Copyright © 2012 Red Hat, Inc. All rights reserved. Low 2026-10-18T00:00:00 kernel: mm/damon/vaddr: avoid hw-driven pte updates during damon_hugetlb_mkold() 1.9 CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:N CWE-821

In the Linux kernel, the following vulnerability has been resolved: mm/damon/vaddr: avoid hw-driven pte updates during damon_hugetlb_mkold() damon_hugetlb_mkold() reads the page table entry into a local variable, unsets the accessed bit in the variable, and updates the page table entry with the updated variable value. If hardware updates the same page table entry in parallel, the hw updates could be lost. For example, hardware-updated dirty bits might be lost. Avoid the parallel updates by clearing the page table entry when reading it together, using huge_ptep_get_and_clear(). If a parallel write to the memory is made after the clearing, the hw will see the page table entry is cleared, trigger page fault and wait until it is handled. The page fault handling will wait for damon_hugetlb_mkold() due to the page table lock. Because hugetlbfs is an in-memory file system and hugetlb pages cannot be reclaimed, no critical issue is expected to my best knowledge. But definitely this is a nasty bug that should be fixed sooner rather than later. The issue was discovered [1] by Sashiko.

A flaw was found in the Linux kernel. A race condition within the Data Access Monitor (DAMON) subsystem allows hardware-driven page table updates to be lost during the monitoring of huge memory pages. A local user running processes monitored by DAMON can trigger concurrent memory operations, resulting in inconsistent memory state and unexpected system behavior.

This vulnerability is rated as Low severity because triggering the race condition requires administrative privileges to initiate memory profiling and cannot be directly leveraged for privilege escalation. In standard Red Hat Enterprise Linux deployments, the Data Access Monitor framework is not active by default and requires privileged access to configure. Moreover, the potential loss of page table updates is restricted to hugetlbfs mappings, which are non-reclaimable in-memory pages, limiting the overall consequence to subtle memory state discrepancies rather than critical system failure. Red Hat Enterprise Linux 10 Fix deferred kernel Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel-rt Red Hat Enterprise Linux 8 Fix deferred kernel Red Hat Enterprise Linux 8 Fix deferred kernel-rt Red Hat Enterprise Linux 9 Fix deferred kernel Red Hat Enterprise Linux 9 Fix deferred kernel-rt Red Hat OpenShift Container Platform 4 Not affected openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 Fix deferred openshift/ose-rhel-coreos-9 https://www.cve.org/CVERecord?id=CVE-2026-98505 https://nvd.nist.gov/vuln/detail/CVE-2026-98505 https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98505.mbox