Bug 2559748 (CVE-2026-98972)

Summary: CVE-2026-98972 kernel: cgroup/cpuset: Don't access cpuset_cgrp_subsys.root in is_in_v2_mode()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in the Linux kernel. A local user could trigger a use-after-free vulnerability when a control group (cgroup) filesystem is rebound, causing the cpuset subsystem to access a stale pointer. This flaw can lead to a Denial of Service (DoS) by crashing the system or potentially allow privilege escalation.
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Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-10-23 13:29:31 UTC 
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