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[PATCH 4.1 02/46] l2tp: protect tunnel->del_work by ref_count

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4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alexander Couzens <lynxis@fe80.eu>

[ Upstream commit 06a15f51cf3618e32a73871ee6a547ef7fd902b5 ]

There is a small chance that tunnel_free() is called before tunnel->del_work scheduled
resulting in a zero pointer dereference.

Signed-off-by: Alexander Couzens <lynxis@fe80.eu>
Acked-by: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/l2tp/l2tp_core.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1319,7 +1319,7 @@ static void l2tp_tunnel_del_work(struct
 	tunnel = container_of(work, struct l2tp_tunnel, del_work);
 	sk = l2tp_tunnel_sock_lookup(tunnel);
 	if (!sk)
-		return;
+		goto out;
 
 	sock = sk->sk_socket;
 
@@ -1340,6 +1340,8 @@ static void l2tp_tunnel_del_work(struct
 	}
 
 	l2tp_tunnel_sock_put(sk);
+out:
+	l2tp_tunnel_dec_refcount(tunnel);
 }
 
 /* Create a socket for the tunnel, if one isn't set up by
@@ -1639,8 +1641,13 @@ EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
  */
 int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
 {
+	l2tp_tunnel_inc_refcount(tunnel);
 	l2tp_tunnel_closeall(tunnel);
-	return (false == queue_work(l2tp_wq, &tunnel->del_work));
+	if (false == queue_work(l2tp_wq, &tunnel->del_work)) {
+		l2tp_tunnel_dec_refcount(tunnel);
+		return 1;
+	}
+	return 0;
 }
 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
 


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[PATCH 4.1 00/46] 4.1.12-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 05/46] inet: fix races in reqsk_queue_hash_req() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 06/46] net: add pfmemalloc check in sk_add_backlog() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 04/46] skbuff: Fix skb checksum partial check. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 02/46] l2tp: protect tunnel->del_work by ref_count Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 16/46] af_unix: return data from multiple SKBs on recv() with MSG_PEEK flag Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 30/46] i2c: designware-platdrv: enable RuntimePM before registering to the core Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 29/46] i2c: designware: Do not use parameters from ACPI on Dell Inspiron 7348 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 34/46] drm/radeon: attach tile property to mst connector Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 17/46] net/unix: fix logic about sk_peek_offset Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 32/46] drm/nouveau/fbcon: take runpm reference when userspace has an open fd Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 09/46] bpf: fix panic in SO_GET_FILTER with native ebpf programs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 27/46] i2c: rcar: enable RuntimePM before registering to the core Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 31/46] workqueue: make sure delayed work run in local cpu Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 39/46] sched/preempt: Fix cond_resched_lock() and cond_resched_softirq() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
    Re: [PATCH 4.1 39/46] sched/preempt: Fix cond_resched_lock() and  cond_resched_softirq() Thomas Backlund <backlund.thomas@gmail.com> - 2015-10-23 22:20 +0200
      Re: [PATCH 4.1 39/46] sched/preempt: Fix cond_resched_lock() and  cond_resched_softirq() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-24 01:30 +0200
  Re: [PATCH 4.1 00/46] 4.1.12-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2015-10-23 22:40 +0200
    Re: [PATCH 4.1 00/46] 4.1.12-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-24 01:30 +0200
      Re: [PATCH 4.1 00/46] 4.1.12-stable review Guenter Roeck <linux@roeck-us.net> - 2015-10-24 03:20 +0200
  Re: [PATCH 4.1 00/46] 4.1.12-stable review Guenter Roeck <linux@roeck-us.net> - 2015-10-24 05:20 +0200
    Re: [PATCH 4.1 00/46] 4.1.12-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-24 15:30 +0200

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