In the Linux kernel, the following vulnerability has been resolved: sched: Fix yet more sched_fork() races Where commit 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid sched_task_group") fixed a fork race vs cgroup, it opened up a race vs syscalls by not placing the task on the runqueue before it gets exposed through the pidhash. Commit 13765de8148f ("sched/fair: Fix fault in reweight_entity") is trying to fix a single instance of this, instead fix the whole class of issues, effectively reverting this commit.
https://git.kernel.org/stable/c/c65cfd89cef669d90c59f3bf150af6458137a04f
https://git.kernel.org/stable/c/b1e8206582f9d680cff7d04828708c8b6ab32957
https://git.kernel.org/stable/c/3411613611a5cddf7e80908010dc87cb527dd13b