CVE-2022-48766 in Linux
Summary
by MITRE • 06/20/2024
In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: Wrap dcn301_calculate_wm_and_dlg for FPU.
Mirrors the logic for dcn30. Cue lots of WARNs and some kernel panics without this fix.
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Analysis
by VulDB Data Team • 01/07/2025
The vulnerability identified as CVE-2022-48766 resides within the Linux kernel's graphics subsystem, specifically affecting the AMD display driver component known as drm/amd/display. This issue manifests in the dcn301_calculate_wm_and_dlg function which handles display watermark and dialog calculations for AMD's DCN301 graphics hardware. The problem stems from improper handling of floating point unit operations within this critical display calculation routine, creating a scenario where the kernel fails to properly manage FPU state during these computations. The vulnerability represents a classic case of inadequate floating point context management that can lead to system instability and potential denial of service conditions.
The technical flaw occurs when the dcn301_calculate_wm_and_dlg function performs floating point arithmetic operations without proper FPU state preservation or restoration. This function is part of the display memory management system that calculates watermark values and dialog timing parameters essential for proper display operation. Without the proper FPU wrapping mechanism, floating point operations can corrupt the processor's floating point unit state, leading to unpredictable behavior in the graphics subsystem. The absence of this wrapping creates a condition where floating point exceptions or state inconsistencies can propagate through the kernel, causing kernel warnings and in severe cases, complete system panics. This type of vulnerability aligns with CWE-122 which addresses buffer overflow conditions, though specifically in the context of floating point unit state management rather than traditional buffer issues.
The operational impact of CVE-2022-48766 extends beyond simple display glitches to potentially compromise entire system stability. When the FPU state becomes corrupted during display calculations, the kernel generates numerous WARN messages indicating the occurrence of floating point exceptions and inconsistent state conditions. These warnings often precede more serious kernel panics that can result in complete system crashes, forcing users to reboot their systems. The vulnerability is particularly concerning in server and workstation environments where continuous operation is critical, as display subsystem failures can cascade into broader system instability. The issue affects systems running Linux kernels with AMD graphics hardware implementing DCN301 display controllers, making it relevant to a wide range of computing platforms including desktops, laptops, and server configurations with AMD Radeon graphics.
The mitigation for this vulnerability involves applying the kernel patch that properly wraps the dcn301_calculate_wm_and_dlg function with appropriate FPU state management. This fix ensures that floating point unit context is properly saved and restored during the execution of display calculation routines, preventing state corruption that leads to warnings and kernel panics. System administrators should prioritize updating their Linux kernel versions to include this patch, particularly in production environments where display stability is paramount. The solution follows established security practices for managing floating point unit operations in kernel space, similar to techniques outlined in the Linux kernel security documentation and ATT&CK framework category TA0005 (Defense Evasion) where improper state management can lead to system instability and denial of service conditions. Organizations should implement comprehensive patch management procedures to ensure all systems with AMD graphics hardware receive this critical update, as the vulnerability can be exploited through normal display operations without requiring special privileges or user interaction.