CVE-2021-47640
📋 TL;DR
A memory corruption vulnerability in the Linux kernel's KASAN (Kernel Address SANitizer) subsystem on PowerPC architecture causes incorrect shadow page table updates, leading to both false positive and false negative memory access detections. This affects Linux systems running on PowerPC hardware with specific page size configurations. Attackers could potentially bypass KASAN protections to execute memory corruption attacks.
💻 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
Kernel memory corruption leading to privilege escalation, denial of service, or arbitrary code execution by bypassing KASAN protections
Likely Case
System instability, crashes, or false security alerts due to incorrect memory access detection
If Mitigated
Reduced KASAN effectiveness but limited direct exploitation without additional vulnerabilities
🎯 Exploit Status
Requires local access and knowledge of PowerPC memory layout. Primarily a KASAN bypass rather than direct exploitation vector.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in kernel commits: 5a3d8f3192a4, 7f19245c3647, dd75080aa840, de56beace664, e3d157a4b4f4
Vendor Advisory: https://git.kernel.org/stable/c/5a3d8f3192a409893c57808cc935e16484df1068
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version. 2. For PowerPC systems: Apply kernel patches from stable branches. 3. Recompile kernel if using custom build. 4. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable KASAN
PowerPC LinuxDisable Kernel Address SANitizer feature to prevent incorrect memory access detection
Rebuild kernel with CONFIG_KASAN=n
🧯 If You Can't Patch
- Restrict local user access to PowerPC systems
- Monitor for kernel panic logs and unusual memory access patterns
🔍 How to Verify
Check if Vulnerable:
Check kernel version and architecture: uname -r and uname -m. If PowerPC and kernel version is before fixes, system may be vulnerable.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes fix commits: grep -q '5a3d8f3192a4\|7f19245c3647\|dd75080aa840\|de56beace664\|e3d157a4b4f4' /proc/version📡 Detection & Monitoring
Log Indicators:
- KASAN: vmalloc-out-of-bounds warnings
- Kernel panic logs
- False positive memory corruption alerts
Network Indicators:
- None - local vulnerability only
SIEM Query:
source="kernel" AND ("KASAN" OR "vmalloc-out-of-bounds" OR "kernel panic")🔗 References
- https://git.kernel.org/stable/c/5a3d8f3192a409893c57808cc935e16484df1068
- https://git.kernel.org/stable/c/7f19245c3647afea8c7c41f795506ef70f64b9f2
- https://git.kernel.org/stable/c/dd75080aa8409ce10d50fb58981c6b59bf8707d3
- https://git.kernel.org/stable/c/de56beace6648065d404cd9835aa7d30e3df519d
- https://git.kernel.org/stable/c/e3d157a4b4f4e0268c98be5b7013bf4b31234bb6
- https://git.kernel.org/stable/c/f39a3309393a4a484532f6ba745c6acbcfe06115
