CVE-2023-53391 in Linux
Summary
by MITRE • 09/18/2025
In the Linux kernel, the following vulnerability has been resolved:
shmem: use ramfs_kill_sb() for kill_sb method of ramfs-based tmpfs
As the ramfs-based tmpfs uses ramfs_init_fs_context() for the init_fs_context method, which allocates fc->s_fs_info, use ramfs_kill_sb() to free it and avoid a memory leak.
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Analysis
by VulDB Data Team • 12/13/2025
The vulnerability identified as CVE-2023-53391 resides within the Linux kernel's memory management subsystem, specifically affecting the shared memory implementation through tmpfs filesystem operations. This issue demonstrates a classic memory leak scenario that occurs during filesystem cleanup operations, where improper resource deallocation leads to persistent memory consumption. The vulnerability affects systems utilizing tmpfs filesystems that are based on ramfs implementation, which serves as a fundamental component for temporary file storage in Linux environments.
The technical flaw manifests in the inconsistent handling of filesystem context cleanup between the initialization and destruction phases of tmpfs filesystem operations. When tmpfs initializes its filesystem context using ramfs_init_fs_context(), it allocates memory structures within the filesystem context's s_fs_info field. However, during the kill_sb operation, the system fails to utilize the appropriate ramfs_kill_sb() function that would properly free these allocated resources. This discrepancy creates a memory leak where the allocated fc->s_fs_info memory remains unreleased even after the filesystem is unmounted or destroyed.
The operational impact of this vulnerability extends beyond simple memory consumption issues to potentially affect system stability and performance over extended periods of operation. While individual memory leaks may appear minor, cumulative effects across multiple filesystem operations or prolonged system uptime can lead to significant memory pressure. This vulnerability particularly affects systems that frequently mount and unmount tmpfs filesystems, or those running applications that heavily utilize temporary file storage mechanisms. The memory leak can contribute to system degradation and may eventually lead to memory exhaustion under high load conditions.
The vulnerability aligns with CWE-401, which specifically addresses improper resource deallocation, and represents a classic example of memory management failure in kernel space. From an ATT&CK perspective, this issue falls under the category of privilege escalation and system stability degradation, as it can be exploited to consume system resources and potentially contribute to denial of service conditions. The fix implemented addresses this by ensuring that ramfs_kill_sb() is used consistently for kill_sb operations, which properly handles the deallocation of fc->s_fs_info structures that were allocated during initialization.
Mitigation strategies for this vulnerability include immediate kernel updates to versions containing the patched implementation, which ensures proper memory management through consistent use of ramfs_kill_sb() for filesystem cleanup operations. System administrators should prioritize patching this vulnerability, particularly on systems with high tmpfs usage or those operating in memory-constrained environments. Additionally, monitoring memory usage patterns and filesystem operations can help detect potential impacts from this vulnerability before they escalate to system stability issues. The fix demonstrates the importance of maintaining consistency in kernel memory management practices and highlights the critical nature of proper resource deallocation in operating system components.