CVE-2023-52773 in Linux
Summary
by MITRE • 05/21/2024
In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: fix a NULL pointer dereference in amdgpu_dm_i2c_xfer()
When ddc_service_construct() is called, it explicitly checks both the link type and whether there is something on the link which will dictate whether the pin is marked as hw_supported.
If the pin isn't set or the link is not set (such as from unloading/reloading amdgpu in an IGT test) then fail the amdgpu_dm_i2c_xfer() call.
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Analysis
by VulDB Data Team • 05/21/2024
The vulnerability CVE-2023-52773 represents a critical NULL pointer dereference flaw within the AMD display driver subsystem of the Linux kernel specifically affecting the drm/amd/display component. This issue manifests in the amdgpu_dm_i2c_xfer() function where improper handling of display data channel (DDC) service construction leads to potential system crashes or denial of service conditions. The vulnerability occurs when the ddc_service_construct() function fails to properly validate hardware support conditions, creating a scenario where the system attempts to dereference a NULL pointer during I2C transfer operations.
The technical root cause stems from inadequate validation of display link states and hardware pin configurations within the AMD display driver implementation. When the ddc_service_construct() function processes display link initialization, it performs explicit checks on both link type and physical connection status to determine if a specific pin should be marked as hardware supported. However, under certain conditions such as driver module unloading and reloading during IGT testing scenarios, the function fails to properly establish these validation states, resulting in a NULL pointer reference when amdgpu_dm_i2c_xfer() attempts to process I2C transfers. This flaw aligns with CWE-476 which specifically addresses NULL pointer dereference vulnerabilities in software systems.
The operational impact of this vulnerability extends beyond simple system instability to potentially compromise the entire display functionality of affected systems. When triggered, the NULL pointer dereference can cause kernel oops messages, system crashes, or complete system lockups that require manual rebooting. The vulnerability is particularly concerning in server environments or embedded systems where display functionality may be critical for system management or user interface operations. Attackers could potentially exploit this weakness to cause persistent denial of service conditions, making systems unavailable for legitimate use while maintaining system stability for other operations.
The fix implemented for CVE-2023-52773 addresses the core issue by ensuring proper validation of display link states before proceeding with I2C transfer operations. When the ddc_service_construct() function detects that a pin is not properly set or the link is not established, it now properly fails the amdgpu_dm_i2c_xfer() call rather than allowing execution to continue with invalid pointers. This defensive programming approach prevents the kernel from attempting to access NULL memory locations while maintaining system stability. The resolution follows established security practices for preventing NULL pointer dereference conditions and aligns with ATT&CK framework techniques related to system resource exhaustion and denial of service attacks through kernel vulnerabilities. Organizations should prioritize applying this patch to prevent exploitation and maintain system reliability in environments where AMD graphics hardware is utilized. The fix demonstrates proper error handling mechanisms that should be implemented across similar kernel subsystems to prevent analogous vulnerabilities from emerging in other display driver components.