In the Linux kernel, the following vulnerability has been resolved:
cgroup/cpuset: rebind mm mempolicy to effective_mems, not mems_allowed
Creating a child cpuset where cpuset.mems is never set leads to a div/0 when a VMA mempolicy with MPOL_F_RELATIVE_NODES rebinds in response to a CPU hotplug event.
Reproduction steps: 1) Create a cgroup w/ cpuset controls (do not set cpuset.mems) 2) Move the task into the child cpuset 3) Create a VMA mempolicy for that task with MPOL_F_RELATIVE_NODES 4) unplug and hotplug a cpu echo 0 > /sys/devices/system/cpu/cpu1/online echo 1 > /sys/devices/system/cpu/cpu1/online 5) mempolicy rebind does a div/0 in mpol_relative_nodemask on the call to __nodes_fold()
The cpuset code passes (cs->mems_allowed) which is not guaranteed to have nodes to the rebind routine. Use cs->effective_mems instead, which is guaranteed to have a non-empty nodemask once we reach that code path.
[ david: add a comment, slightly rephrase description ]
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon_linux_2023 | — | Upgrade kernel-debuginfo-common-x86_64Upgrade kernelUpgrade kernel-modules-extra-commonUpgrade python3-perf-debuginfoUpgrade kernel-livepatch-6.1.180-225.360Upgrade bpftool-debuginfoUpgrade kernel-headersUpgrade kernel-debuginfo-common-aarch64Upgrade kernel-tools-debuginfoUpgrade kernel-develUpgrade kernel-debuginfoUpgrade bpftoolUpgrade kernel-modules-extraUpgrade kernel-toolsUpgrade perfUpgrade perf-debuginfoUpgrade python3-perfUpgrade kernel-tools-devel | Sep 1, 2026 | Aug 15, 2026 |
| Debian | — | Upgrade linux | Aug 16, 2026 | Aug 16, 2026 |
| Redhat_linux | — | No solution exists | Aug 19, 2026 | Aug 15, 2026 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Aug 25, 2026 | Aug 15, 2026 |
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