CVE-2024-42094

What it actually does

The flaw allows explicit allocation of a cpumask variable on the kernel stack in the iucv networking code path, which can trigger stack overflow when CONFIG_CPUMASK_OFFSTACK=y, leading to memory corruption.

Why it matters to the business

Linux systems may experience kernel instability, crashes, or information disclosure, potentially disrupting services and requiring urgent patching across server fleets and embedded devices.

How an attack unfolds

An attacker with local access triggers the vulnerable iucv code path to force stack-based cpumask allocation, overflowing the stack to corrupt adjacent memory and achieve denial of service or limited information exposure.

How to fix it

Update the Linux kernel to the fixed commit 2b085521be5292016097b5e7ca81b26be3f7098d or later stable releases that use cpumask_var APIs for allocation.

How to confirm the fix worked

Verify the running kernel includes commit 2b085521be5292016097b5e7ca81b26be3f7098d via git log or kernel version checks, and test iucv code paths under CONFIG_CPUMASK_OFFSTACK=y.

Typical attack path

1. Obtain local user access on a vulnerable Linux kernel
2. Trigger iucv networking operations that invoke the cpumask allocation
3. Cause stack overflow leading to memory corruption
4. Leverage corruption for crash or information leak

How to detect it

Inspect kernel logs for stack overflow warnings or oops messages involving iucv and cpumask allocation; correlate with local process activity on affected kernels.

What your security team should do

• Prioritize kernel upgrades to the fixed commit across all affected systems
• Review CONFIG_CPUMASK_OFFSTACK settings in kernel builds
• Monitor for local privilege escalation attempts targeting kernel networking