CVE-2024-35988

What it actually does

Incorrect TASK_SIZE definition on 64-bit RISC-V NOMMU causes userspace access routines to fail when physical RAM exceeds 4G, resulting in spurious access errors or memory handling faults.

Why it matters to the business

Systems running Linux on 64-bit RISC-V without MMU and with more than 4 GB RAM may experience unexpected application failures or instability, increasing operational risk especially in embedded or resource-constrained deployments.

How an attack unfolds

An attacker with local access can trigger the flawed userspace access paths on affected NOMMU configurations by placing RAM above 4G, leading to access routine failures that manifest as crashes or denied operations without requiring external network access.

How to fix it

Update the Linux kernel to the fixed commit 04bf2e5f95c1a52e28a7567a507f926efe31c3b6 or later stable release containing the TASK_SIZE correction for RISC-V NOMMU.

How to confirm the fix worked

Confirm kernel source includes the TASK_SIZE fix for 64-bit NOMMU; test on hardware with >4G RAM to ensure userspace access routines no longer produce spurious failures.

Typical attack path

1. Identify 64-bit RISC-V NOMMU target with physical RAM above 4G
2. Gain local execution context via process or shell
3. Invoke userspace memory access routines that rely on TASK_SIZE
4. Trigger spurious failure in access checks due to incorrect limit

How to detect it

Review kernel logs and dmesg for userspace access routine failures on RISC-V NOMMU systems; correlate with hardware configurations reporting RAM above 4G.

What your security team should do

• Prioritize kernel upgrade on all 64-bit RISC-V NOMMU systems with >4G RAM
• Monitor for application crashes related to memory access on affected platforms
• Review downstream device images and rebuild with patched kernel