CVE-2026-98972cgroup/cpuset: Don't access cpuset_cgrp_subsys.root in is_in_v2_mode()

Official description

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

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/988bf67a13890a37a33201f95947095ca9bec856
• https://git.kernel.org/stable/c/e06b678e3b4e12fdaa0b51a7a5a54abc5dbd6469