CVE-2022-48747 in Linux
Summary
by MITRE • 06/20/2024
In the Linux kernel, the following vulnerability has been resolved:
block: Fix wrong offset in bio_truncate()
bio_truncate() clears the buffer outside of last block of bdev, however current bio_truncate() is using the wrong offset of page. So it can return the uninitialized data.
This happened when both of truncated/corrupted FS and userspace (via bdev) are trying to read the last of bdev.
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Analysis
by VulDB Data Team • 05/21/2025
The vulnerability identified as CVE-2022-48747 resides within the Linux kernel's block layer implementation, specifically affecting the bio_truncate() function that handles bio (block I/O) operations. This flaw represents a critical security issue that can lead to information disclosure through the exposure of uninitialized memory contents. The vulnerability manifests when the kernel attempts to truncate bio operations that extend beyond the boundaries of a block device, particularly when dealing with filesystem operations that involve the final blocks of a device. The issue is classified under CWE-248, which deals with exposure of uninitialized variables, and impacts the fundamental integrity of data handling within the kernel's storage subsystem. When filesystem operations and user-space applications simultaneously attempt to access the final blocks of a block device, the improper handling of buffer offsets creates a condition where uninitialized memory may be returned to userspace applications.
The technical flaw occurs in the bio_truncate() function where the kernel incorrectly calculates the page offset when clearing buffer contents beyond the last block of a block device. This miscalculation results in the function not properly clearing memory that should be zeroed out, leaving uninitialized data accessible to applications. The vulnerability is particularly concerning because it operates at the kernel level where memory management and I/O operations are critical for system security and stability. When filesystems and user-space processes both attempt to read from the final portion of a block device simultaneously, the improper offset calculation causes the kernel to return uninitialized memory contents rather than properly cleared buffers. This behavior violates fundamental security principles by exposing potentially sensitive data that may contain remnants of previous operations, passwords, cryptographic keys, or other confidential information that was previously stored in the cleared memory regions.
The operational impact of CVE-2022-48747 extends beyond simple information disclosure to potentially enable more sophisticated attacks that could leverage the uninitialized data for privilege escalation or system compromise. Attackers could exploit this vulnerability by crafting specific I/O operations that trigger the flawed bio_truncate() function, particularly when dealing with filesystem operations that involve the final blocks of storage devices. The vulnerability affects systems running Linux kernel versions where the fix has not been applied, creating potential attack vectors for malicious actors who can monitor and manipulate I/O operations on block devices. This flaw particularly impacts storage-intensive applications and systems where filesystem operations are frequent, as the probability of triggering the condition increases with the frequency of I/O operations on block devices. The vulnerability also intersects with ATT&CK technique T1550.001, which involves unauthorized access to system resources through manipulation of I/O operations, and represents a direct threat to the confidentiality and integrity of data stored on affected systems.
Mitigation strategies for CVE-2022-48747 primarily focus on applying the appropriate kernel security patches that correct the bio_truncate() function's offset calculation logic. System administrators should prioritize updating their Linux kernel installations to versions that include the fix, which typically involves correcting the buffer offset calculation to properly clear all memory regions beyond the last valid block of the device. Organizations should implement comprehensive patch management processes to ensure all systems are updated promptly, as this vulnerability can be exploited by attackers with minimal privileges to access uninitialized memory contents. Additionally, monitoring systems should be configured to detect unusual I/O patterns that might indicate exploitation attempts, particularly around the final blocks of storage devices. The fix addresses the root cause by ensuring that when bio_truncate() operates on bio structures, it correctly calculates page offsets to guarantee that all buffer contents beyond the valid data range are properly cleared, preventing the leakage of uninitialized memory contents to user-space applications. This remediation aligns with security best practices for kernel-level vulnerability management and ensures proper memory handling within the Linux block layer.