CVE-2022-1678: Linux Kernel Information Disclosure Flaw

CVE-2022-1678 Overview

CVE-2022-1678 is a memory leak vulnerability discovered in the Linux Kernel affecting versions 4.18 to 4.19. The flaw exists in the TCP pacing implementation where an improper update of socket references can lead to memory and network namespace (netns) leaks. This vulnerability can be exploited by remote clients to cause resource exhaustion on affected systems.

Critical Impact

Remote attackers can exploit this TCP pacing flaw to cause memory/netns leaks, potentially leading to denial of service conditions through resource exhaustion on Linux-based systems and numerous NetApp appliances.

Affected Products

• Linux Kernel versions 4.18 to 4.19
• NetApp Active IQ Unified Manager for VMware vSphere
• NetApp Cloud Volumes ONTAP Mediator
• NetApp E-Series SANtricity OS Controller
• NetApp Element Software
• NetApp HCI Management Node
• NetApp SolidFire
• NetApp StorageGRID
• NetApp HCI Compute Node and Bootstrap OS
• NetApp H-Series Storage and Compute Nodes (H300S, H500S, H700S, H300E, H500E, H700E, H410S, H410C)

Discovery Timeline

• May 25, 2022 - CVE-2022-1678 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-1678

Vulnerability Analysis

This vulnerability resides in the Linux kernel's TCP output handling, specifically within the internal pacing mechanism implemented in net/ipv4/tcp_output.c. The TCP pacing feature is designed to regulate the rate at which TCP segments are transmitted to improve network performance and reduce congestion. However, an improper reference counting issue in the socket handling code causes memory resources to not be properly released after use.

When TCP pacing is active, the kernel maintains references to socket structures (struct sock) to track transmission timing. The vulnerability occurs because these references are not correctly decremented under certain conditions, leading to orphaned socket structures that persist in memory. Over time, repeated exploitation can cause significant memory consumption and network namespace leaks.

The flaw is classified under CWE-911 (Improper Update of Reference Count), which describes situations where reference counting mechanisms fail to properly track object lifecycles, resulting in resource leaks or use-after-free conditions.

Root Cause

The root cause of this vulnerability is an improper socket reference update in the TCP internal pacing code path. When the kernel processes TCP segments with pacing enabled, it must properly manage the lifecycle of socket references to ensure resources are released when no longer needed. The vulnerable code path failed to correctly update the reference count in certain scenarios, causing socket structures to remain allocated even after their intended use had completed.

This reference counting error affects the tcp_internal_pacing() function, where the struct tcp_sock pointer and timing variables (ktime_t expire, now) needed to be properly handled to prevent leaks.

Attack Vector

The attack vector is network-based and can be exploited remotely without requiring authentication or user interaction. An attacker can trigger this vulnerability by:

1. Establishing TCP connections to a vulnerable Linux server
2. Sending traffic patterns that activate the internal TCP pacing mechanism
3. Repeatedly exercising the vulnerable code path to accumulate memory leaks
4. Continuing until system resources are exhausted, causing denial of service

The vulnerability is particularly concerning in server environments handling numerous concurrent TCP connections, where the cumulative effect of memory leaks can quickly impact system stability.

// Security patch in net/ipv4/tcp_output.c - tcp: fix possible socket leaks in internal pacing mode
 
static void tcp_internal_pacing(struct sock *sk, const struct sk_buff *skb)
{
+	struct tcp_sock *tp = tcp_sk(sk);
+	ktime_t expire, now;
	u64 len_ns;
	u32 rate;

Source: GitHub Linux Commit

The patch introduces proper initialization of the tcp_sock pointer and timing variables at the beginning of the tcp_internal_pacing() function, ensuring correct reference handling throughout the pacing operation.

Detection Methods for CVE-2022-1678

Indicators of Compromise

• Unusual growth in kernel memory usage, particularly in TCP-related data structures
• Increasing count of orphaned network namespaces on the system
• Memory allocation warnings or out-of-memory conditions in kernel logs
• Degraded system performance under normal network load conditions

Detection Strategies

• Monitor kernel memory allocations using tools like /proc/meminfo and /proc/slabinfo for anomalous growth in TCP-related caches
• Implement network traffic analysis to identify patterns of connections that may be triggering the pacing code path
• Deploy kernel-level monitoring to track socket reference counts and detect potential leaks
• Review system logs for memory-related warnings such as sk_buff or socket allocation failures

Monitoring Recommendations

• Configure alerting on sustained memory usage growth that cannot be attributed to normal workload increases
• Track network namespace counts using ip netns list and alert on unexpected increases
• Monitor TCP connection statistics via /proc/net/tcp for unusual patterns
• Implement baseline memory metrics to enable rapid detection of resource leak conditions

How to Mitigate CVE-2022-1678

Immediate Actions Required

• Update the Linux kernel to a patched version that includes commit 0a70f118475e037732557796accd0878a00fc25a
• Apply vendor-specific patches from NetApp for affected storage and HCI products (see NetApp Security Advisory NTAP-20220715-0001)
• Implement network segmentation to limit exposure of vulnerable systems to untrusted networks
• Consider temporarily disabling TCP pacing if operationally feasible and the fix cannot be immediately applied

Patch Information

The vulnerability has been addressed in the upstream Linux kernel through commit 0a70f118475e037732557796accd0878a00fc25a. This patch fixes the socket leak issue by properly initializing the tcp_sock pointer and timing variables in the tcp_internal_pacing() function. Organizations should apply kernel updates from their distribution vendors that incorporate this fix.

For NetApp products, refer to the NetApp Security Advisory NTAP-20220715-0001 for specific firmware and software update guidance. Additional errata information is available through OpenAnolis Errata ANSA-2022:0143.

Workarounds

• Implement rate limiting on incoming TCP connections to reduce the frequency of pacing code path execution
• Configure firewall rules to restrict TCP connections to trusted sources only
• Deploy application-layer load balancers that can absorb connection load before it reaches vulnerable kernel code
• Monitor and restart systems if memory leak symptoms are detected before patches can be applied

# Configuration example - Monitor memory and namespace usage
# Check kernel memory usage for TCP-related structures
cat /proc/slabinfo | grep -E "(tcp|sock)"

# Monitor network namespace count
ip netns list 2>/dev/null | wc -l

# Check for memory pressure indicators
cat /proc/meminfo | grep -E "(MemFree|MemAvailable|Slab)"

# Review kernel logs for memory-related warnings
dmesg | grep -iE "(memory|alloc|oom|sock)"