_unlock_bh()

Script to reproduce(by Hangbin Liu):
ip netns add ns1
ip netns add ns2
ip netns exec ns1 sysctl -w net.ipv6.conf.all.force_mld_version=1
ip netns exec ns2 sysctl -w net.ipv6.conf.all.force_mld_version=1

ip -n ns1 link add veth0 type veth peer name veth0 netns ns2
ip -n ns1 link set veth0 up
ip -n ns2 link set veth0 up

for i in `seq 50`; do
for j in `seq 100`; do
ip -n ns1 addr add 2021:${i}::${j}/64 dev veth0
ip -n ns2 addr add 2022:${i}::${j}/64 dev veth0
done
done
modprobe -r veth
ip -a netns del

splat looks like:
unregister_netdevice: waiting for veth0 to become free. Usage count = 2
leaked reference.
ipv6_add_dev+0x324/0xec0
addrconf_notify+0x481/0xd10
raw_notifier_call_chain+0xe3/0x120
call_netdevice_notifiers+0x106/0x160
register_netdevice+0x114c/0x16b0
veth_newlink+0x48b/0xa50 [veth]
rtnl_newlink+0x11a2/0x1a40
rtnetlink_rcv_msg+0x63f/0xc00
netlink_rcv_skb+0x1df/0x3e0
netlink_unicast+0x5de/0x850
netlink_sendmsg+0x6c9/0xa90
____sys_sendmsg+0x76a/0x780
__sys_sendmsg+0x27c/0x340
do_syscall_64+0x43/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Tested-by: Hangbin Liu <liuhangbin@gmail.com>
Fixes: f185de28d9ae ("mld: add new workqueues for process mld events")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv6/mcast.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 7f695c39d9a8..87c699d57b36 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1522,7 +1522,6 @@ static void mld_query_work(struct work_struct *work)

if (++cnt >= MLD_MAX_QUEUE) {
rework = true;
- schedule_delayed_work(&idev->mc_query_work, 0);
break;
}
}
@@ -1533,8 +1532,10 @@ static void mld_query_work(struct work_struct *work)
__mld_query_work(skb);
mutex_unlock(&idev->mc_lock);

- if (!rework)
- in6_dev_put(idev);
+ if (rework && queue_delayed_work(mld_wq, &idev->mc_query_work, 0))
+ return;
+
+ in6_dev_put(idev);
}

/* called with rcu_read_lock() */
@@ -1624,7 +1625,6 @@ static void mld_report_work(struct work_struct *work)

if (++cnt >= MLD_MAX_QUEUE) {
rework = true;
- schedule_delayed_work(&idev->mc_report_work, 0);
break;
}
}
@@ -1635,8 +1635,10 @@ static void mld_report_work(struct work_struct *work)
__mld_report_work(skb);
mutex_unlock(&idev->mc_lock);

- if (!rework)
- in6_dev_put(idev);
+ if (rework && queue_delayed_work(mld_wq, &idev->mc_report_work, 0))
+ return;
+
+ in6_dev_put(idev);
}

static bool is_in(struct ifmcaddr6 *pmc, struct ip6_sf_list *psf, int type,
--
2.35.1