# CVE-2026-90201: net: page_pool: fix UAF in __page_pool_release_netmem_dma on xa_cmpxchg race

> A race condition in the Linux kernel page pool allows a use-after-free, potentially leading to code execution or system crash.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-90201, DEBIAN-CVE-2026-90201, GHSA-6rvq-r5r4-hcv8, UBUNTU-CVE-2026-90201

## What is CVE-2026-90201?

CVE-2026-90201 is an use after free vulnerability in Linux, published on 17 Sep 2026. 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:

net: page_pool: fix UAF in __page_pool_release_netmem_dma on xa_cmpxchg race

This bug was discovered while testing the hns3 driver under channel
reconfiguration (`ethtool -L` / `ethtool -G`) with iperf3 traffic on
arm64. The race is intermittently triggered when page_pool_destroy()
runs page_pool_scrub() concurrently with page return via
page_pool_put_netmem() on a different CPU. A WARN in
page_pool_clear_pp_info() surfaced the dangling DMA index bits left
by the cmpxchg loser, which led to the investigation.

page_pool_scrub() iterates pool->dma_mapped via xa_for_each() with no
page ref held. __page_pool_release_netmem_dma() currently reads and
writes netmem fields (dma_addr, DMA index bits in pp_magic) after
xa_cmpxchg() returns. The unref path calls put_page() unconditionally
regardless of the cmpxchg outcome; when it loses the cmpxchg, it still
frees the page before the scrub winner finishes these netmem accesses,
so scrub touches a freed page -- a Use-After-Free.

Fix this by splitting the DMA release into two functions:

1. __page_pool_unmap_netmem_dma() caches dma_addr before xa_cmpxchg(),
   does the cmpxchg to remove the DMA mapping, and calls dma_unmap on
   the cached address. It never touches netmem fields after the cmpxchg,
   making it safe for the scrub path which holds no page ref.

2. __page_pool_release_netmem_dma() wraps the above and additionally
   clears dma_addr and DMA index bits in netmem fields. This is safe
   only when the caller holds a page ref, so it is used by the return
   path (page_pool_return_netmem).

The scrub path calls __page_pool_unmap_netmem_dma() directly; the return
path calls __page_pool_release_netmem_dma().

## Which versions are affected by CVE-2026-90201?


## How do I fix CVE-2026-90201?

Apply the vendor's patch.

## Is CVE-2026-90201 being exploited?

There is no known exploitation of CVE-2026-90201 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90201 and fix it if it is affected.

What it is: CVE-2026-90201 is an use after free vulnerability in Linux, published on 17 Sep 2026. 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-2026-90201 in the wild and no public exploit code.

Affected product: Linux. 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-2026-90201/ (Markdown: https://insights.sbomify.com/CVE-2026-90201/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90201
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90201
- OSV: https://osv.dev/vulnerability/CVE-2026-90201

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90201/
Summaries are generated and may contain mistakes; the official description above is the record.