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CVE Record

CVE-2021-47090: mm/hwpoison: clear MF_COUNT_INCREASED before retrying get_any_page()

In the Linux kernel, the following vulnerability has been resolved: mm/hwpoison: clear MF_COUNT_INCREASED before retrying get_any_page() Hulk Robot reported a panic in put_page_testzero() when testing madvise() with MADV_SOFT_OFFLINE. The BUG() is triggered when retrying get_any_page(). This is because we keep MF_COUNT_INCREASED flag in second try but the refcnt is not increased. page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0) ------------[ cut here ]------------ kernel BUG at include/linux/mm.h:737! invalid opcode: 0000 [#1] PREEMPT SMP CPU: 5 PID: 2135 Comm: sshd Tainted: G B 5.16.0-rc6-dirty #373 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 RIP: release_pages+0x53f/0x840 Call Trace: free_pages_and_swap_cache+0x64/0x80 tlb_flush_mmu+0x6f/0x220 unmap_page_range+0xe6c/0x12c0 unmap_single_vma+0x90/0x170 unmap_vmas+0xc4/0x180 exit_mmap+0xde/0x3a0 mmput+0xa3/0x250 do_exit+0x564/0x1470 do_group_exit+0x3b/0x100 __do_sys_exit_group+0x13/0x20 __x64_sys_exit_group+0x16/0x20 do_syscall_64+0x34/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae Modules linked in: ---[ end trace e99579b570fe0649 ]--- RIP: 0010:release_pages+0x53f/0x840

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel flaw can crash a system during memory failure handling tested through MADV_SOFT_OFFLINE. The public record describes a kernel panic caused by incorrect page reference accounting during a retry path. No CVSS score, KEV listing, or public exploitation evidence is provided in the bundle.

Executive priority

Treat this as a patch-management item with possible availability impact. It is not justified as emergency internet-facing risk from the provided evidence, but affected Linux fleets should be updated through normal kernel maintenance windows.

Technical view

In mm/hwpoison, MF_COUNT_INCREASED was not cleared before retrying get_any_page(). On retry, the flag incorrectly implied a page reference count increase, leading to put_page_testzero()/release_pages BUG conditions when the reference count was zero.

Likely exposure

Exposure is limited to Linux kernels in the affected ranges listed by the CVE source, including 5.10, 5.10.89, 5.15.12, and 5.16 entries. The bundle does not define distribution package names, remote reachability, or privilege requirements.

Exploitation context

The source describes discovery by Hulk Robot while testing madvise() with MADV_SOFT_OFFLINE. It provides crash traces but no proof of active exploitation, no KEV status, and no weaponized exploit information.

Researcher notes

The evidence supports a kernel BUG from stale MF_COUNT_INCREASED state in the hwpoison retry path. Impact beyond local denial of service is not established in the bundle. Version range interpretation should be confirmed against Linux stable and downstream distro metadata.

Mitigation direction

  • Inventory Linux kernel versions across servers, appliances, and base images.
  • Apply vendor kernel updates that include the referenced stable Linux fixes.
  • Check distribution advisories for backported fixes and package-specific version mapping.
  • Prioritize systems allowing untrusted local workloads until vendor guidance clarifies impact.

Validation and detection

  • Confirm running kernel versions against vendor advisories and the CVE record.
  • Verify updated kernels include one of the referenced stable commits or a vendor backport.
  • Review crash logs for release_pages, put_page_testzero, or MADV_SOFT_OFFLINE-related panics.
  • Document any systems deferred from patching and their compensating controls.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2021-47090 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
2ADP providers
4Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxb94e02822debdf0cc473556aad7dcc859f216653, b94e02822debdf0cc473556aad7dcc859f216653, b94e02822debdf0cc473556aad7dcc859f216653unaffected
LinuxLinux5.10, 0, 5.10.89, 5.15.12, 5.16affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.