CVE-2025-39839 batman-adv: fix OOB read/write in network-coding decode

In the Linux kernel, the following vulnerability has been resolved: batman-adv: fix OOB read/write in network-coding decode batadvncskbdecodepacket trusts codedlen and checks only against skb-len. XOR starts at sizeofstruct batadvunicastpacket, reducing payload headroom, and the source skb length...