Linux Kernel AMD GPU Synchronization Vulnerability in DMA Buffer Handling

A synchronization vulnerability has been addressed in the Linux kernel's AMD GPU driver, specifically in the handling of DMA buffers. The issue arose because invalidating a DMA buffer could disrupt other processes using the same buffer object. The vulnerability was caused by improper synchronization when updating page tables, which could lead to page faults during concurrent GPU operations. This issue was particularly relevant on systems without PCI peer-to-peer support, where the mismanagement of buffer moves between GPUs could interfere with ongoing rendering tasks.

Impact

The vulnerability could cause page faults by improperly synchronizing DMA buffer moves between processes using different GPUs, disrupting ongoing graphics operations.

Reproduction

To reproduce this vulnerability, run 'glxgears' on GPU0 and 'Xorg' on GPU1, on a system where PCI peer-to-peer is not supported. Export a linear buffer from GPU0 and import it using GPU1. After submitting a frame rendering job on GPU0, initiate a tiled-to-linear blit, and then copy the linear buffer in Xorg running on GPU1. This sequence will likely cause a page fault due to the unsynchronized buffer move.

Remediation

Users can upgrade to the latest version of the Linux kernel where this vulnerability has been fixed.