kernel: ipv4: NULL pointer dereference in ipv4_send_dest_unreach()

A NULL pointer dereference flaw was found in the Linux kernel ipv4 stack. The socket buffer skb was assumed to be associated with a device before calling ipoptionscompile, which is not always the case if the skb is re-routed by ipvs. This issue may allow a local user with CAPNETADMIN privileges t...