Affected: Linux

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

drm/imagination: Fix double call to drm_sched_entity_fini()

Call sequence of double call: pvr_context_destroy   pvr_context_kill_queues     pvr_queue_kill       drm_sched_entity_destroy         drm_sched_entity_fini // here   pvr_context_put     kref_put(..., pvr_context_release)       pvr_context_destroy_queues         pvr_queue_destroy           drm_sched_entity_fini // here

Call to drm_sched_entity_destroy() from pvr_context_kill_queues() calls drm_sched_entity_flush() + drm_sched_entity_fini(). drm_sched_entity_flush() ensures all pending jobs are completed and drm_sched_entity_fini() ensures no further submission is allowed as per expectation from pvr_context_kill_queues(). Double call to drm_sched_entity_fini() is misuse of the API so keep call only in pvr_context_create() failure path.

Stack trace for issue with addition of refcounting for DRM entity stats in commit fd177135f0e6 ("drm/sched: Account entity GPU time"):

[ 789.490527] ------------[ cut here ]------------ [ 789.490559] refcount_t: underflow; use-after-free. [ 789.490657] WARNING: lib/refcount.c:28 at refcount_warn_saturate+0xf4/0x144, CPU#0: kworker/u16:1/440 [ 789.490695] Modules linked in: powervr drm_gpuvm drm_exec gpu_sched drm_shmem_helper xhci_plat_hcd xhci_hcd dwc3 usbcore usb_common snd_soc_simple_card snd_soc_simple_card_utils sa2ul sha512 sha256 dwc3_am62 sha1 authenc rti_wdt libsha512 at24 sch_fq_codel fuse dm_mod ipv6…