Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

sched: fix warning in sched_setaffinity

Commit 8f9ea86fdf99b added some logic to sched_setaffinity that included a WARN when a per-task affinity assignment races with a cpuset update.

Specifically, we can have a race where a cpuset update results in the task affinity no longer being a subset of the cpuset. That's fine; we have a fallback to instead use the cpuset mask. However, we have a WARN set up that will trigger if the cpuset mask has no overlap at all with the requested task affinity. This shouldn't be a warning condition; its trivial to create this condition.

Reproduced the warning by the following setup:

- $PID inside a cpuset cgroup - another thread repeatedly switching the cpuset cpus from 1-2 to just 1 - another thread repeatedly setting the $PID affinity (via taskset) to 2