kernel: net: core: reject skb_copy(_expand) for fraglist GSO skbs

In the Linux kernel, the following vulnerability has been resolved: net: core: reject skbcopyexpand for fraglist GSO skbs SKBGSOFRAGLIST skbs must not be linearized, otherwise they become invalid. Return NULL if such an skb is passed to skbcopy or skbcopyexpand, in order to prevent a crash on a...