diff mbox series

[06/11] batman-adv: Prevent duplicated softif_vlan entry

Message ID	20180919122213.23108-7-sw@simonwunderlich.de (mailing list archive)
State	Not Applicable, archived
Delegated to:	Simon Wunderlich
Headers	Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=79.140.42.25; helo=mail.mail.packetmixer.de; envelope-from=sw@simonwunderlich.de; receiver=<UNKNOWN> From: Simon Wunderlich <sw@simonwunderlich.de> To: davem@davemloft.net Date: Wed, 19 Sep 2018 14:22:08 +0200 Message-Id: <20180919122213.23108-7-sw@simonwunderlich.de> In-Reply-To: <20180919122213.23108-1-sw@simonwunderlich.de> References: <20180919122213.23108-1-sw@simonwunderlich.de> Subject: [B.A.T.M.A.N.] [PATCH 06/11] batman-adv: Prevent duplicated softif_vlan entry Precedence: list Reply-To: The list for a Better Approach To Mobile Ad-hoc Networking <b.a.t.m.a.n@lists.open-mesh.org> Cc: netdev@vger.kernel.org, b.a.t.m.a.n@lists.open-mesh.org Errors-To: b.a.t.m.a.n-bounces@lists.open-mesh.org Sender: "B.A.T.M.A.N" <b.a.t.m.a.n-bounces@lists.open-mesh.org>
Series	[01/11] batman-adv: Avoid probe ELP information leak \| [01/11] batman-adv: Avoid probe ELP information leak [02/11] batman-adv: Fix segfault when writing to throughput_override [03/11] batman-adv: Fix segfault when writing to sysfs elp_interval [04/11] batman-adv: Prevent duplicated gateway_node entry [05/11] batman-adv: Prevent duplicated nc_node entry [06/11] batman-adv: Prevent duplicated softif_vlan entry [07/11] batman-adv: Prevent duplicated global TT entry [08/11] batman-adv: Prevent duplicated tvlv handler [09/11] batman-adv: fix backbone_gw refcount on queue_work() failure [10/11] batman-adv: fix hardif_neigh refcount on queue_work() failure [11/11] batman-adv: Increase version number to 2018.3

Commit Message

Simon Wunderlich Sept. 19, 2018, 12:22 p.m. UTC

  From: Sven Eckelmann <sven@narfation.org>

The function batadv_softif_vlan_get is responsible for adding new
softif_vlan to the softif_vlan_list. It first checks whether the entry
already is in the list or not. If it is, then the creation of a new entry
is aborted.

But the lock for the list is only held when the list is really modified.
This could lead to duplicated entries because another context could create
an entry with the same key between the check and the list manipulation.

The check and the manipulation of the list must therefore be in the same
locked code section.

Fixes: 5d2c05b21337 ("batman-adv: add per VLAN interface attribute framework")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
---
 net/batman-adv/soft-interface.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff mbox series

Patch

diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 1485263a348b..626ddca332db 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -574,15 +574,20 @@  int batadv_softif_create_vlan(struct batadv_priv *bat_priv, unsigned short vid)
 	struct batadv_softif_vlan *vlan;
 	int err;
 
+	spin_lock_bh(&bat_priv->softif_vlan_list_lock);
+
 	vlan = batadv_softif_vlan_get(bat_priv, vid);
 	if (vlan) {
 		batadv_softif_vlan_put(vlan);
+		spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
 		return -EEXIST;
 	}
 
 	vlan = kzalloc(sizeof(*vlan), GFP_ATOMIC);
-	if (!vlan)
+	if (!vlan) {
+		spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
 		return -ENOMEM;
+	}
 
 	vlan->bat_priv = bat_priv;
 	vlan->vid = vid;
@@ -590,17 +595,23 @@  int batadv_softif_create_vlan(struct batadv_priv *bat_priv, unsigned short vid)
 
 	atomic_set(&vlan->ap_isolation, 0);
 
+	kref_get(&vlan->refcount);
+	hlist_add_head_rcu(&vlan->list, &bat_priv->softif_vlan_list);
+	spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
+
+	/* batadv_sysfs_add_vlan cannot be in the spinlock section due to the
+	 * sleeping behavior of the sysfs functions and the fs_reclaim lock
+	 */
 	err = batadv_sysfs_add_vlan(bat_priv->soft_iface, vlan);
 	if (err) {
-		kfree(vlan);
+		/* ref for the function */
+		batadv_softif_vlan_put(vlan);
+
+		/* ref for the list */
+		batadv_softif_vlan_put(vlan);
 		return err;
 	}
 
-	spin_lock_bh(&bat_priv->softif_vlan_list_lock);
-	kref_get(&vlan->refcount);
-	hlist_add_head_rcu(&vlan->list, &bat_priv->softif_vlan_list);
-	spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
-
 	/* add a new TT local entry. This one will be marked with the NOPURGE
 	 * flag
 	 */