CVE-2026-72392 ipv6: fib6: fix NULL deref in fib6_walk_continue() on multi-batch dump

In the Linux kernel, the following vulnerability has been resolved: ipv6: fib6: fix NULL deref in fib6walkcontinue on multi-batch dump inet6dumpfib saves its progress in cb-args1 as a positional index within the current hash chain. Between batches, a concurrent fib6newtable can insert a new table...