drm/xe/vm: nuke PTs only after unlinking contested VMAs

Summary

In the Linux kernel, the following vulnerability has been resolved: drm/xe/vm: nuke PTs only after unlinking contested VMAs In xe_vm_close_and_put(), external-BO VMAs are queued on the contested list for deferred destruction via xe_vma_destroy_unlocked(). However, xe_vm_pt_destroy() was previously invoked before processing contested VMAs, destroying vm->pt_root while those VMAs were still linked to their respective buffer objects (vm_bo->list.gpuva). If a concurrent thread evicts one of those shared buffer objects, xe_bo_trigger_rebind() holding only bo->resv walks the BO's VMAs and, in fault mode, calls xe_vm_invalidate_vma() -> xe_pt_zap_ptes(). Because vm->pt_root[tile->id] is already NULL, dereferencing pt->level causes a NULL ptr deref. Fix this by deferring xe_vm_free_scratch() and xe_vm_pt_destroy() until after all contested VMAs have been unlinked and destroyed. User is reporting hitting a NULL ptr deref in xe_pt_zap_ptes(), which could be explained by this race. (cherry picked from commit c2863648959489767f08892fd6e90577d2ea0b6a)

Timeline

1. Oct 18, 2026, 3:17 PM UTCCVE published
2. Oct 24, 2026, 2:09 PM UTCRecord last updated

Affected versions

• Linux Linux

  From b06d47be7c83165d3b3e45e1d5f9520b79c7f5cc · fixed in 70fddc065ac80845ffd33095b3635d59883cf7e6; From b06d47be7c83165d3b3e45e1d5f9520b79c7f5cc · fixed in ba678c2b02e0d36b53deb5a6d5e5ea044d36def7; From b06d47be7c83165d3b3e45e1d5f9520b79c7f5cc · fixed in bddaa5e4094c134452c29e20a26c4718827e4cb1; From b06d47be7c83165d3b3e45e1d5f9520b79c7f5cc · fixed in 24a22fb3c731474b68e986af6804db450fb88617

• Linux Linux

  6.8

• KernelLinux

  From 6.8.0 · fixed in 6.12.112; From 6.13.0 · fixed in 6.18.55; From 6.19.0 · fixed in 7.2.9

References 4