In the Linux kernel, the following vulnerability has been resolved:
bfq: Make sure bfqg for which we are queueing requests is online
Bios queued into BFQ IO scheduler can be associated with a cgroup that was already offlined. This may then cause insertion of this bfqgroup into a service tree. But this bfqgroup will get freed as soon as last bio associated with it is completed leading to use after free issues for service tree users. Fix the problem by making sure we always operate on online bfqgroup. If the bfqgroup associated with the bio is not online, we pick the first online parent.