cgroup/cpuset: Handle cpu hotplug race in guarantee_active_cpus()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-99065
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-23 13:17:30 UTC
Updated2026-10-23 13:17:30 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: cgroup/cpuset: Handle cpu hotplug race in guarantee_active_cpus() With commit 2125c0034c5d ("cgroup/cpuset: Make cpuset hotplug processing synchronous"), the cpuset hotplug operation becomes synchronous. That commit also removes the code that handles race between cpuset_hotplug_work and cpu hotplug notifier with the assumption that race is now gone. Later commit 7a0aabd9ce69 ("cgroup/cpuset: Always use cpu_active_mask") updates the cpuset code to always use cpu_active_mask instead of cpu_online_mask in some places including guarantee_online_cpus() which is renamed to guarantee_active_cpus() in that commit. In the case of CPU offline operation, cpu_active_mask is updated first in sched_cpu_deactivate() to remove the offline CPU before cpuset_handle_hotplug() is called to update the effective_cpus of the affected cpusets. The cpu_online_mask is updated after that near the end of the offline operation to remove the offline CPU. As a result, the race comes back and the top cpuset may not have any active CPU leading to NULL pointer dereference during the race window when guarantee_active_cpus() is called after cpu_active_mask is updated to remove the CPU to be torn down but before cpuset_handle_hotplug() is able to properly update the effective_cpus of the top cpuset. Fix this by adding back the NULL cs check to avoid this problem.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 7a0aabd9ce697fc581ec691b21f748050fbcf004 8d88d3221204fbb1b6dc2c0f2f2181fe49126639 git Not specified
CNA Linux Linux affected 7a0aabd9ce697fc581ec691b21f748050fbcf004 a21c255159bfe0034740292e10d2e258feeeb10d git Not specified
CNA Linux Linux affected 7a0aabd9ce697fc581ec691b21f748050fbcf004 23b1ab15ca91f2cffaf149d9bb0fafeb700c7db2 git Not specified
CNA Linux Linux affected 6.16 Not specified
CNA Linux Linux unaffected 6.16 semver Not specified
CNA Linux Linux unaffected 6.18.57 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.11 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/8d88d3221204fbb1b6dc2c0f2f2181fe49126639 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a21c255159bfe0034740292e10d2e258feeeb10d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/23b1ab15ca91f2cffaf149d9bb0fafeb700c7db2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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