CVE-2026-80977 net: skbuff: don't touch shared zerocopy state in skb_tx_error()

In the Linux kernel, the following vulnerability has been resolved: net: skbuff: don't touch shared zerocopy state in skbtxerror skbtxerror completes the zerocopy uarg and clears SKBFLALLZEROCOPY, and skbzcopydowngrademanaged clears SKBFLMANAGEDFRAGREFS. Both live in skbshinfo, which every clone...