CVE-2022-50277
📋 TL;DR
A vulnerability in the Linux kernel's ext4 filesystem allows a NULL pointer dereference when mounting a filesystem with a journal inode marked for encryption and using the 'inlinecrypt' mount option. This causes a kernel crash (denial of service) affecting Linux systems using ext4 with encryption features. Attackers with local access can trigger this by mounting specially crafted filesystems.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic leading to system crash and denial of service, potentially requiring physical or remote console access to reboot.
Likely Case
Local denial of service through kernel crash when mounting malicious filesystems, requiring reboot to restore service.
If Mitigated
No impact if systems don't use ext4 encryption or inlinecrypt mount option, or if journal inodes aren't maliciously modified.
🎯 Exploit Status
Requires local access to mount filesystems and ability to modify journal inode flags. Not remotely exploitable. Proof of concept requires debugfs access and specific mount options.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel patches in stable trees: 105c78e12468413e426625831faa7db4284e1fec, 1f7a6626f611aa06d7907aa45b484708dd5ac8bc, bcc5057e1781a3ee889225480d995c3b5cbde555
Vendor Advisory: https://git.kernel.org/stable/c/105c78e12468413e426625831faa7db4284e1fec
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution. 2. Check kernel version with 'uname -r'. 3. Reboot system after kernel update. 4. Verify patch applied with 'dmesg | grep -i ext4' or check kernel source.
🔧 Temporary Workarounds
Avoid inlinecrypt mount option
allDo not use 'inlinecrypt' mount option for ext4 filesystems, especially with untrusted filesystems.
mount /dev/device /mountpoint (without -o inlinecrypt)
Remove 'inlinecrypt' from /etc/fstab entries
Restrict debugfs access
allLimit access to debugfs utility that can modify inode flags.
chmod 700 /sbin/debugfs
setfacl or sudoers restrictions on debugfs
🧯 If You Can't Patch
- Avoid mounting untrusted ext4 filesystems, especially with inlinecrypt option
- Implement strict access controls on filesystem mounting operations and debugfs utility
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if ext4 with encryption is used: 'uname -r', 'mount | grep ext4', check for inlinecrypt in mount options.Check Version:
uname -rVerify Fix Applied:
Verify kernel version is patched: check if commit 105c78e12468413e426625831faa7db4284e1fec or related patches are in kernel source. Test mount with inlinecrypt on test filesystem.📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages in /var/log/messages or dmesg
- NULL pointer dereference errors mentioning fscrypt_limit_io_blocks() or ext4_iomap_begin()
- System crash/reboot logs after mount operations
Network Indicators:
- None - local exploit only
SIEM Query:
source="kernel" AND ("NULL pointer dereference" OR "fscrypt_limit_io_blocks" OR "ext4_iomap_begin")