CVE-2024-27031 – A race condition vulnerability in the Linux ker... (How to Fix)

Q: What is the severity of CVE-2024-27031?

CVE-2024-27031 has a CVSS score of 5.5 (MEDIUM). A race condition vulnerability in the Linux kernel's NFS client implementation could cause a deadlock when processing read operations while writeback interrupts occur. This affects systems using NFS mounts with specific configurations, potentially leading to system instability or denial of service. The issue is triggered during concurrent read and write operations on NFS-mounted filesystems.

📋 TL;DR

A race condition vulnerability in the Linux kernel's NFS client implementation could cause a deadlock when processing read operations while writeback interrupts occur. This affects systems using NFS mounts with specific configurations, potentially leading to system instability or denial of service. The issue is triggered during concurrent read and write operations on NFS-mounted filesystems.

💻 Affected Systems

Products:

Linux kernel

Versions: Kernel versions with NFS client and netfs support, specifically around 6.7.x series (exact range depends on backports)

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ✅ No

Notes: Only vulnerable when using NFS mounts with specific configurations (NFSv3 with fsc option shown in reproduction steps). Requires concurrent read/write operations to trigger.

📦 What is this software?

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

⚠️ Risk & Real-World Impact

🔴

Worst Case

System deadlock requiring reboot, causing denial of service for NFS-mounted filesystems and potentially affecting system stability.

🟠

Likely Case

Occasional system hangs or performance degradation during heavy NFS I/O operations, particularly with concurrent reads and writes.

🟢

If Mitigated

Minor performance impact or no noticeable effect if NFS is not heavily used or if the specific code path isn't triggered.

🌐 Internet-Facing: LOW - Requires NFS mounts and specific I/O patterns; not directly exploitable over network without existing NFS access.

🏢 Internal Only: MEDIUM - Internal systems using NFS mounts for shared storage could experience service disruption during heavy I/O workloads.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: NO

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

The provided test case demonstrates reliable reproduction but requires local access and specific NFS mount configuration. Not weaponized for remote exploitation.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Patched in kernel commits: 8a2e5977cecd3cde6a0e3e86b7b914d00240e5dc and related backports

Vendor Advisory: https://git.kernel.org/stable/c/8a2e5977cecd3cde6a0e3e86b7b914d00240e5dc

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version from your distribution. 2. Check kernel version with 'uname -r'. 3. Reboot system after kernel update. 4. Verify fix with reproduction test.

🔧 Temporary Workarounds

Avoid NFS fsc mounts

linux

Disable fsc (file system cache) option on NFS mounts to avoid the vulnerable code path

mount -o vers=3 127.0.0.1:/export /mnt/nfs # without fsc option

Limit concurrent I/O

all

Reduce simultaneous read/write operations on NFS-mounted filesystems

🧯 If You Can't Patch

Monitor NFS mounts for performance issues and restart services if deadlocks occur
Implement load balancing to distribute NFS I/O across multiple mounts or servers

🔍 How to Verify

Check if Vulnerable:

Run reproduction test: mount NFS with fsc, create file, drop caches, read file while monitoring for lockdep warnings

Check Version:

uname -r

Verify Fix Applied:

After patching, run same reproduction test and ensure no lockdep warnings appear in dmesg

📡 Detection & Monitoring

Log Indicators:

Kernel lockdep warnings in dmesg about xa_lock deadlocks
System hangs during NFS operations
Increased I/O wait times on NFS mounts

Network Indicators:

Increased NFS timeout errors
Unusual NFS protocol retransmissions

SIEM Query:

source="kernel" AND "WARNING: inconsistent lock state" AND "xa_lock"

📊 Metadata

CVE ID: CVE-2024-27031

CVSS v3 Score: 5.5 (MEDIUM)

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CWE: CWE-667

Published: May 1, 2024

Last Updated: December 23, 2024

🔗 References

📤 Share & Export

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🔗 Related Vulnerabilities

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