netfilter: nf_conntrack: flush net_gre->keymap_list only from gre helper

nf_ct_gre_keymap_flush() removes a nf_ct_gre_keymap object from
net_gre->keymap_list and frees the object. But it doesn't clean
a reference on this object from ct_pptp_info->keymap[dir].
Then nf_ct_gre_keymap_destroy() may release the same object again.

So nf_ct_gre_keymap_flush() can be called only when we are sure that
when nf_ct_gre_keymap_destroy will not be called.

nf_ct_gre_keymap is created by nf_ct_gre_keymap_add() and the right way
to destroy it is to call nf_ct_gre_keymap_destroy().

This patch marks nf_ct_gre_keymap_flush() as static, so this patch can
break compilation of third party modules, which use
nf_ct_gre_keymap_flush. I'm not sure this is the right way to deprecate
this function.

[  226.540793] general protection fault: 0000 [#1] SMP
[  226.541750] Modules linked in: nf_nat_pptp nf_nat_proto_gre
nf_conntrack_pptp nf_conntrack_proto_gre ip_gre ip_tunnel gre
ppp_deflate bsd_comp ppp_async crc_ccitt ppp_generic slhc xt_nat
iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat
nf_conntrack veth tun bridge stp llc ppdev microcode joydev pcspkr
serio_raw virtio_console virtio_balloon floppy parport_pc parport
pvpanic i2c_piix4 virtio_net drm_kms_helper ttm ata_generic virtio_pci
virtio_ring virtio drm i2c_core pata_acpi [last unloaded: ip_tunnel]
[  226.541776] CPU: 0 PID: 49 Comm: kworker/u4:2 Not tainted 3.14.0-rc8+ #101
[  226.541776] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  226.541776] Workqueue: netns cleanup_net
[  226.541776] task: ffff8800371e0000 ti: ffff88003730c000 task.ti: ffff88003730c000
[  226.541776] RIP: 0010:[<ffffffff81389ba9>]  [<ffffffff81389ba9>] __list_del_entry+0x29/0xd0
[  226.541776] RSP: 0018:ffff88003730dbd0  EFLAGS: 00010a83
[  226.541776] RAX: 6b6b6b6b6b6b6b6b RBX: ffff8800374e6c40 RCX: dead000000200200
[  226.541776] RDX: 6b6b6b6b6b6b6b6b RSI: ffff8800371e07d0 RDI: ffff8800374e6c40
[  226.541776] RBP: ffff88003730dbd0 R08: 0000000000000000 R09: 0000000000000000
[  226.541776] R10: 0000000000000001 R11: ffff88003730d92e R12: 0000000000000002
[  226.541776] R13: ffff88007a4c42d0 R14: ffff88007aef0000 R15: ffff880036cf0018
[  226.541776] FS:  0000000000000000(0000) GS:ffff88007fc00000(0000) knlGS:0000000000000000
[  226.541776] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[  226.541776] CR2: 00007f07f643f7d0 CR3: 0000000036fd2000 CR4: 00000000000006f0
[  226.541776] Stack:
[  226.541776]  ffff88003730dbe8 ffffffff81389c5d ffff8800374ffbe4 ffff88003730dc28
[  226.541776]  ffffffffa0162a43 ffffffffa01627c5 ffff88007a4c42d0 ffff88007aef0000
[  226.541776]  ffffffffa01651c0 ffff88007a4c45e0 ffff88007aef0000 ffff88003730dc40
[  226.541776] Call Trace:
[  226.541776]  [<ffffffff81389c5d>] list_del+0xd/0x30
[  226.541776]  [<ffffffffa0162a43>] nf_ct_gre_keymap_destroy+0x283/0x2d0 [nf_conntrack_proto_gre]
[  226.541776]  [<ffffffffa01627c5>] ? nf_ct_gre_keymap_destroy+0x5/0x2d0 [nf_conntrack_proto_gre]
[  226.541776]  [<ffffffffa0162ab7>] gre_destroy+0x27/0x70 [nf_conntrack_proto_gre]
[  226.541776]  [<ffffffffa0117de3>] destroy_conntrack+0x83/0x200 [nf_conntrack]
[  226.541776]  [<ffffffffa0117d87>] ? destroy_conntrack+0x27/0x200 [nf_conntrack]
[  226.541776]  [<ffffffffa0117d60>] ? nf_conntrack_hash_check_insert+0x2e0/0x2e0 [nf_conntrack]
[  226.541776]  [<ffffffff81630142>] nf_conntrack_destroy+0x72/0x180
[  226.541776]  [<ffffffff816300d5>] ? nf_conntrack_destroy+0x5/0x180
[  226.541776]  [<ffffffffa011ef80>] ? kill_l3proto+0x20/0x20 [nf_conntrack]
[  226.541776]  [<ffffffffa011847e>] nf_ct_iterate_cleanup+0x14e/0x170 [nf_conntrack]
[  226.541776]  [<ffffffffa011f74b>] nf_ct_l4proto_pernet_unregister+0x5b/0x90 [nf_conntrack]
[  226.541776]  [<ffffffffa0162409>] proto_gre_net_exit+0x19/0x30 [nf_conntrack_proto_gre]
[  226.541776]  [<ffffffff815edf89>] ops_exit_list.isra.1+0x39/0x60
[  226.541776]  [<ffffffff815eecc0>] cleanup_net+0x100/0x1d0
[  226.541776]  [<ffffffff810a608a>] process_one_work+0x1ea/0x4f0
[  226.541776]  [<ffffffff810a6028>] ? process_one_work+0x188/0x4f0
[  226.541776]  [<ffffffff810a64ab>] worker_thread+0x11b/0x3a0
[  226.541776]  [<ffffffff810a6390>] ? process_one_work+0x4f0/0x4f0
[  226.541776]  [<ffffffff810af42d>] kthread+0xed/0x110
[  226.541776]  [<ffffffff8173d4dc>] ? _raw_spin_unlock_irq+0x2c/0x40
[  226.541776]  [<ffffffff810af340>] ? kthread_create_on_node+0x200/0x200
[  226.541776]  [<ffffffff8174747c>] ret_from_fork+0x7c/0xb0
[  226.541776]  [<ffffffff810af340>] ? kthread_create_on_node+0x200/0x200
[  226.541776] Code: 00 00 55 48 8b 17 48 b9 00 01 10 00 00 00 ad de
48 8b 47 08 48 89 e5 48 39 ca 74 29 48 b9 00 02 20 00 00 00 ad de 48
39 c8 74 7a <4c> 8b 00 4c 39 c7 75 53 4c 8b 42 08 4c 39 c7 75 2b 48 89
42 08
[  226.541776] RIP  [<ffffffff81389ba9>] __list_del_entry+0x29/0xd0
[  226.541776]  RSP <ffff88003730dbd0>
[  226.612193] ---[ end trace 985ae23ddfcc357c ]---

Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/linux/netfilter/nf_conntrack_proto_gre.h

@@ -87,7 +87,6 @@ int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
 /* delete keymap entries */
 void nf_ct_gre_keymap_destroy(struct nf_conn *ct);
 
-void nf_ct_gre_keymap_flush(struct net *net);
 void nf_nat_need_gre(void);
 
 #endif /* __KERNEL__ */

net/netfilter/nf_conntrack_pptp.c

@@ -605,32 +605,14 @@ static struct nf_conntrack_helper pptp __read_mostly = {
 	.expect_policy		= &pptp_exp_policy,
 };
 
-static void nf_conntrack_pptp_net_exit(struct net *net)
-{
-	nf_ct_gre_keymap_flush(net);
-}
-
-static struct pernet_operations nf_conntrack_pptp_net_ops = {
-	.exit = nf_conntrack_pptp_net_exit,
-};
-
 static int __init nf_conntrack_pptp_init(void)
 {
-	int rv;
-
-	rv = nf_conntrack_helper_register(&pptp);
-	if (rv < 0)
-		return rv;
-	rv = register_pernet_subsys(&nf_conntrack_pptp_net_ops);
-	if (rv < 0)
-		nf_conntrack_helper_unregister(&pptp);
-	return rv;
+	return nf_conntrack_helper_register(&pptp);
 }
 
 static void __exit nf_conntrack_pptp_fini(void)
 {
 	nf_conntrack_helper_unregister(&pptp);
-	unregister_pernet_subsys(&nf_conntrack_pptp_net_ops);
 }
 
 module_init(nf_conntrack_pptp_init);

net/netfilter/nf_conntrack_proto_gre.c

@@ -66,7 +66,7 @@ static inline struct netns_proto_gre *gre_pernet(struct net *net)
 	return net_generic(net, proto_gre_net_id);
 }
 
-void nf_ct_gre_keymap_flush(struct net *net)
+static void nf_ct_gre_keymap_flush(struct net *net)
 {
 	struct netns_proto_gre *net_gre = gre_pernet(net);
 	struct nf_ct_gre_keymap *km, *tmp;
@@ -78,7 +78,6 @@ void nf_ct_gre_keymap_flush(struct net *net)
 	}
 	write_unlock_bh(&net_gre->keymap_lock);
 }
-EXPORT_SYMBOL(nf_ct_gre_keymap_flush);
 
 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
 				const struct nf_conntrack_tuple *t)