Merge tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi

Pull SCSI fixes from James Bottomley:
 "Eight patches which looks like quite a large core change, but most of
  the diffstat is reverting the attempt to rejig reference counting
  introduced in the last merge window which caused issues with device
  and module removal.

  Of the remaining four patches, only the fix use-after-free is
  substantial"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  scsi: mpt3sas: Fix use-after-free warning
  scsi: core: Fix a use-after-free
  scsi: core: Revert "Make sure that targets outlive devices"
  scsi: core: Revert "Make sure that hosts outlive targets"
  scsi: core: Revert "Simplify LLD module reference counting"
  scsi: core: Revert "Call blk_mq_free_tag_set() earlier"
  scsi: lpfc: Add missing destroy_workqueue() in error path
  scsi: lpfc: Return DID_TRANSPORT_DISRUPTED instead of DID_REQUEUE

drivers/scsi/hosts.c

@@ -182,6 +182,15 @@ void scsi_remove_host(struct Scsi_Host *shost)
 	mutex_unlock(&shost->scan_mutex);
 	scsi_proc_host_rm(shost);
 
+	/*
+	 * New SCSI devices cannot be attached anymore because of the SCSI host
+	 * state so drop the tag set refcnt. Wait until the tag set refcnt drops
+	 * to zero because .exit_cmd_priv implementations may need the host
+	 * pointer.
+	 */
+	kref_put(&shost->tagset_refcnt, scsi_mq_free_tags);
+	wait_for_completion(&shost->tagset_freed);
+
 	spin_lock_irqsave(shost->host_lock, flags);
 	if (scsi_host_set_state(shost, SHOST_DEL))
 		BUG_ON(scsi_host_set_state(shost, SHOST_DEL_RECOVERY));
@@ -190,15 +199,6 @@ void scsi_remove_host(struct Scsi_Host *shost)
 	transport_unregister_device(&shost->shost_gendev);
 	device_unregister(&shost->shost_dev);
 	device_del(&shost->shost_gendev);
-
-	/*
-	 * After scsi_remove_host() has returned the scsi LLD module can be
-	 * unloaded and/or the host resources can be released. Hence wait until
-	 * the dependent SCSI targets and devices are gone before returning.
-	 */
-	wait_event(shost->targets_wq, atomic_read(&shost->target_count) == 0);
-
-	scsi_mq_destroy_tags(shost);
 }
 EXPORT_SYMBOL(scsi_remove_host);
 
@@ -254,6 +254,9 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
 	if (error)
 		goto fail;
 
+	kref_init(&shost->tagset_refcnt);
+	init_completion(&shost->tagset_freed);
+
 	/*
 	 * Increase usage count temporarily here so that calling
 	 * scsi_autopm_put_host() will trigger runtime idle if there is
@@ -309,8 +312,8 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
 	return error;
 
 	/*
-	 * Any resources associated with the SCSI host in this function except
-	 * the tag set will be freed by scsi_host_dev_release().
+	 * Any host allocation in this function will be freed in
+	 * scsi_host_dev_release().
 	 */
  out_del_dev:
 	device_del(&shost->shost_dev);
@@ -326,7 +329,7 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
 	pm_runtime_disable(&shost->shost_gendev);
 	pm_runtime_set_suspended(&shost->shost_gendev);
 	pm_runtime_put_noidle(&shost->shost_gendev);
-	scsi_mq_destroy_tags(shost);
+	kref_put(&shost->tagset_refcnt, scsi_mq_free_tags);
  fail:
 	return error;
 }
@@ -406,7 +409,6 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 	INIT_LIST_HEAD(&shost->starved_list);
 	init_waitqueue_head(&shost->host_wait);
 	mutex_init(&shost->scan_mutex);
-	init_waitqueue_head(&shost->targets_wq);
 
 	index = ida_alloc(&host_index_ida, GFP_KERNEL);
 	if (index < 0) {

drivers/scsi/lpfc/lpfc_init.c

@@ -8053,7 +8053,7 @@ lpfc_sli4_driver_resource_setup(struct lpfc_hba *phba)
 	/* Allocate device driver memory */
 	rc = lpfc_mem_alloc(phba, SGL_ALIGN_SZ);
 	if (rc)
-		return -ENOMEM;
+		goto out_destroy_workqueue;
 
