CVE-2026-90286 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/amdgpu/gfx6: Use PFP on the compute queues too
On GFX6, the compute rings use the same CP path as the graphics ring. The only difference is that they don't support draw commands. (As opposed to GFX7 and newer which have a separate command parser that is called MEC for compute queues.)
This means that we have to take into consideration that the PFP also exists on compute queues on GFX6:
Use PFP for register writes on both graphics and compute queues.
In the pipeline sync, use the PFP to wait for the previous fence (and not the ME) to prevent the PFP from starting to execute the next submission while the ME is still in the previous submission.
After a VM flush, emit PFP_SYNC_ME on compute queues as well.
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Analysis
by VulDB Data Team • 09/17/2026
The Linux kernel driver for AMD Graphics Processing Units contains a specific synchronization flaw within the GFX6 architecture that affects how command submissions are handled across graphics and compute rings. In this hardware generation, the Compute Processor utilizes the same Command Parser path as the standard graphics ring, differing only in its inability to execute draw commands. This architectural shared pathway implies that pipeline control mechanisms designed for graphics must also be correctly applied to compute operations. The vulnerability arises from an oversight where certain synchronization primitives were not consistently enforced on compute queues, leading to potential race conditions and improper execution ordering between different stages of the GPU command stream.
The core technical flaw involves the incorrect handling of Pipeline Fence (PFP) instructions during register writes and pipeline synchronization events. Specifically, the driver failed to utilize PFP for register writes on both graphics and compute queues in a uniform manner. More critically, within the pipeline sync logic, the system was incorrectly using the Microengine (ME) to wait for previous fences rather than relying on the PFP mechanism. This misconfiguration allows the PFP unit to begin executing commands from a new submission while the ME is still processing instructions from the preceding submission. Such an overlap creates a race condition where hardware state may be corrupted or inconsistent because subsequent operations proceed before prior dependencies are fully resolved at the hardware level.
The operational impact of this vulnerability includes potential graphical artifacts, system instability, and in severe cases, kernel panics due to illegal memory access or undefined behavior resulting from out-of-order execution. Because GPU command streams rely heavily on strict ordering guarantees provided by synchronization primitives like fences and semaphores, bypassing the correct PFP wait mechanism undermines these guarantees. Attackers with local user privileges could potentially exploit this timing window to trigger unintended side effects within the graphics subsystem, although exploitation typically requires precise control over submission queues which is often restricted by standard privilege boundaries. The issue primarily affects stability and correctness rather than providing a direct path for arbitrary code execution in most scenarios, but it represents a significant deviation from expected hardware behavior defined by AMD's specifications.
To mitigate this vulnerability, the Linux kernel has been updated to enforce the use of PFP for register writes on both graphics and compute queues uniformly. The pipeline synchronization logic has been corrected to utilize the PFP mechanism to wait for previous fences instead of relying on the ME state. Additionally, after Virtual Memory (VM) flush operations, the driver now correctly emits a PFP_SYNC_ME command on compute queues as well. These changes ensure that all stages of the GPU pipeline are properly synchronized before proceeding with new submissions, thereby eliminating the race condition and restoring correct execution ordering across both graphics and compute workloads. Users should update their systems to include this kernel patch to maintain system stability and prevent potential crashes associated with concurrent GPU workload scheduling on GFX6 hardware.