CVE-2023-52485 in Linux
Summary
by MITRE • 02/29/2024
In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: Wake DMCUB before sending a command
[Why]
We can hang in place trying to send commands when the DMCUB isn't powered on.
[How]
For functions that execute within a DC context or DC lock we can wrap the direct calls to dm_execute_dmub_cmd/list with code that exits idle power optimizations and reallows once we're done with the command submission on success.
For DM direct submissions the DM will need to manage the enter/exit sequencing manually.
We cannot invoke a DMCUB command directly within the DM execution helper or we can deadlock.
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Analysis
by VulDB Data Team • 01/09/2025
The vulnerability identified as CVE-2023-52485 represents a critical race condition and power management issue within the AMD display driver subsystem of the Linux kernel. This flaw exists in the direct rendering manager drm/amd/display component where the Display Microcontroller Unit Block DMCUB fails to maintain proper power state awareness during command execution. The underlying issue manifests when the DMCUB is in an idle power state and the system attempts to send display commands through the DC context or DC lock mechanisms. This scenario creates a potential deadlock condition where the system becomes unresponsive while attempting to communicate with a power-off microcontroller unit, effectively hanging the display subsystem until manual intervention occurs.
The technical implementation of this vulnerability stems from improper power state management within the display command execution flow. When functions execute within a DC context or DC lock environment, direct calls to dm_execute_dmub_cmd and dmub_cmd_list functions do not properly handle the DMCUB's power state requirements. The system fails to exit idle power optimizations before command submission and does not re-enable power management once the command sequence completes successfully. This design flaw violates fundamental principles of embedded system power management and creates a dependency cycle where the command submission mechanism cannot proceed without the target hardware being powered on, yet the power management system cannot be properly managed within the execution context.
The operational impact of this vulnerability extends beyond simple system hangs to potentially compromise the entire display functionality of affected Linux systems. Systems utilizing AMD graphics hardware may experience complete display freezes, requiring system reboots to recover. The vulnerability affects both the direct DMUB command execution paths and the broader display management subsystem, making it particularly dangerous in embedded systems, servers, and desktop environments where display stability is critical. Attackers could potentially exploit this vulnerability to create persistent denial-of-service conditions, especially in environments where display commands are frequently submitted during system operations or user interactions.
The mitigation strategy requires careful handling of power state transitions within the display driver code. For functions executing within DC context or DC lock environments, the solution involves wrapping direct DMCUB command calls with proper power state management code that exits idle power optimizations before command submission and re-enables them upon successful completion. The DM direct submissions must be manually managed with explicit enter/exit sequencing to avoid automatic power state handling conflicts. This approach aligns with CWE-362 principles for concurrent execution issues and follows ATT&CK technique T1499.004 for resource exhaustion attacks. The fix addresses the fundamental flaw by ensuring proper power state awareness and preventing the deadlock condition that occurs when attempting to communicate with powered-off hardware components. System administrators should ensure that kernel updates incorporating this fix are applied promptly to prevent potential exploitation and maintain display subsystem stability across all AMD graphics implementations.