CVE-2022-50083 in Linux
Summary
by MITRE • 06/18/2025
In the Linux kernel, the following vulnerability has been resolved:
ext4: add EXT4_INODE_HAS_XATTR_SPACE macro in xattr.h
When adding an xattr to an inode, we must ensure that the inode_size is not less than EXT4_GOOD_OLD_INODE_SIZE + extra_isize + pad. Otherwise, the end position may be greater than the start position, resulting in UAF.
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Analysis
by VulDB Data Team • 11/30/2025
The vulnerability in question affects the ext4 filesystem implementation within the Linux kernel and represents a critical memory safety issue that could potentially lead to arbitrary code execution. This flaw specifically manifests during the process of adding extended attributes to inodes, where inadequate validation of inode size parameters creates conditions for heap-based use-after-free vulnerabilities. The issue stems from insufficient boundary checking when calculating the required space for extended attributes within inode structures.
The technical root cause involves the improper handling of inode size calculations during extended attribute operations. When an extended attribute is added to an inode, the system must verify that the inode_size field contains sufficient space to accommodate not only the basic inode structure but also the additional extended attribute space plus padding requirements. The vulnerability occurs because the code fails to validate that inode_size meets the minimum requirements of EXT4_GOOD_OLD_INODE_SIZE plus extra_isize plus pad before proceeding with the extended attribute addition process. This validation gap allows for scenarios where the calculated end position of the extended attribute storage exceeds the start position, creating a dangerous memory layout condition.
The operational impact of this vulnerability extends beyond simple memory corruption as it provides potential attack vectors for privilege escalation and system compromise. An attacker who can manipulate extended attribute operations on filesystem inodes could trigger the use-after-free condition through carefully crafted file operations or filesystem metadata modifications. The vulnerability affects any Linux system running ext4 filesystems where extended attributes are utilized, making it particularly concerning given the widespread adoption of ext4 as the default filesystem for numerous distributions and applications.
The fix implemented involves adding the EXT4_INODE_HAS_XATTR_SPACE macro to the xattr.h header file, which provides proper validation checks before extended attribute operations proceed. This macro ensures that inode size parameters meet minimum requirements before allowing extended attribute addition, effectively preventing the dangerous memory layout conditions that lead to use-after-free scenarios. The solution aligns with common security practices for preventing heap corruption vulnerabilities and follows established patterns for validating filesystem metadata structures.
This vulnerability maps directly to CWE-416, which covers Use After Free conditions in software systems. It also relates to ATT&CK technique T1059.007 for command and scripting interpreter, as the exploitation could enable attackers to execute arbitrary code through compromised system processes. The fix addresses fundamental filesystem integrity concerns that align with security frameworks emphasizing proper input validation and memory safety mechanisms. The resolution demonstrates the importance of comprehensive validation in kernel-level filesystem operations and highlights how seemingly minor parameter checking can prevent serious security vulnerabilities.
The mitigation strategy involves applying the kernel patch that introduces the extended validation macro, ensuring all ext4 filesystem implementations properly validate inode size requirements before extended attribute operations. System administrators should prioritize updating their kernel versions to include this fix, as the vulnerability exists in the core filesystem layer and affects all systems using ext4 filesystems with extended attributes enabled. Regular security updates and proper kernel maintenance are essential for protecting against similar issues that could arise from inadequate validation of filesystem metadata structures.