batman-adv: check return value of pskb_trim_rcsum()

Reported-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Acked-by: Martin Hundebøll <martin@hundeboll.net>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>

net/batman-adv/network-coding.c

@@ -1514,6 +1514,7 @@ batadv_nc_skb_decode_packet(struct batadv_priv *bat_priv, struct sk_buff *skb,
 	struct ethhdr *ethhdr, ethhdr_tmp;
 	uint8_t *orig_dest, ttl, ttvn;
 	unsigned int coding_len;
+	int err;
 
 	/* Save headers temporarily */
 	memcpy(&coded_packet_tmp, skb->data, sizeof(coded_packet_tmp));
@@ -1568,8 +1569,11 @@ batadv_nc_skb_decode_packet(struct batadv_priv *bat_priv, struct sk_buff *skb,
 			 coding_len);
 
 	/* Resize decoded skb if decoded with larger packet */
-	if (nc_packet->skb->len > coding_len + h_size)
-		pskb_trim_rcsum(skb, coding_len + h_size);
+	if (nc_packet->skb->len > coding_len + h_size) {
+		err = pskb_trim_rcsum(skb, coding_len + h_size);
+		if (err)
+			return NULL;
+	}
 
 	/* Create decoded unicast packet */
 	unicast_packet = (struct batadv_unicast_packet *)skb->data;