CVE-2026-98972

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

cgroup/cpuset: Don't access cpuset cgrp subsys.root in is in v2 mode()

After seeing the patch [1] to guard is in v2 mode() with RCU, it makes me realize that is in v2 mode() may be called in a context where a new cgroup filesystem is being rebound with stale cpuset cgrp subsys.root pointer. Avoid this potential UaF situation by adding a new cpuset v2 mode flag which is set when the cpuset v2 mode mount option is used. This flag is written into only when cpuset bind() is being called with a stable cpuset cgrp subsys.root value. The is in v2 mode() helper is modified to read the new cpuset v2 mode flag instead of accessing cpuset cgrp subsys.root directly.

[1] https://lore.kernel.org/lkml/20260929084124.626693-2-arighi@nvidia.com