CVE-2022-49644 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
drm/i915: fix a possible refcount leak in intel_dp_add_mst_connector()
If drm_connector_init fails, intel_connector_free will be called to take care of proper free. So it is necessary to drop the refcount of port before intel_connector_free.
(cherry picked from commit cea9ed611e85d36a05db52b6457bf584b7d969e2)
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Analysis
by VulDB Data Team • 02/26/2025
The vulnerability identified as CVE-2022-49644 resides within the Linux kernel's graphics subsystem, specifically affecting the intel i915 driver responsible for handling display output on intel graphics hardware. This issue manifests in the drm/i915 subsystem where improper reference counting management can lead to resource leaks during connector initialization failures. The flaw occurs in the intel_dp_add_mst_connector() function which handles multi-stream transport connections for intel graphics devices. When the drm_connector_init function fails during the initialization process, the system attempts to clean up resources through intel_connector_free, but the reference count of the port object is not properly decremented before this cleanup occurs. This oversight creates a potential refcount leak that can accumulate over time and eventually lead to resource exhaustion.
The technical implementation of this vulnerability stems from a missing reference count decrement operation in the error handling path of the intel_dp_add_mst_connector function. When drm_connector_init fails, the code path should ensure all acquired references are properly released before calling intel_connector_free to perform the final cleanup. However, the port reference count is not dropped before the cleanup function executes, resulting in a reference count that remains elevated beyond its intended lifetime. This violates fundamental resource management principles and creates a condition where the kernel's memory management system cannot properly reclaim the port object, leading to potential memory leaks that can grow over time with repeated failures. The vulnerability specifically relates to improper handling of reference counting in kernel space, which is a common class of issues that can lead to system instability and resource exhaustion.
The operational impact of CVE-2022-49644 extends beyond simple memory consumption issues, as it can affect system stability and performance in graphics-intensive environments. While the immediate effect may appear as a minor resource leak, repeated occurrences can lead to progressive memory consumption that eventually impacts system responsiveness and overall performance. The vulnerability is particularly concerning in server environments or systems with continuous graphics processing where multiple connector initialization attempts might occur. The leak could potentially be exploited to cause denial of service conditions where system resources become exhausted, though the direct attack surface is limited to kernel-level graphics operations. Systems utilizing intel graphics hardware with multi-stream transport capabilities are most affected, particularly those running applications that frequently establish and tear down display connections.
Mitigation strategies for CVE-2022-49644 focus on applying the upstream patch that ensures proper reference count management before calling intel_connector_free. The fix involves adding a reference count decrement operation for the port object immediately before the cleanup function execution in the error handling path. This approach aligns with established kernel development practices for resource management and follows the principle of releasing all acquired resources before function exit. System administrators should prioritize applying the kernel update containing this fix, particularly in production environments where graphics stability is critical. The vulnerability does not require special privileges to trigger, making it a concern for all users of affected systems. Monitoring for unusual memory consumption patterns in graphics-related processes may help identify systems that have been affected by this leak before it causes noticeable performance degradation. This fix represents a standard defensive programming technique that prevents resource leaks and aligns with security best practices for kernel development, addressing a specific weakness in the reference counting mechanism that could lead to resource exhaustion.
This vulnerability relates to CWE-404, which describes improper resource management, and specifically addresses improper reference counting that can lead to resource leaks. The issue demonstrates the importance of proper resource management in kernel space operations and aligns with ATT&CK technique T1499.001 for resource exhaustion attacks, though the vulnerability itself is more accurately classified as a resource management flaw rather than an active attack vector. The fix represents a defensive programming approach that ensures all acquired references are properly released, which is a fundamental requirement for maintaining system stability and preventing resource exhaustion attacks that could be leveraged by malicious actors to cause denial of service conditions.