CVE-2021-47513
📋 TL;DR
A memory leak vulnerability exists in the Linux kernel's DSA (Distributed Switch Architecture) Felix driver. If a system using this driver lacks a defined CPU port, the felix_setup_mmio_filtering function fails to properly free allocated memory, leading to gradual resource exhaustion. This affects Linux systems with specific network hardware configurations using the DSA Felix driver.
💻 Affected Systems
- Linux kernel with DSA Felix driver
📦 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 →⚠️ Risk & Real-World Impact
Worst Case
Sustained exploitation could cause kernel memory exhaustion, leading to system instability, crashes, or denial of service on affected network devices.
Likely Case
Gradual memory consumption over time, potentially causing performance degradation or system instability in affected configurations.
If Mitigated
Minimal impact with proper monitoring and memory management controls in place.
🎯 Exploit Status
Exploitation requires specific hardware configuration and kernel access. Memory leak vulnerabilities are typically not weaponized for remote attacks.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel commits 973a0373e88cc19129bd6ef0ec193040535397d9 and e8b1d7698038e76363859fb47ae0a262080646f5
Vendor Advisory: https://git.kernel.org/stable/c/973a0373e88cc19129bd6ef0ec193040535397d9
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fix. 2. Check distribution-specific security advisories. 3. Reboot system after kernel update.
🔧 Temporary Workarounds
Ensure CPU port configuration
linuxConfigure DSA Felix driver with proper CPU port definition to avoid triggering the vulnerable code path
# Check DSA configuration in device tree or kernel parameters
# Ensure CPU port is properly defined for Felix driver
🧯 If You Can't Patch
- Monitor system memory usage for unusual consumption patterns
- Restrict access to systems using DSA Felix driver configuration
🔍 How to Verify
Check if Vulnerable:
Check kernel version and DSA Felix driver configuration. Vulnerable if using affected kernel with DSA Felix driver without CPU port.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits or check with distribution security updates.📡 Detection & Monitoring
Log Indicators:
- Kernel oom-killer messages
- Memory allocation failures
- System instability logs
Network Indicators:
- Degraded network performance on affected interfaces
SIEM Query:
Search for kernel panic, oom-killer, or memory exhaustion events on systems with DSA Felix driver