netdev - [PATCH net-next 2/3] inet: frags: call inet_frags_fini() after unregister_pernet

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Message-Id: <20190527235649.45274-3-edumazet@google.com>
Date:   Mon, 27 May 2019 16:56:48 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 2/3] inet: frags: call inet_frags_fini() after unregister_pernet_subsys()

Both IPv6 and 6lowpan are calling inet_frags_fini() too soon.

inet_frags_fini() is dismantling a kmem_cache, that might be needed
later when unregister_pernet_subsys() eventually has to remove
frags queues from hash tables and free them.

This fixes potential use-after-free, and is a prereq for the following patch.

Fixes: d4ad4d22e7ac ("inet: frags: use kmem_cache for inet_frag_queue")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ieee802154/6lowpan/reassembly.c | 2 +-
 net/ipv6/reassembly.c               | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ieee802154/6lowpan/reassembly.c b/net/ieee802154/6lowpan/reassembly.c
index e59c3b7089691ef95ce3b7ce02afe68ffc256dcc..5b56f16ed86b09ac7235ebaf741cc8c434bbef5c 100644
--- a/net/ieee802154/6lowpan/reassembly.c
+++ b/net/ieee802154/6lowpan/reassembly.c
@@ -540,7 +540,7 @@ int __init lowpan_net_frag_init(void)
 
 void lowpan_net_frag_exit(void)
 {
-	inet_frags_fini(&lowpan_frags);
 	lowpan_frags_sysctl_unregister();
 	unregister_pernet_subsys(&lowpan_frags_ops);
+	inet_frags_fini(&lowpan_frags);
 }
diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
index 836ea964cf140d8b0134894455f18addc069e13e..ff5b6d8de2c6e65f5b2925649c77fad900b1e768 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -583,8 +583,8 @@ int __init ipv6_frag_init(void)
 
 void ipv6_frag_exit(void)
 {
-	inet_frags_fini(&ip6_frags);
 	ip6_frags_sysctl_unregister();
 	unregister_pernet_subsys(&ip6_frags_ops);
 	inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
+	inet_frags_fini(&ip6_frags);
 }
-- 
2.22.0.rc1.257.g3120a18244-goog