CVE-2025-40270

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

mm, swap: fix potential UAF issue for VMA readahead

Since commit 78524b05f1a3 ("mm, swap: avoid redundant swap device

pinning"), the common helper for allocating and preparing a folio in the

swap cache layer no longer tries to get a swap device reference

internally, because all callers of __read_swap_cache_async are already

holding a swap entry reference. The repeated swap device pinning isn't

needed on the same swap device.

Caller of VMA readahead is also holding a reference to the target entry's

swap device, but VMA readahead walks the page table, so it might encounter

swap entries from other devices, and call __read_swap_cache_async on

another device without holding a reference to it.

So it is possible to cause a UAF when swapoff of device A raced with

swapin on device B, and VMA readahead tries to read swap entries from

device A. It's not easy to trigger, but in theory, it could cause real

issues.

Make VMA r

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References