 	/* IF Type 2 ports get initialized now. */
 	if (bf_get(lpfc_sli_intf_if_type, &phba->sli4_hba.sli_intf) >=
@@ -8481,6 +8481,9 @@ lpfc_sli4_driver_resource_setup(struct lpfc_hba *phba)
 	lpfc_destroy_bootstrap_mbox(phba);
 out_free_mem:
 	lpfc_mem_free(phba);
+out_destroy_workqueue:
+	destroy_workqueue(phba->wq);
+	phba->wq = NULL;
 	return rc;
 }
 

drivers/scsi/lpfc/lpfc_scsi.c

@@ -4272,7 +4272,7 @@ lpfc_fcp_io_cmd_wqe_cmpl(struct lpfc_hba *phba, struct lpfc_iocbq *pwqeIn,
 		    lpfc_cmd->result == IOERR_ABORT_REQUESTED ||
 		    lpfc_cmd->result == IOERR_RPI_SUSPENDED ||
 		    lpfc_cmd->result == IOERR_SLER_CMD_RCV_FAILURE) {
-			cmd->result = DID_REQUEUE << 16;
+			cmd->result = DID_TRANSPORT_DISRUPTED << 16;
 			break;
 		}
 		if ((lpfc_cmd->result == IOERR_RX_DMA_FAILED ||
@@ -4562,7 +4562,7 @@ lpfc_scsi_cmd_iocb_cmpl(struct lpfc_hba *phba, struct lpfc_iocbq *pIocbIn,
 			    lpfc_cmd->result == IOERR_NO_RESOURCES ||
 			    lpfc_cmd->result == IOERR_ABORT_REQUESTED ||
 			    lpfc_cmd->result == IOERR_SLER_CMD_RCV_FAILURE) {
-				cmd->result = DID_REQUEUE << 16;
+				cmd->result = DID_TRANSPORT_DISRUPTED << 16;
 				break;
 			}
 			if ((lpfc_cmd->result == IOERR_RX_DMA_FAILED ||

drivers/scsi/mpt3sas/mpt3sas_scsih.c

@@ -3670,6 +3670,7 @@ static struct fw_event_work *dequeue_next_fw_event(struct MPT3SAS_ADAPTER *ioc)
 		fw_event = list_first_entry(&ioc->fw_event_list,
 				struct fw_event_work, list);
 		list_del_init(&fw_event->list);
+		fw_event_work_put(fw_event);
 	}
 	spin_unlock_irqrestore(&ioc->fw_event_lock, flags);
 
@@ -3751,7 +3752,6 @@ _scsih_fw_event_cleanup_queue(struct MPT3SAS_ADAPTER *ioc)
 		if (cancel_work_sync(&fw_event->work))
 			fw_event_work_put(fw_event);
 
-		fw_event_work_put(fw_event);
 	}
 	ioc->fw_events_cleanup = 0;
 }

drivers/scsi/scsi.c

@@ -586,13 +586,10 @@ EXPORT_SYMBOL(scsi_device_get);
  */
 void scsi_device_put(struct scsi_device *sdev)
 {
-	/*
-	 * Decreasing the module reference count before the device reference
-	 * count is safe since scsi_remove_host() only returns after all
-	 * devices have been removed.
-	 */
-	module_put(sdev->host->hostt->module);
+	struct module *mod = sdev->host->hostt->module;
+
 	put_device(&sdev->sdev_gendev);
+	module_put(mod);
 }
 EXPORT_SYMBOL(scsi_device_put);
 

drivers/scsi/scsi_lib.c

@@ -1983,9 +1983,13 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
 	return blk_mq_alloc_tag_set(tag_set);
 }
 
-void scsi_mq_destroy_tags(struct Scsi_Host *shost)
+void scsi_mq_free_tags(struct kref *kref)
 {
+	struct Scsi_Host *shost = container_of(kref, typeof(*shost),
+					       tagset_refcnt);
+
 	blk_mq_free_tag_set(&shost->tag_set);
+	complete(&shost->tagset_freed);
 }
 
 /**

drivers/scsi/scsi_priv.h

@@ -94,7 +94,7 @@ extern void scsi_run_host_queues(struct Scsi_Host *shost);
 extern void scsi_requeue_run_queue(struct work_struct *work);
 extern void scsi_start_queue(struct scsi_device *sdev);
 extern int scsi_mq_setup_tags(struct Scsi_Host *shost);
-extern void scsi_mq_destroy_tags(struct Scsi_Host *shost);
+extern void scsi_mq_free_tags(struct kref *kref);
 extern void scsi_exit_queue(void);
 extern void scsi_evt_thread(struct work_struct *work);
 

