CVE-2023-54062 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
ext4: fix invalid free tracking in ext4_xattr_move_to_block()
In ext4_xattr_move_to_block(), the value of the extended attribute which we need to move to an external block may be allocated by kvmalloc() if the value is stored in an external inode. So at the end of the function the code tried to check if this was the case by testing entry->e_value_inum.
However, at this point, the pointer to the xattr entry is no longer valid, because it was removed from the original location where it had been stored. So we could end up calling kvfree() on a pointer which was not allocated by kvmalloc(); or we could also potentially leak memory by not freeing the buffer when it should be freed. Fix this by storing whether it should be freed in a separate variable.
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Analysis
by VulDB Data Team • 12/30/2025
The vulnerability identified as CVE-2023-54062 represents a critical memory management flaw within the Linux kernel's ext4 filesystem implementation. This issue manifests in the ext4_xattr_move_to_block() function where improper handling of extended attribute memory allocation leads to potential memory corruption and resource leaks. The flaw occurs during the process of moving extended attributes from internal to external storage locations within the filesystem, specifically when dealing with attributes that have been allocated using the kvmalloc() memory allocator.
The technical root cause stems from a race condition in pointer validation logic within the ext4 filesystem driver. When processing extended attributes that need to be moved to external blocks, the code attempts to determine if the attribute value was allocated via kvmalloc() by checking the entry->e_value_inum field. However, this validation occurs after the xattr entry has already been removed from its original storage location, rendering the pointer invalid and causing unpredictable behavior. This invalid pointer dereference creates a scenario where kvfree() may be called on memory that was not allocated through the kvmalloc() pathway, or conversely, memory that should be freed remains allocated, leading to memory leaks.
The operational impact of this vulnerability extends beyond simple memory management issues to potentially compromise system stability and security. An attacker could exploit this flaw to cause system crashes through memory corruption or to facilitate memory exhaustion attacks that could lead to denial of service conditions. The vulnerability particularly affects systems running Linux kernels with ext4 filesystems where extended attributes are actively used, making it relevant to a broad range of computing environments including servers, desktop systems, and embedded devices. The flaw demonstrates poor memory management practices that violate established security principles and could enable privilege escalation or information disclosure attacks depending on the exploitation context.
The fix for CVE-2023-54062 involves implementing proper state tracking by storing the allocation status information in a separate variable before the xattr entry is removed from its original location. This approach prevents the invalid pointer dereference that leads to incorrect memory deallocation decisions. The solution aligns with security best practices for kernel memory management and follows the principle of least privilege by ensuring proper resource cleanup. This vulnerability is classified as a memory safety issue and maps to CWE-415, which covers double free conditions, and CWE-416, which addresses use after free conditions. From an ATT&CK perspective, this vulnerability could be leveraged for privilege escalation through kernel memory corruption techniques, potentially enabling lateral movement or persistence mechanisms within compromised systems. The fix ensures that memory management decisions are made based on valid state information rather than potentially stale pointers, thereby maintaining the integrity of the kernel's memory subsystem and preventing both memory corruption and resource leakage scenarios.