batman-adv: Always initialize fragment header priority

commit fe77d825 upstream.

The batman-adv unuicast fragment header contains 3 bits for the priority of
the packet. These bits will be initialized when the skb->priority contains
a value between 256 and 263. But otherwise, the uninitialized bits from the
stack will be used.

Fixes: c0f25c80 ("batman-adv: Include frame priority in fragment header")
Signed-off-by: Sven Eckelmann <sven.eckelmann@open-mesh.com>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/batman-adv/fragmentation.c

@@ -484,6 +484,8 @@ int batadv_frag_send_packet(struct sk_buff *skb,
 	 */
 	if (skb->priority >= 256 && skb->priority <= 263)
 		frag_header.priority = skb->priority - 256;
+	else
+		frag_header.priority = 0;
 
 	ether_addr_copy(frag_header.orig, primary_if->net_dev->dev_addr);
 	ether_addr_copy(frag_header.dest, orig_node->orig);