kernel: sched/fair: Fix fault in reweight_entity

In the Linux kernel, the following vulnerability has been resolved: sched/fair: Fix fault in reweightentity Syzbot found a GPF in reweightentity. This has been bisected to commit 4ef0c5c6b5ba "kernel/sched: Fix schedfork access an invalid schedtaskgroup" There is a race between schedpostfork and...