batman-adv: Avoid nullptr dereference in dat after vlan_insert_tag

vlan_insert_tag can return NULL on errors. The distributed arp table code
therefore has to check the return value of vlan_insert_tag for NULL before
it can safely operate on this pointer.

Fixes: be1db4f6615b ("batman-adv: make the Distributed ARP Table vlan aware")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c
index 278800a..aee3b39 100644 (file)
--- a/net/batman-adv/distributed-arp-table.c
+++ b/net/batman-adv/distributed-arp-table.c
@@ -1009,9 +1009,12 @@ bool batadv_dat_snoop_outgoing_arp_request(struct batadv_priv *bat_priv,
                if (!skb_new)
                        goto out;
 
-               if (vid & BATADV_VLAN_HAS_TAG)
+               if (vid & BATADV_VLAN_HAS_TAG) {
                        skb_new = vlan_insert_tag(skb_new, htons(ETH_P_8021Q),
                                                  vid & VLAN_VID_MASK);
+                       if (!skb_new)
+                               goto out;
+               }
 
                skb_reset_mac_header(skb_new);
                skb_new->protocol = eth_type_trans(skb_new,
@@ -1089,9 +1092,12 @@ bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv,
         */
        skb_reset_mac_header(skb_new);
 
-       if (vid & BATADV_VLAN_HAS_TAG)
+       if (vid & BATADV_VLAN_HAS_TAG) {
                skb_new = vlan_insert_tag(skb_new, htons(ETH_P_8021Q),
                                          vid & VLAN_VID_MASK);
+               if (!skb_new)
+                       goto out;
+       }
 
        /* To preserve backwards compatibility, the node has choose the outgoing
         * format based on the incoming request packet type. The assumption is