Description
In the Linux kernel, the following vulnerability has been resolved:
mm/page_vma_mapped: fix device-private PMD handling
Commit 65edfda6f3f2 ("mm/rmap: extend rmap and migration support
device-private entries") introduced the concept of device-private PMD
entries, but did not correctly update the rmap walk code to account for
them.
As a result, when page_vma_mapped_walk() encounters device-private PMD
entries, it takes no action other than to acquire the PMD lock and exit.
However this is highly problematic for two reasons - firstly, device
private entries possess a PFN so check_pmd() needs to be called to ensure
an overlapping PFN range.
Secondly, and more importantly, if PVMW_MIGRATION is set the caller
assumes the returned entry is a migration entry, resulting in memory
corruption when the caller tries to interpret the device private entry as
such.
In addition, commit 146287290023 ("mm/huge_memory: implement
device-private THP splitting") allowed device private PMDs to be split
like THP mappings, but again did not update this code path.
As a result, we might race a PMD split prior to acquiring the PMD lock.
This patch addresses all of these issues by invoking check_pmd(), ensuring
PMVW_MIGRATION is not set and checks whether a split raced us we do for
PMD THP and migration entries.
Instead of checking for a subset of the cases after taking the pmd_lock(),
put device-private along with pmd_trans_huge() and
pmd_is_migration_entry(). Also remove thp_migration_supported() as it is
already guarded by pmd_is_migration_entry().
[akpm@linux-foundation.org: fix Raspberry Pi 1 build, per David]
mm/page_vma_mapped: fix device-private PMD handling
Commit 65edfda6f3f2 ("mm/rmap: extend rmap and migration support
device-private entries") introduced the concept of device-private PMD
entries, but did not correctly update the rmap walk code to account for
them.
As a result, when page_vma_mapped_walk() encounters device-private PMD
entries, it takes no action other than to acquire the PMD lock and exit.
However this is highly problematic for two reasons - firstly, device
private entries possess a PFN so check_pmd() needs to be called to ensure
an overlapping PFN range.
Secondly, and more importantly, if PVMW_MIGRATION is set the caller
assumes the returned entry is a migration entry, resulting in memory
corruption when the caller tries to interpret the device private entry as
such.
In addition, commit 146287290023 ("mm/huge_memory: implement
device-private THP splitting") allowed device private PMDs to be split
like THP mappings, but again did not update this code path.
As a result, we might race a PMD split prior to acquiring the PMD lock.
This patch addresses all of these issues by invoking check_pmd(), ensuring
PMVW_MIGRATION is not set and checks whether a split raced us we do for
PMD THP and migration entries.
Instead of checking for a subset of the cases after taking the pmd_lock(),
put device-private along with pmd_trans_huge() and
pmd_is_migration_entry(). Also remove thp_migration_supported() as it is
already guarded by pmd_is_migration_entry().
[akpm@linux-foundation.org: fix Raspberry Pi 1 build, per David]
Published:
2026-08-10
Score:
n/a
EPSS:
n/a
KEV:
No
Impact:
n/a
Action:
n/a
Analysis
Analysis and contextual insights are available on OpenCVE Cloud.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
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| Linux | Linux | affected |
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No data.
No data.
| Vendor | Product | Confidence | Versions | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux Kernel | 99% |
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| Linux | Linux Kernel | 99% |
|
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Remediation
No vendor fix or workaround currently provided.
Additional remediation guidance may be available on OpenCVE Cloud.
Tracking
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Advisories
No advisories yet.
References
History
Mon, 10 Aug 2026 12:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: mm/page_vma_mapped: fix device-private PMD handling Commit 65edfda6f3f2 ("mm/rmap: extend rmap and migration support device-private entries") introduced the concept of device-private PMD entries, but did not correctly update the rmap walk code to account for them. As a result, when page_vma_mapped_walk() encounters device-private PMD entries, it takes no action other than to acquire the PMD lock and exit. However this is highly problematic for two reasons - firstly, device private entries possess a PFN so check_pmd() needs to be called to ensure an overlapping PFN range. Secondly, and more importantly, if PVMW_MIGRATION is set the caller assumes the returned entry is a migration entry, resulting in memory corruption when the caller tries to interpret the device private entry as such. In addition, commit 146287290023 ("mm/huge_memory: implement device-private THP splitting") allowed device private PMDs to be split like THP mappings, but again did not update this code path. As a result, we might race a PMD split prior to acquiring the PMD lock. This patch addresses all of these issues by invoking check_pmd(), ensuring PMVW_MIGRATION is not set and checks whether a split raced us we do for PMD THP and migration entries. Instead of checking for a subset of the cases after taking the pmd_lock(), put device-private along with pmd_trans_huge() and pmd_is_migration_entry(). Also remove thp_migration_supported() as it is already guarded by pmd_is_migration_entry(). [akpm@linux-foundation.org: fix Raspberry Pi 1 build, per David] | |
| Title | mm/page_vma_mapped: fix device-private PMD handling | |
| 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: 2026-08-10T11:59:30.633Z
Reserved: 2026-07-30T09:28:09.372Z
Link: CVE-2026-68163
Vulnrichment
No data.
NVD
No data.
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-08-10T16:15:04Z
Weaknesses
No weakness.