[PATCH 4.20 21/80] ip6mr: Fix notifiers call on mroute_clean_tables()

Greg Kroah-Hartman
2019-02-04T10:51:09Z

From: Nir Dotan <nird@mellanox.com>

[ Upstream commit 146820cc240f4389cf33481c058d9493aef95e25 ]

When the MC route socket is closed, mroute_clean_tables() is called to
cleanup existing routes. Mistakenly notifiers call was put on the cleanup
of the unresolved MC route entries cache.
In a case where the MC socket closes before an unresolved route expires,
the notifier call leads to a crash, caused by the driver trying to
increment a non initialized refcount_t object [1] and then when handling
is done, to decrement it [2]. This was detected by a test recently added in
commit 6d4efada3b82 ("selftests: forwarding: Add multicast routing test").

Fix that by putting notifiers call on the resolved entries traversal,
instead of on the unresolved entries traversal.

[1]

[ 245.748967] refcount_t: increment on 0; use-after-free.
[ 245.754829] WARNING: CPU: 3 PID: 3223 at lib/refcount.c:153 refcount_inc_checked+0x2b/0x30
...
[ 245.802357] Hardware name: Mellanox Technologies Ltd. MSN2740/SA001237, BIOS 5.6.5 06/07/2016
[ 245.811873] RIP: 0010:refcount_inc_checked+0x2b/0x30
...
[ 245.907487] Call Trace:
[ 245.910231] mlxsw_sp_router_fib_event.cold.181+0x42/0x47 [mlxsw_spectrum]
[ 245.917913] notifier_call_chain+0x45/0x7
[ 245.922484] atomic_notifier_call_chain+0x15/0x20
[ 245.927729] call_fib_notifiers+0x15/0x30
[ 245.932205] mroute_clean_tables+0x372/0x3f
[ 245.936971] ip6mr_sk_done+0xb1/0xc0
[ 245.940960] ip6_mroute_setsockopt+0x1da/0x5f0
...

[2]

[ 246.128487] refcount_t: underflow; use-after-free.
[ 246.133859] WARNING: CPU: 0 PID: 7 at lib/refcount.c:187 refcount_sub_and_test_checked+0x4c/0x60
[ 246.183521] Hardware name: Mellanox Technologies Ltd. MSN2740/SA001237, BIOS 5.6.5 06/07/2016
...
[ 246.193062] Workqueue: mlxsw_core_ordered mlxsw_sp_router_fibmr_event_work [mlxsw_spectrum]
[ 246.202394] RIP: 0010:refcount_sub_and_test_checked+0x4c/0x60
...
[ 246.298889] Call Trace:
[ 246.301617] refcount_dec_and_test_checked+0x11/0x20
[ 246.307170] mlxsw_sp_router_fibmr_event_work.cold.196+0x47/0x78 [mlxsw_spectrum]
[ 246.315531] process_one_work+0x1fa/0x3f0
[ 246.320005] worker_thread+0x2f/0x3e0
[ 246.324083] kthread+0x118/0x130
[ 246.327683] ? wq_update_unbound_numa+0x1b0/0x1b0
[ 246.332926] ? kthread_park+0x80/0x80
[ 246.337013] ret_from_fork+0x1f/0x30

Fixes: 088aa3eec2ce ("ip6mr: Support fib notifications")
Signed-off-by: Nir Dotan <nird@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv6/ip6mr.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -1516,6 +1516,9 @@ static void mroute_clean_tables(struct m
continue;
rhltable_remove(&mrt->mfc_hash, &c->mnode, ip6mr_rht_params);
list_del_rcu(&c->list);
+ call_ip6mr_mfc_entry_notifiers(read_pnet(&mrt->net),
+ FIB_EVENT_ENTRY_DEL,
+ (struct mfc6_cache *)c, mrt->id);
mr6_netlink_event(mrt, (struct mfc6_cache *)c, RTM_DELROUTE);
mr_cache_put(c);
}
@@ -1524,10 +1527,6 @@ static void mroute_clean_tables(struct m
spin_lock_bh(&mfc_unres_lock);
list_for_each_entry_safe(c, tmp, &mrt->mfc_unres_queue, list) {
list_del(&c->list);
- call_ip6mr_mfc_entry_notifiers(read_pnet(&mrt->net),
- FIB_EVENT_ENTRY_DEL,
- (struct mfc6_cache *)c,
- mrt->id);
mr6_netlink_event(mrt, (struct mfc6_cache *)c,
RTM_DELROUTE);
ip6mr_destroy_unres(mrt, (struct mfc6_cache *)c);