kernel: net/sched: cls_u32: use skb_header_pointer_careful()

In the Linux kernel, the following vulnerability has been resolved: net/sched: clsu32: use skbheaderpointercareful skbheaderpointer does not fully validate negative @offset values. Use skbheaderpointercareful instead. GangMin Kim provided a report and a repro fooling u32classify: BUG: KASAN:...