CVE-2022-49912 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix ulist leaks in error paths of qgroup self tests
In the test_no_shared_qgroup() and test_multiple_refs() qgroup self tests, if we fail to add the tree ref, remove the extent item or remove the extent ref, we are returning from the test function without freeing the "old_roots" ulist that was allocated by the previous calls to btrfs_find_all_roots(). Fix that by calling ulist_free() before returning.
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Analysis
by VulDB Data Team • 11/12/2025
The vulnerability identified as CVE-2022-49912 resides within the Linux kernel's btrfs file system implementation, specifically affecting the qgroup self-test functionality. This issue represents a memory management flaw that occurs during error handling paths within the kernel's test suite rather than in production code execution. The btrfs file system employs qgroups to track quota information for subvolumes, making this vulnerability particularly significant for systems relying on advanced storage management features. The flaw manifests when testing scenarios involving qgroup operations, specifically during the test_no_shared_qgroup() and test_multiple_refs() functions where memory allocation occurs but subsequent deallocation fails under error conditions.
The technical root cause of this vulnerability stems from improper resource cleanup in error handling paths of the btrfs kernel module. When the test functions encounter failures while attempting to add tree references, remove extent items, or remove extent references, they prematurely return from the function without properly freeing previously allocated memory structures. The "old_roots" ulist structure, which is allocated by calls to btrfs_find_all_roots(), becomes a memory leak when the function exits early due to error conditions. This represents a classic memory leak vulnerability classified under CWE-401: Improper Release of Memory Before Removing Last Reference, where allocated memory resources are not properly deallocated during exceptional program flow.
The operational impact of this vulnerability extends beyond simple memory consumption issues, as it demonstrates a fundamental flaw in the kernel's error handling mechanisms for test functions. While the vulnerability primarily affects the kernel's self-testing infrastructure rather than production file system operations, it reflects poor memory management practices that could potentially be replicated in other kernel subsystems. The memory leaks accumulate during test execution, which could lead to system performance degradation over time, particularly in environments running extensive kernel testing procedures or automated test suites. This vulnerability affects systems using btrfs file systems that execute these specific qgroup self-tests, potentially impacting developers and system administrators working with kernel development or testing environments.
Mitigation strategies for this vulnerability focus on ensuring proper resource cleanup in error handling paths. The fix implemented in the kernel addresses the issue by adding explicit ulist_free() calls before returning from the test functions when errors occur. This approach aligns with best practices for memory management in kernel space programming and follows the principle of ensuring that all allocated resources are properly released regardless of execution path. System administrators should ensure their kernels are updated to versions containing this fix, particularly those running development environments or automated testing frameworks that may exercise these specific qgroup test functions. The vulnerability also serves as a reminder for kernel developers to rigorously test error handling paths and ensure proper resource cleanup in all code paths, including exceptional conditions that may occur during complex file system operations.