CVE-2023-53035 is a vulnerability identified in the Linux kernel's NILFS2 (New Implementation of a Log-structured File System) subsystem. The flaw exists in the ioctl helper function nilfs_ioctl_wrap_copy(), which is responsible for exchanging metadata arrays between kernel space and user space. Specifically, the vulnerability arises when the user-space metadata element size (v_size) provided in the nilfs_argv structure is larger than the corresponding metadata element size on the file system side (either nilfs_suinfo or nilfs_cpinfo structures). Under these conditions, the function may copy uninitialized kernel memory regions to user space during read-only ioctl commands NILFS_IOCTL_GET_SUINFO and NILFS_IOCTL_GET_CPINFO. This results in an information leak, exposing potentially sensitive kernel memory contents to unprivileged users. The issue was detected by Kernel Memory Sanitizer (KMSAN) instrumentation, which flagged kernel-infoleak errors during the copy_to_user operation. The root cause is that the allocated buffer page used for copying metadata was not zero-initialized, allowing residual uninitialized data to be copied out. The fix implemented involves initializing the allocated buffer page with get_zeroed_page(), ensuring no uninitialized kernel memory is leaked to user space. This vulnerability affects Linux kernel versions containing the specified commit hashes prior to the patch and is relevant to systems using the NILFS2 file system. No known exploits are reported in the wild as of the publication date. No CVSS score has been assigned to this vulnerability yet.

For European organizations, the impact of CVE-2023-53035 primarily concerns confidentiality risks due to kernel memory information leakage. Although this vulnerability does not directly allow privilege escalation or code execution, leaking kernel memory can expose sensitive data such as kernel pointers, internal kernel data structures, or other metadata that could aid attackers in crafting further attacks or bypassing security mechanisms like Kernel Address Space Layout Randomization (KASLR). Organizations running Linux servers or workstations with NILFS2 file systems are at risk. NILFS2 is less commonly used than other file systems like ext4 or XFS but is favored in some niche environments requiring continuous snapshotting and log-structured file system features. European enterprises in sectors such as research, telecommunications, or specialized storage infrastructures might employ NILFS2. The vulnerability requires local access to invoke the ioctl commands, so the threat surface is limited to users or processes with local system access. However, in multi-tenant or shared environments, this could allow unprivileged users to glean kernel memory contents, potentially facilitating privilege escalation or targeted attacks. The absence of known exploits reduces immediate risk, but the vulnerability's presence in the Linux kernel mandates timely patching to prevent information disclosure that could be leveraged in multi-stage attacks.

1. Apply the official Linux kernel patches that initialize the buffer with get_zeroed_page() as soon as they become available for your distribution or kernel version. 2. If immediate patching is not feasible, restrict local user access to systems running NILFS2 file systems to trusted personnel only, minimizing the risk of exploitation. 3. Monitor and audit usage of ioctl commands related to NILFS2, particularly NILFS_IOCTL_GET_SUINFO and NILFS_IOCTL_GET_CPINFO, to detect unusual or unauthorized invocations. 4. Consider disabling or avoiding the use of NILFS2 file systems on critical systems unless required, migrating data to more commonly used and actively maintained file systems with fewer known vulnerabilities. 5. Employ kernel hardening and memory protection mechanisms such as KASLR and Kernel Page Table Isolation (KPTI) to reduce the impact of potential information leaks. 6. Maintain up-to-date system monitoring and intrusion detection to identify suspicious local activity that could indicate attempts to exploit this or related vulnerabilities.