CVE-2025-37870 in Linux
Summary
by MITRE • 05/09/2025
In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: prevent hang on link training fail
[Why]
When link training fails, the phy clock will be disabled. However, in enable_streams, it is assumed that link training succeeded and the mux selects the phy clock, causing a hang when a register write is made.
[How]
When enable_stream is hit, check if link training failed. If it did, fall back to the ref clock to avoid a hang and keep the system in a recoverable state.
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Analysis
by VulDB Data Team • 01/31/2026
The vulnerability identified as CVE-2025-37870 resides within the Linux kernel's graphics subsystem, specifically within the amd display driver component under the direct render manager framework. This issue manifests as a system hang during display initialization processes, representing a critical reliability concern that can disrupt normal system operation. The vulnerability occurs in the drm/amd/display subsystem where the driver manages display output connections and link training procedures for AMD graphics hardware. When the system encounters a failure during the link training phase of display communication, the driver's state management becomes inconsistent, leading to a complete system hang that prevents further operation.
The technical flaw stems from improper state handling during the display stream enablement process. During link training failures, the driver correctly disables the phy clock as a safety measure, but the enable_streams function does not properly account for this failure condition. The code assumes that link training has succeeded and proceeds to configure the mux to select the phy clock, creating a logical inconsistency. This design flaw creates a scenario where the system attempts to write to registers using a disabled clock source, resulting in an unrecoverable hang state. The issue demonstrates poor error handling and state validation within the display driver's initialization sequence.
The operational impact of this vulnerability extends beyond simple system hangs, potentially affecting system availability and user experience in environments where display output is critical. When the system encounters a link training failure, particularly in scenarios involving external displays or complex display configurations, the entire system may become unresponsive, requiring manual intervention or power cycling. This vulnerability affects systems running Linux kernels with AMD graphics hardware where display link training may fail due to various factors including cable issues, incompatible display modes, or hardware limitations. The hang condition prevents normal system operation and can lead to data loss or service interruption in production environments.
Mitigation strategies for this vulnerability focus on implementing proper error checking and fallback mechanisms within the display driver code. The recommended solution involves modifying the enable_stream function to check for link training failure conditions before attempting to configure the mux selection. When link training fails, the driver should fall back to using the reference clock instead of attempting to use the disabled phy clock. This approach aligns with defensive programming principles and ensures system recoverability. The fix should be implemented following established security practices and kernel development guidelines, ensuring that all error conditions are properly handled without compromising system stability. This vulnerability would typically be classified under CWE-399 as "Resource Management Errors" and could potentially be leveraged in denial-of-service scenarios according to ATT&CK technique T1499.100.
The resolution of this vulnerability requires careful attention to the driver's state management and error recovery mechanisms, ensuring that all hardware initialization sequences properly validate their conditions before proceeding with critical operations. System administrators should ensure that kernel updates incorporating this fix are applied promptly to prevent potential system hangs in environments utilizing AMD graphics hardware. The fix demonstrates the importance of comprehensive error handling in kernel drivers and highlights the need for robust state validation in complex hardware interaction scenarios.