[PATCH 4.1 125/202] batman-adv: fix kernel crash due to missing NULL checks

[Greg Kroah-Hartman]

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

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

From: Marek Lindner <mareklindner@xxxxxxxxxxxxx>

commit 354136bcc3c4f40a2813bba8f57ca5267d812d15 upstream.

batadv_softif_vlan_get() may return NULL which has to be verified
by the caller.

Fixes: 35df3b298fc8 ("batman-adv: fix TT VLAN inconsistency on VLAN re-add")
Reported-by: Ryan Thompson <ryan@xxxxxxxx>
Signed-off-by: Marek Lindner <mareklindner@xxxxxxxxxxxxx>
Signed-off-by: Antonio Quartulli <antonio@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 net/batman-adv/soft-interface.c    |    3 +++
 net/batman-adv/translation-table.c |   18 ++++++++++++++----
 2 files changed, 17 insertions(+), 4 deletions(-)

--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -449,6 +449,9 @@ out:
  */
 void batadv_softif_vlan_free_ref(struct batadv_softif_vlan *vlan)
 {
+	if (!vlan)
+		return;
+
 	if (atomic_dec_and_test(&vlan->refcount)) {
 		spin_lock_bh(&vlan->bat_priv->softif_vlan_list_lock);
 		hlist_del_rcu(&vlan->list);
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -575,6 +575,9 @@ bool batadv_tt_local_add(struct net_devi
 
 	/* increase the refcounter of the related vlan */
 	vlan = batadv_softif_vlan_get(bat_priv, vid);
+	if (WARN(!vlan, "adding TT local entry %pM to non-existent VLAN %d",
+		 addr, BATADV_PRINT_VID(vid)))
+		goto out;
 
 	batadv_dbg(BATADV_DBG_TT, bat_priv,
 		   "Creating new local tt entry: %pM (vid: %d, ttvn: %d)\n",
@@ -1047,6 +1050,9 @@ uint16_t batadv_tt_local_remove(struct b
 
 	/* decrease the reference held for this vlan */
 	vlan = batadv_softif_vlan_get(bat_priv, vid);
+	if (!vlan)
+		goto out;
+
 	batadv_softif_vlan_free_ref(vlan);
 	batadv_softif_vlan_free_ref(vlan);
 
@@ -1147,8 +1153,10 @@ static void batadv_tt_local_table_free(s
 			/* decrease the reference held for this vlan */
 			vlan = batadv_softif_vlan_get(bat_priv,
 						      tt_common_entry->vid);
-			batadv_softif_vlan_free_ref(vlan);
-			batadv_softif_vlan_free_ref(vlan);
+			if (vlan) {
+				batadv_softif_vlan_free_ref(vlan);
+				batadv_softif_vlan_free_ref(vlan);
+			}
 
 			batadv_tt_local_entry_free_ref(tt_local);
 		}
@@ -3188,8 +3196,10 @@ static void batadv_tt_local_purge_pendin
 
 			/* decrease the reference held for this vlan */
 			vlan = batadv_softif_vlan_get(bat_priv, tt_common->vid);
-			batadv_softif_vlan_free_ref(vlan);
-			batadv_softif_vlan_free_ref(vlan);
+			if (vlan) {
+				batadv_softif_vlan_free_ref(vlan);
+				batadv_softif_vlan_free_ref(vlan);
+			}
 
 			batadv_tt_local_entry_free_ref(tt_local);
 		}


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