batman-adv: Avoid nullptr dereference in bla after vlan_insert_tag

commit 10c78f5854d361ded4736c1831948e0a5f67b932 upstream.

vlan_insert_tag can return NULL on errors. The bridge loop avoidance code
therefore has to check the return value of vlan_insert_tag for NULL before
it can safely operate on this pointer.

Fixes: 23721387c409 ("batman-adv: add basic bridge loop avoidance code")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c
index 90673ff8b87bfbcd149afe1d0306d3218f6bfbbe..932628c0d7a1b67d24e18b871df06ce72f9d2add 100644 (file)
--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -338,9 +338,12 @@ static void batadv_bla_send_claim(struct batadv_priv *bat_priv, uint8_t *mac,
                break;
        }
 
-       if (vid & BATADV_VLAN_HAS_TAG)
+       if (vid & BATADV_VLAN_HAS_TAG) {
                skb = vlan_insert_tag(skb, htons(ETH_P_8021Q),
                                      vid & VLAN_VID_MASK);
+               if (!skb)
+                       goto out;
+       }
 
        skb_reset_mac_header(skb);
        skb->protocol = eth_type_trans(skb, soft_iface);