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.
Analysis
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Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||
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| Linux | Linux | unaffected |
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| Linux | Linux | affected |
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No data available yet.
No solution or workaround provided in the CVE record.
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Tracking
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Sun, 18 Oct 2026 15:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | mm/damon/vaddr: avoid hw-driven pte updates during damon_hugetlb_mkold() | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-10-18T15:17:06.200Z
Reserved: 2026-09-25T10:25:14.353Z
Link: CVE-2026-98505
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-10-18T16:17:01.610
Modified: 2026-10-18T16:17:01.610
Link: CVE-2026-98505
Redhat
No data.
OpenCVE Enrichment
No data.
No weakness.