In the Linux kernel, the following vulnerability has been resolved:
mm/userfaultfd: fix kmap_local LIFO ordering for CONFIG_HIGHPTE
With CONFIG_HIGHPTE on 32-bit ARM, move_pages_pte() maps PTE pages using
kmap_local_page(), which requires unmapping in Last-In-First-Out order.
The current code maps dst_pte first, then src_pte, but unmaps them in the
same order (dst_pte, src_pte), violating the LIFO requirement. This
causes the warning in kunmap_local_indexed():
WARNING: CPU: 0 PID: 604 at mm/highmem.c:622 kunmap_local_indexed+0x178/0x17c
addr \!= __fix_to_virt(FIX_KMAP_BEGIN + idx)
Fix this by reversing the unmap order to respect LIFO ordering.
This issue follows the same pattern as similar fixes:
- commit eca6828403b8 ("crypto: skcipher - fix mismatch between mapping and unmapping order")
- commit 8cf57c6df818 ("nilfs2: eliminate staggered calls to kunmap in nilfs_rename")
Both of which addressed the same fundamental requirement that kmap_local
operations must follow LIFO ordering.
mm/userfaultfd: fix kmap_local LIFO ordering for CONFIG_HIGHPTE
With CONFIG_HIGHPTE on 32-bit ARM, move_pages_pte() maps PTE pages using
kmap_local_page(), which requires unmapping in Last-In-First-Out order.
The current code maps dst_pte first, then src_pte, but unmaps them in the
same order (dst_pte, src_pte), violating the LIFO requirement. This
causes the warning in kunmap_local_indexed():
WARNING: CPU: 0 PID: 604 at mm/highmem.c:622 kunmap_local_indexed+0x178/0x17c
addr \!= __fix_to_virt(FIX_KMAP_BEGIN + idx)
Fix this by reversing the unmap order to respect LIFO ordering.
This issue follows the same pattern as similar fixes:
- commit eca6828403b8 ("crypto: skcipher - fix mismatch between mapping and unmapping order")
- commit 8cf57c6df818 ("nilfs2: eliminate staggered calls to kunmap in nilfs_rename")
Both of which addressed the same fundamental requirement that kmap_local
operations must follow LIFO ordering.
Metrics
Affected Vendors & Products
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Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Wed, 01 Oct 2025 07:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: mm/userfaultfd: fix kmap_local LIFO ordering for CONFIG_HIGHPTE With CONFIG_HIGHPTE on 32-bit ARM, move_pages_pte() maps PTE pages using kmap_local_page(), which requires unmapping in Last-In-First-Out order. The current code maps dst_pte first, then src_pte, but unmaps them in the same order (dst_pte, src_pte), violating the LIFO requirement. This causes the warning in kunmap_local_indexed(): WARNING: CPU: 0 PID: 604 at mm/highmem.c:622 kunmap_local_indexed+0x178/0x17c addr \!= __fix_to_virt(FIX_KMAP_BEGIN + idx) Fix this by reversing the unmap order to respect LIFO ordering. This issue follows the same pattern as similar fixes: - commit eca6828403b8 ("crypto: skcipher - fix mismatch between mapping and unmapping order") - commit 8cf57c6df818 ("nilfs2: eliminate staggered calls to kunmap in nilfs_rename") Both of which addressed the same fundamental requirement that kmap_local operations must follow LIFO ordering. | |
| Title | mm/userfaultfd: fix kmap_local LIFO ordering for CONFIG_HIGHPTE | |
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2025-10-01T07:42:47.100Z
Reserved: 2025-04-16T07:20:57.146Z
Link: CVE-2025-39899
Vulnrichment
No data.
NVD
Status : Received
Published: 2025-10-01T08:15:32.620
Modified: 2025-10-01T08:15:32.620
Link: CVE-2025-39899
Redhat
No data.
OpenCVE Enrichment
No data.