CVE-2025-21869
📋 TL;DR
This CVE describes a Linux kernel vulnerability on PowerPC systems where KASAN (Kernel Address Sanitizer) incorrectly reports memory access violations during code patching operations. This occurs when using a temporary memory management structure for patching, causing false positive KASAN reports that could disrupt system operations. The vulnerability affects PowerPC systems running Linux kernel versions with specific code-patching implementations.
💻 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 →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 instability or crashes due to false KASAN reports disrupting legitimate kernel operations, potentially leading to denial of service conditions.
Likely Case
False positive KASAN reports causing system logs to fill with error messages, potentially masking real security issues and creating operational noise.
If Mitigated
Minimal impact - false reports are logged but system continues functioning normally with proper monitoring and alert filtering.
🎯 Exploit Status
Exploitation requires triggering specific kernel operations that use the vulnerable code-patching path, typically through BPF program loading or similar mechanisms.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits 5980d4456dd66d1b6505d5ec15048bd87e8775e0, dc9c5166c3cb044f8a001e397195242fd6796eee, or ea291447a4031f3dac5c23d55bc83fe833820d84
Vendor Advisory: https://git.kernel.org/stable/c/5980d4456dd66d1b6505d5ec15048bd87e8775e0
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fix commits. 2. For PowerPC systems: ensure you're using kernel 6.13+ with backported fixes or later stable versions. 3. Reboot system after kernel update.
🔧 Temporary Workarounds
Disable KASAN
PowerPC LinuxDisable Kernel Address Sanitizer to prevent false positive reports
Rebuild kernel with CONFIG_KASAN=n or boot with 'kasan=off' kernel parameter
Limit BPF operations
allRestrict BPF program loading to reduce triggering of vulnerable code path
sysctl -w kernel.unprivileged_bpf_disabled=1
Restrict BPF system calls via seccomp
🧯 If You Can't Patch
- Monitor system logs for KASAN reports and implement alert filtering to ignore known false positives
- Implement strict access controls to limit who can load BPF programs or perform kernel patching operations
🔍 How to Verify
Check if Vulnerable:
Check kernel version and KASAN configuration: 'uname -r' and verify if KASAN is enabled in /proc/config.gz or /boot/config-$(uname -r)Check Version:
uname -rVerify Fix Applied:
Verify kernel contains fix commits: 'grep -E "5980d4456dd66d1b6505d5ec15048bd87e8775e0|dc9c5166c3cb044f8a001e397195242fd6796eee|ea291447a4031f3dac5c23d55bc83fe833820d84" /proc/version' or check kernel source📡 Detection & Monitoring
Log Indicators:
- KASAN reports mentioning 'copy_to_kernel_nofault' or '__patch_instructions'
- System logs showing 'BUG: KASAN: user-memory-access' during BPF operations
Network Indicators:
- No specific network indicators - this is a local kernel issue
SIEM Query:
source="kernel" AND "KASAN: user-memory-access" AND ("copy_to_kernel_nofault" OR "__patch_instructions")