CVE-2026-68384

In the Linux kernel, the following vulnerability has been resolved:

drm/xe/vf: Fix VF CCS attach/detach race with in-flight BO moves

xe_bo_move() attaches VF CCS read/write batch buffers (BBs) to a BO

after it transitions NULL/SYSTEM -> TT, and detaches them after it

transitions TT -> SYSTEM. Both operations were done synchronously on

the CPU immediately after building the move's copy/clear fence,

without waiting for that fence to signal. This creates two races with

VF migration:

- Attach happens too late relative to the copy job it is meant to

protect. If the copy job is submitted before the CCS BBs are

attached, a VF migration event that pauses execution mid-copy can

observe partially copied CCS metadata without the attach state

needed to correctly save/restore it.

- Detach happens too early relative to the copy job that moves data

out of TT. The CCS BBs are torn down right after the copy fence is

obtained, while the actual blit may still be in flight. A VF

migration event that pauses execution mid-copy can then race the

save/restore path against the still-running blit, and the CCS BBs

it would need to make sense of the paused state have already been

removed.

Fix both races:

- Move the attach call to before the copy/clear job is submitted, so

the CCS BBs are already registered by the time the copy runs. On

attach failure, unwind and bail out of the move. xe_migrate_ccs_rw_copy()

now takes the destination resource explicitly, since bo->ttm.resource

is not updated to the new resource until after the move commits.

- Detach only after explicitly waiting for the copy fence to signal,

instead of tearing down the CCS BBs immediately after obtaining it.

While here, also fix xe_sriov_vf_ccs_attach_bo() to properly unwind and

propagate errors: the per-context loop previously never broke out on

error, silently discarding earlier failures. Unwind by clearing each

attached context directly via xe_migrate_ccs_rw_copy_clear() instead of

reusing xe_sriov_vf_ccs_detach_bo(), which requires both contexts to be

attached before it will clean up either one.

(cherry picked from commit d45ad0aa7a1eb5d7288b5ed948b05695611dc39e)