CVE-2026-89807

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

drm/amdkfd: guard against NULL restore_mqd in CRIU queue restore

Both create_queue_cpsch() and create_queue_nocpsch() unconditionally
call mqd_mgr->restore_mqd() when a CRIU restore is in progress
(qd != NULL), with no NULL guard. On any system where restore_mqd is
not implemented for the given queue type, a user holding
CAP_CHECKPOINT_RESTORE can trigger a kernel NULL pointer dereference
and panic the machine by issuing KFD_IOC_CRIU_OP_RESTORE with a
crafted queue restore object. Note that checkpoint_mqd is likewise
unimplemented on GFX12, so no legitimate CRIU image can reach this
path — only a hand-crafted restore payload.

Add a NULL guard for restore_mqd immediately after mqd_mgr is
resolved, unwinding via the existing error labels and returning
-EOPNOTSUPP if the callback is not implemented. This mirrors the
existing checkpoint_mqd guard in checkpoint_mqd().