CVE-2022-2318: Linux Kernel Use-After-Free Vulnerability

CVE-2022-2318 Overview

CVE-2022-2318 is a Use-After-Free vulnerability in the Linux kernel's ROSE (Radio Amateur Telecommunications Society) protocol timer handling code located in net/rose/rose_timer.c. This vulnerability allows local attackers to crash the Linux kernel without requiring elevated privileges, resulting in a denial of service condition.

The flaw exists in how the ROSE protocol module manages timer handlers for socket operations. When timer handlers execute after associated socket structures have been freed, the kernel attempts to access invalid memory regions, leading to system instability and crashes.

Critical Impact

Local attackers can exploit this use-after-free vulnerability to crash the Linux kernel, causing complete system denial of service without requiring any special privileges.

Affected Products

• Linux Kernel (versions prior to 5.19-rc5)
• Debian Linux 10.0 and 11.0
• NetApp H300S, H500S, H700S, H410S, and H410C firmware

Discovery Timeline

• July 6, 2022 - CVE-2022-2318 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-2318

Vulnerability Analysis

This vulnerability is classified as CWE-416 (Use After Free), a memory corruption flaw that occurs when a program continues to use memory after it has been freed. In the context of CVE-2022-2318, the issue manifests in the ROSE protocol's timer management functions within the Linux kernel networking subsystem.

The ROSE protocol is a packet-switched protocol derived from X.25 and used in amateur radio networks. The vulnerable code path involves timer handlers (rose_heartbeat_expiry, rose_timer_expiry) that manage socket keep-alive and timeout operations. When these timer handlers fire after the associated socket structure has been deallocated, the kernel accesses freed memory, corrupting kernel data structures and triggering a system crash.

The vulnerability can be exploited locally, requiring low-privilege access but no user interaction. While the attack complexity is low, the impact is limited to availability—attackers cannot leverage this flaw to gain code execution or access confidential information.

Root Cause

The root cause lies in improper synchronization between socket destruction and timer management in the ROSE protocol implementation. The original code used del_timer() and add_timer() functions directly, which do not properly handle the reference counting needed to prevent use-after-free conditions.

When a socket is being destroyed, there's a race window where timer callbacks may still be pending or executing. If the timer fires after the socket structure is freed but before the timer is properly cancelled, the callback function dereferences invalid memory pointers.

Attack Vector

The attack vector is local, meaning an attacker must have local access to the system to exploit this vulnerability. The exploitation process involves:

1. Creating a ROSE protocol socket on a vulnerable Linux system
2. Triggering timer operations through socket activity
3. Racing the socket destruction with pending timer callbacks
4. The timer handler accesses freed socket memory, causing kernel crash

The following patch demonstrates the fix applied to address this vulnerability:

void rose_start_heartbeat(struct sock *sk)
{
-	del_timer(&sk->sk_timer);
+	sk_stop_timer(sk, &sk->sk_timer);

	sk->sk_timer.function = rose_heartbeat_expiry;
	sk->sk_timer.expires  = jiffies + 5 * HZ;

-	add_timer(&sk->sk_timer);
+	sk_reset_timer(sk, &sk->sk_timer, sk->sk_timer.expires);
}

void rose_start_t1timer(struct sock *sk)
{
	struct rose_sock *rose = rose_sk(sk);

-	del_timer(&rose->timer);
+	sk_stop_timer(sk, &rose->timer);

	rose->timer.function = rose_timer_expiry;
	rose->timer.expires  = jiffies + rose->t1;

-	add_timer(&rose->timer);
+	sk_reset_timer(sk, &rose->timer, rose->timer.expires);
}

void rose_start_t2timer(struct sock *sk)
{
	struct rose_sock *rose = rose_sk(sk);

Source: GitHub Linux Commit

The fix replaces direct timer manipulation functions (del_timer/add_timer) with socket-aware timer functions (sk_stop_timer/sk_reset_timer) that properly manage reference counting on the socket structure, preventing the use-after-free condition.

Detection Methods for CVE-2022-2318

Indicators of Compromise

• Unexpected kernel panics or system crashes related to ROSE network protocol operations
• Kernel oops messages referencing rose_timer_expiry, rose_heartbeat_expiry, or net/rose/rose_timer.c
• System logs showing memory corruption errors in networking subsystem components
• Repeated system reboots without apparent hardware failures on systems with ROSE protocol enabled

Detection Strategies

• Monitor kernel logs (dmesg, /var/log/kern.log) for panic traces involving ROSE timer functions
• Deploy kernel live patching solutions to detect and alert on vulnerable kernel versions
• Use SentinelOne Singularity platform to monitor for suspicious local exploitation attempts targeting kernel subsystems
• Implement system call monitoring to detect unusual ROSE protocol socket operations

Monitoring Recommendations

• Enable kernel crash dump analysis to capture forensic data during exploitation attempts
• Configure auditd rules to log ROSE protocol socket operations (AF_ROSE socket family)
• Monitor for processes loading the rose kernel module on systems where it should not be used
• Deploy endpoint detection and response (EDR) solutions capable of detecting kernel-level anomalies

How to Mitigate CVE-2022-2318

Immediate Actions Required

• Update Linux kernel to version 5.19-rc5 or later that includes the security fix
• Apply vendor-specific patches from Debian, NetApp, or your distribution vendor
• Disable or blacklist the ROSE kernel module if not required: echo "blacklist rose" >> /etc/modprobe.d/blacklist.conf
• Restrict local access to systems running vulnerable kernel versions until patching is complete

Patch Information

The vulnerability has been fixed in the upstream Linux kernel via commit 9cc02ede696272c5271a401e4f27c262359bc2f6. The fix replaces unsafe timer operations with socket-aware timer management functions that properly handle reference counting.

Vendor patches are available from:

• Debian Security Advisory DSA-5191
• Debian LTS Announcement
• NetApp Security Advisory

Workarounds

• Blacklist the ROSE kernel module on systems where amateur radio networking is not required
• Restrict local user access to reduce the attack surface for unprivileged exploitation
• Implement mandatory access control (SELinux/AppArmor) policies to limit ROSE protocol access
• Consider containerization with restricted kernel module access for vulnerable workloads

# Disable ROSE kernel module to mitigate the vulnerability
echo "blacklist rose" >> /etc/modprobe.d/blacklist-rose.conf
echo "install rose /bin/false" >> /etc/modprobe.d/blacklist-rose.conf

# Unload the module if currently loaded
rmmod rose 2>/dev/null || true

# Update module dependencies
depmod -a

# Verify module is blacklisted
modprobe -n -v rose