CVE-2021-47632
📋 TL;DR
This CVE describes a spinlock recursion vulnerability in the Linux kernel's powerpc/set_memory module. The issue occurs in change_page_attr() function when performing memory permission changes, potentially causing kernel panics or system crashes. It affects Linux systems running on PowerPC architecture with specific kernel versions.
💻 Affected Systems
- Linux Kernel
📦 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
Kernel panic leading to system crash and denial of service, potentially causing data loss or system instability.
Likely Case
System crash or kernel panic when memory management operations trigger the spinlock recursion, resulting in denial of service.
If Mitigated
Minor performance impact or no impact if the vulnerable code path isn't triggered during normal operations.
🎯 Exploit Status
Exploitation requires triggering specific kernel memory operations, likely requiring local access and specific conditions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in kernel commits: 6def4eaf0391f24be541633a954c0e4876858b1e, 6ebe5ca2cbe438a688f2ae238ef5a0b0b5f3468a, 96917107e67846f1d959ed03be281048efad14c5, a4c182ecf33584b9b2d1aa9dad073014a504c01f
Vendor Advisory: https://git.kernel.org/stable/c/6def4eaf0391f24be541633a954c0e4876858b1e
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fix commits. 2. For distributions: Apply security updates from your vendor. 3. Reboot system to load new kernel.
🔧 Temporary Workarounds
Avoid triggering memory operations
linuxLimit processes that perform extensive memory management operations on PowerPC systems
🧯 If You Can't Patch
- Monitor system logs for spinlock recursion errors and restart affected systems
- Limit user access to systems and restrict memory-intensive operations
🔍 How to Verify
Check if Vulnerable:
Check kernel version and architecture: uname -a should show PowerPC architecture and vulnerable kernel version rangeCheck Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits or check with distribution's security update status📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages mentioning spinlock recursion
- BUG: spinlock recursion on CPU# messages in dmesg or system logs
- Call traces showing change_page_attr() in stack
SIEM Query:
source="kernel" AND "spinlock recursion" AND "change_page_attr"