{"id":"CVE-2026-98542","title":"cgroup/cpuset: Return PERR_NOCPUS in remote_partition_enable() on subpartitions_cpus conflict","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\ncgroup/cpuset: Return PERR_NOCPUS in remote_partition_enable() on subpartitions_cpus conflict\n\nWhen a remote partition is created underneath an existing local partition…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 86888c7bd117c29eab169c37e5f6bbbf583da983 < 241e67b60308cdce25bba66616a109759edd1d40","Linux >= 86888c7bd117c29eab169c37e5f6bbbf583da983 < 0751ab665cb3dcdac224b002565f2e28461740d5","Linux >= 86888c7bd117c29eab169c37e5f6bbbf583da983 < 31c88350b7dd1522792f726f79607f31bb55c50f","Linux 6.16"],"published":"2026-10-18","updated":"2026-10-18","sourceUpdated":"2026-10-18T15:18:10.035Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98542","references":[{"url":"https://git.kernel.org/stable/c/241e67b60308cdce25bba66616a109759edd1d40"},{"url":"https://git.kernel.org/stable/c/0751ab665cb3dcdac224b002565f2e28461740d5"},{"url":"https://git.kernel.org/stable/c/31c88350b7dd1522792f726f79607f31bb55c50f"}],"tags":["cve.org"],"ingestedAt":"2026-10-18T15:45:12.268Z","slug":"CVE-2026-98542","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\ncgroup/cpuset: Return PERR_NOCPUS in remote_partition_enable() on subpartitions_cpus conflict\n\nWhen a remote partition is created underneath an existing local partition\nvia a non-partition (PRS_MEMBER) intermediate cgroup, update_prstate() sees\nparent->partition_root_state == PRS_MEMBER and calls\nremote_partition_enable().\n\nCommit 86888c7bd117 (\"cgroup/cpuset: Add warnings to catch inconsistency\nin exclusive CPUs\") replaced the cpumask_intersects(tmp->new_cpus,\nsubpartitions_cpus) error check in remote_partition_enable() with\nWARN_ON_ONCE(). As a result, remote_partition_enable() emits a warning\nand proceeds to enable the remote partition on CPUs that are already\nowned by the ancestor local partition in subpartitions_cpus.\n\nThis can be reproduced on Linux 7.3.0-rc3 with:\n\n  mkdir -p /tmp/cg1\n  mount -t cgroup2 none /tmp/cg1\n  echo \"+cpuset\" > /tmp/cg1/cgroup.subtree_control\n\n  mkdir /tmp/cg1/A\n  echo 1 > /tmp/cg1/A/cpuset.cpus\n  echo 1 > /tmp/cg1/A/cpuset.cpus.exclusive\n  echo root > /tmp/cg1/A/cpuset.cpus.partition\n  echo \"+cpuset\" > /tmp/cg1/A/cgroup.subtree_control\n\n  mkdir /tmp/cg1/A/B\n  echo 1 > /tmp/cg1/A/B/cpuset.cpus\n  echo 1 > /tmp/cg1/A/B/cpuset.cpus.exclusive\n  echo \"+cpuset\" > /tmp/cg1/A/B/cgroup.subtree_control\n\n  mkdir /tmp/cg1/A/B/D\n  echo 1 > /tmp/cg1/A/B/D/cpuset.cpus\n  echo 1 > /tmp/cg1/A/B/D/cpuset.cpus.exclusive\n  echo root > /tmp/cg1/A/B/D/cpuset.cpus.partition\n\nwhich triggers:\n\n  WARNING: kernel/cgroup/cpuset.c:1594 at remote_partition_enable+0x1c1/0x300\n\nand leaves both /tmp/cg1/A and /tmp/cg1/A/B/D as active root partitions\nclaiming exclusive CPU 1.\n\nFix this by returning PERR_NOCPUS when tmp->new_cpus intersects\nsubpartitions_cpus in remote_partition_enable(), matching the error code\nused by remote_cpus_update() for the same subpartitions_cpus conflict, and\nadd a regression test case to\ntools/testing/selftests/cgroup/test_cpuset_prs.sh.\n\nTested in QEMU on Linux 7.3.0-rc3 using the reproducer above and\ntools/testing/selftests/cgroup/test_cpuset_prs.sh.\n\n## Affected\n\n- `Linux >= 86888c7bd117c29eab169c37e5f6bbbf583da983 < 241e67b60308cdce25bba66616a109759edd1d40`\n- `Linux >= 86888c7bd117c29eab169c37e5f6bbbf583da983 < 0751ab665cb3dcdac224b002565f2e28461740d5`\n- `Linux >= 86888c7bd117c29eab169c37e5f6bbbf583da983 < 31c88350b7dd1522792f726f79607f31bb55c50f`\n- `Linux 6.16`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}