CVE-2022-49915 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
mISDN: fix possible memory leak in mISDN_register_device()
Afer commit 1fa5ae857bb1 ("driver core: get rid of struct device's bus_id string array"), the name of device is allocated dynamically, add put_device() to give up the reference, so that the name can be freed in kobject_cleanup() when the refcount is 0.
Set device class before put_device() to avoid null release() function WARN message in device_release().
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Analysis
by VulDB Data Team • 07/11/2025
The vulnerability CVE-2022-49915 addresses a memory leak in the Linux kernel's mISDN subsystem that emerged following a significant refactor of the device core subsystem. This issue specifically affects the mISDN_register_device() function within the mISDN driver framework, which handles the registration of ISDN (Integrated Services Digital Network) devices. The root cause stems from changes made in commit 1fa5ae857bb1 that eliminated the static bus_id string array from the struct device structure, replacing it with dynamically allocated memory management. This architectural change necessitated proper reference counting and memory cleanup procedures to prevent resource leaks when device objects are destroyed.
The technical flaw manifests when device registration fails or when the device cleanup process does not properly release the dynamically allocated name string. In the previous implementation, the device name was statically allocated and managed automatically, but the new dynamic allocation approach requires explicit reference management through proper use of put_device() calls. When put_device() is invoked without first setting the device class, the kernel's device release mechanism generates warning messages about a null release function, indicating improper device state management. This improper sequence can lead to memory that should be freed remaining allocated, creating a memory leak that accumulates over time and potentially impacts system stability and performance.
The operational impact of this vulnerability extends beyond simple memory consumption issues, as it represents a potential denial of service vector that could degrade system performance or cause unexpected behavior in telephony and communication applications relying on mISDN functionality. Systems running Linux kernels with affected versions may experience progressive memory degradation, particularly in environments with frequent device registration and deregistration cycles. The vulnerability affects any system utilizing the mISDN subsystem for ISDN device management, including enterprise communication systems, telephony gateways, and embedded devices that require digital telephone line connectivity.
Mitigation strategies for CVE-2022-49915 involve applying the kernel patch that corrects the device registration sequence by ensuring device class is set before calling put_device(), thereby preventing the memory leak and associated warning messages. System administrators should prioritize updating to kernel versions containing the fix, typically found in kernel releases 5.19 and later. The fix aligns with best practices for device management in the Linux kernel and addresses a fundamental issue in resource cleanup that could have broader implications for other drivers using similar patterns. This vulnerability demonstrates the importance of proper reference counting and resource management in kernel subsystems, particularly when architectural changes modify memory allocation patterns. The solution reflects adherence to proper kernel development practices and follows established guidelines for device core management, ensuring that device objects are properly cleaned up and memory is appropriately released when device references reach zero. This remediation addresses the underlying CWE-404 issue of improper resource management and helps prevent potential exploitation scenarios that could leverage memory leaks for system instability or performance degradation.