Bug 2468060 (CVE-2026-43318)

Summary: CVE-2026-43318 kernel: drm/amdgpu: fix sync handling in amdgpu_dma_buf_move_notify
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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OS: Linux   
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A flaw was found in the Linux kernel's drm/amdgpu component. A synchronization bug in the amdgpu_dma_buf_move_notify function, which handles direct memory access buffer (dmabuf) movements, can lead to a page fault. This occurs when a process attempts to access a shared buffer while another process is still updating its page table after a buffer move, potentially causing a system crash or denial of service.
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Description OSIDB Bzimport 2026-05-08 14:02:27 UTC 
In the Linux kernel, the following vulnerability has been resolved:

drm/amdgpu: fix sync handling in amdgpu_dma_buf_move_notify

Invalidating a dmabuf will impact other users of the shared BO.
In the scenario where process A moves the BO, it needs to inform
process B about the move and process B will need to update its
page table.

The commit fixes a synchronisation bug caused by the use of the
ticket: it made amdgpu_vm_handle_moved behave as if updating
the page table immediately was correct but in this case it's not.

An example is the following scenario, with 2 GPUs and glxgears
running on GPU0 and Xorg running on GPU1, on a system where P2P
PCI isn't supported:

glxgears:
  export linear buffer from GPU0 and import using GPU1
  submit frame rendering to GPU0
  submit tiled->linear blit
Xorg:
  copy of linear buffer

The sequence of jobs would be:
  drm_sched_job_run                       # GPU0, frame rendering
  drm_sched_job_queue                     # GPU0, blit
  drm_sched_job_done                      # GPU0, frame rendering
  drm_sched_job_run                       # GPU0, blit
  move linear buffer for GPU1 access      #
  amdgpu_dma_buf_move_notify -> update pt # GPU0

It this point the blit job on GPU0 is still running and would
likely produce a page fault.
Comment 1 Keith Grant 2026-05-08 19:12:33 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026050818-CVE-2026-43318-79ab@gregkh/T