Linux Kernel Uninitialized Variable Vulnerability in File Attribute Handling

A vulnerability has been identified in the Linux kernel related to uninitialized variable handling in the file attribute management system. This issue occurs in the stable branch of the Linux kernel. The problem arises because the internal 'file_kattr' structure is not properly initialized before being used, which can lead to the use of undefined values. The vulnerability was reported by syzbot, highlighting that the 'flags_valid' field of the 'file_kattr' structure should be set to true before calling the 'vfs_fileattr_get' function. This oversight can cause inconsistencies in file attribute retrieval, potentially leading to unexpected behavior in file management operations.

Impact

Exploitation of this vulnerability can cause undefined behavior in the file attribute management system, potentially leading to incorrect file handling or attribute retrieval.

Reproduction

The vulnerability can be reproduced by invoking the 'file_getattr' system call without properly initializing the 'file_kattr' structure. This can be done by creating a local variable of type 'file_kattr' and leaving it uninitialized, then passing it to the 'vfs_fileattr_get' function. The kernel's KMSAN (Kernel Memory Sanitizer) will detect the use of the uninitialized variable, indicating the presence of the vulnerability.

Remediation

Users can upgrade to the latest version of the Linux kernel where this vulnerability has been addressed. The specific commit that resolves this issue is available in the Linux kernel stable tree.