How CVE-2025-37925 Works
The vulnerability occurs in the JFS filesystem implementation within the Linux kernel when processing on-disk inodes. According to JFS specifications, inode types 5-15 are reserved for future use and should never appear on valid filesystems. The flaw allows specially crafted inodes of unsupported types (5-15) to bypass validation checks during filesystem operations. When such invalid inodes are processed, the kernel attempts to execute unsupported operations through the clear_inode() function, triggering a kernel BUG() and causing a system crash (denial of service). The issue stems from missing type validation in copy_from_dinode() before processing inode metadata.
DailyCVE Form
Platform: Linux Kernel
Version: Pre-6.12.0-rc4
Vulnerability: Inode Type Validation
Severity: Critical
Date: 04/18/2025
What Undercode Say:
Analytics:
- Attack Vector: Local/Remote (depending on filesystem access)
- Complexity: Low (single malformed inode triggers crash)
- Privileges Required: User-level (filesystem write access)
- Impact: DoS (kernel panic)
Exploit Commands:
Craft malicious JFS filesystem image dd if=/dev/zero of=malicious.img bs=1M count=100 mkfs.jfs -i 7 malicious.img Using reserved inode type mount -o loop malicious.img /mnt/exploit
Protection Commands:
Immediate mitigation echo "blacklist jfs" >> /etc/modprobe.d/blacklist.conf Patch verification grep -r "copy_from_dinode" /usr/src/linux/fs/jfs Runtime monitoring auditctl -w /usr/bin/mount -p x -k jfs_mount
Code Snippets:
// Vulnerable code path (simplified)
void clear_inode(struct inode inode) {
if (inode->i_type > 15) // Missing check
BUG();
// ... rest of cleanup
}
// Patch verification
int copy_from_dinode(struct dinode dip, struct inode ip) {
if (dip->di_type < 1 || dip->di_type > 4) // Should be present
return -EINVAL;
// ... copy operations
}
Detection Script:
!/usr/bin/python3
import os
def check_jfs_mounts():
with open('/proc/mounts') as f:
return any('jfs' in line for line in f)
if check_jfs_mounts():
print("WARNING: JFS filesystem mounted")
Kernel Config Protection:
Disable JFS at compile time CONFIG_JFS_FS=n
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
