cxlflash: Fix to prevent workq from accessing freed memory

The workq can process work in parallel with a remove event, leading
to a condition where the workq handler can access freed memory.

To remedy, the workq should be terminated prior to freeing memory. Move
the termination call earlier in remove and use cancel_work_sync() instead
of flush_work() as there is not a need to process any scheduled work when
shutting down.
Signed-off-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Manoj N. Kumar <manoj@linux.vnet.ibm.com>
Reviewed-by: Brian King <brking@linux.vnet.ibm.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Odin.com>

drivers/scsi/cxlflash/main.c

@@ -736,11 +736,11 @@ static void cxlflash_remove(struct pci_dev *pdev)
 		/* Fall through */
 	case INIT_STATE_AFU:
 		term_afu(cfg);
+		cancel_work_sync(&cfg->work_q);
 	case INIT_STATE_PCI:
 		pci_release_regions(cfg->dev);
 		pci_disable_device(pdev);
 	case INIT_STATE_NONE:
-		flush_work(&cfg->work_q);
 		free_mem(cfg);
 		scsi_host_put(cfg->host);
 		break;