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

> A local attacker can trigger a kernel panic via madvise, causing a denial of service in the Linux kernel.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Mar 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47090, GHSA-2xp4-9hmm-63gj, UBUNTU-CVE-2021-47090

## What is CVE-2021-47090?

CVE-2021-47090 is a medium-severity vulnerability in Linux kernel, published on 4 Mar 2024. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

## Which versions are affected by CVE-2021-47090?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47090?

Apply the vendor's patch.

## Is CVE-2021-47090 being exploited?

There is no known exploitation of CVE-2021-47090 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-47090 and fix it if it is affected.

What it is: CVE-2021-47090 is a medium-severity vulnerability in Linux kernel, published on 4 Mar 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-47090 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-47090/ (Markdown: https://insights.sbomify.com/CVE-2021-47090/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47090
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47090
- OSV: https://osv.dev/vulnerability/CVE-2021-47090

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47090/
Summaries are generated and may contain mistakes; the official description above is the record.