CVE-2024-42250

What it actually does

Missing spinlock protection during xarray iteration in the cachefiles poll routine allows concurrent modification of cachefiles_req structures even under RCU, leading to unsafe dereferences and potential kernel instability or denial of service.

Why it matters to the business

Systems using cachefiles for local caching may experience unexpected crashes or service interruptions, increasing operational risk especially on servers or devices running affected kernel versions; urgency remains low given absence from known exploitation lists and stable EPSS.

How an attack unfolds

An attacker with local access triggers the poll operation on cachefiles while concurrent operations modify the xarray, racing to dereference freed or altered cachefiles_req objects and causing a crash or undefined behavior.

How to fix it

Update the Linux kernel to a version containing commit 97cfd5e20ddc2e33e16ce369626ce76c9a475fd7 or later; rebuild and reboot with the patched kernel; for AlmaLinux 8 emacs packages, upgrade to version 1:26.1-7.el8 or newer.

How to confirm the fix worked

Verify the running kernel includes commit 97cfd5e20ddc2e33e16ce369626ce76c9a475fd7 via git log or uname; confirm package versions match the fixed releases; perform regression testing of cachefiles poll behavior under concurrent load.

Typical attack path

1. Obtain local user access on a vulnerable Linux system using cachefiles
2. Identify or create conditions that invoke the cachefiles poll routine
3. Trigger concurrent modifications to the xarray from other processes or threads
4. Cause the poll iteration to dereference an unprotected structure
5. Result in kernel panic or denial of service

How to detect it

Review kernel logs for cachefiles-related oops or panic messages around poll operations; examine system call traces involving cachefiles for unusual concurrent activity; no widespread exploitation indicators are currently known.

What your security team should do

• Prioritize kernel updates on all systems exposing cachefiles functionality
• Monitor vendor advisories for backported fixes in distribution kernels
• Apply the patch or upgrade within standard maintenance windows given moderate CVSS and lack of KEV listing
• Review local use of cachefiles and consider disabling if the workload permits until patched