{"id":"CVE-2026-98542","published":"2026-10-18T16:17:06.090","lastModified":"2026-10-19T10:19:10.107","description":"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\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.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/0751ab665cb3dcdac224b002565f2e28461740d5","tags":[]},{"url":"https://git.kernel.org/stable/c/241e67b60308cdce25bba66616a109759edd1d40","tags":[]},{"url":"https://git.kernel.org/stable/c/31c88350b7dd1522792f726f79607f31bb55c50f","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}