drivers/scsi/scsi_scan.c

@@ -340,6 +340,7 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
 		kfree(sdev);
 		goto out;
 	}
+	kref_get(&sdev->host->tagset_refcnt);
 	sdev->request_queue = q;
 	q->queuedata = sdev;
 	__scsi_init_queue(sdev->host, q);
@@ -406,14 +407,9 @@ static void scsi_target_destroy(struct scsi_target *starget)
 static void scsi_target_dev_release(struct device *dev)
 {
 	struct device *parent = dev->parent;
-	struct Scsi_Host *shost = dev_to_shost(parent);
 	struct scsi_target *starget = to_scsi_target(dev);
 
 	kfree(starget);
-
-	if (atomic_dec_return(&shost->target_count) == 0)
-		wake_up(&shost->targets_wq);
-
 	put_device(parent);
 }
 
@@ -526,10 +522,6 @@ static struct scsi_target *scsi_alloc_target(struct device *parent,
 	starget->state = STARGET_CREATED;
 	starget->scsi_level = SCSI_2;
 	starget->max_target_blocked = SCSI_DEFAULT_TARGET_BLOCKED;
-	init_waitqueue_head(&starget->sdev_wq);
-
-	atomic_inc(&shost->target_count);
-
  retry:
 	spin_lock_irqsave(shost->host_lock, flags);
 

drivers/scsi/scsi_sysfs.c

@@ -443,15 +443,18 @@ static void scsi_device_cls_release(struct device *class_dev)
 
 static void scsi_device_dev_release_usercontext(struct work_struct *work)
 {
-	struct scsi_device *sdev = container_of(work, struct scsi_device,
-						ew.work);
-	struct scsi_target *starget = sdev->sdev_target;
+	struct scsi_device *sdev;
 	struct device *parent;
 	struct list_head *this, *tmp;
 	struct scsi_vpd *vpd_pg80 = NULL, *vpd_pg83 = NULL;
 	struct scsi_vpd *vpd_pg0 = NULL, *vpd_pg89 = NULL;
 	struct scsi_vpd *vpd_pgb0 = NULL, *vpd_pgb1 = NULL, *vpd_pgb2 = NULL;
 	unsigned long flags;
+	struct module *mod;
+
+	sdev = container_of(work, struct scsi_device, ew.work);
+
+	mod = sdev->host->hostt->module;
 
 	scsi_dh_release_device(sdev);
 
@@ -513,16 +516,19 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
 	kfree(sdev->inquiry);
 	kfree(sdev);
 
-	if (starget && atomic_dec_return(&starget->sdev_count) == 0)
-		wake_up(&starget->sdev_wq);
-
 	if (parent)
 		put_device(parent);
+	module_put(mod);
 }
 
 static void scsi_device_dev_release(struct device *dev)
 {
 	struct scsi_device *sdp = to_scsi_device(dev);
+
+	/* Set module pointer as NULL in case of module unloading */
+	if (!try_module_get(sdp->host->hostt->module))
+		sdp->host->hostt->module = NULL;
+
 	execute_in_process_context(scsi_device_dev_release_usercontext,
 				   &sdp->ew);
 }
@@ -1470,6 +1476,7 @@ void __scsi_remove_device(struct scsi_device *sdev)
 	mutex_unlock(&sdev->state_mutex);
 
 	blk_mq_destroy_queue(sdev->request_queue);
+	kref_put(&sdev->host->tagset_refcnt, scsi_mq_free_tags);
 	cancel_work_sync(&sdev->requeue_work);
 
 	if (sdev->host->hostt->slave_destroy)
@@ -1529,14 +1536,6 @@ static void __scsi_remove_target(struct scsi_target *starget)
 		goto restart;
 	}
 	spin_unlock_irqrestore(shost->host_lock, flags);
-
-	/*
-	 * After scsi_remove_target() returns its caller can remove resources
-	 * associated with @starget, e.g. an rport or session. Wait until all
-	 * devices associated with @starget have been removed to prevent that
-	 * a SCSI error handling callback function triggers a use-after-free.
-	 */
-	wait_event(starget->sdev_wq, atomic_read(&starget->sdev_count) == 0);
 }
 
 /**
@@ -1647,9 +1646,6 @@ void scsi_sysfs_device_initialize(struct scsi_device *sdev)
 	list_add_tail(&sdev->same_target_siblings, &starget->devices);
 	list_add_tail(&sdev->siblings, &shost->__devices);
 	spin_unlock_irqrestore(shost->host_lock, flags);
-
-	atomic_inc(&starget->sdev_count);
-
 	/*
 	 * device can now only be removed via __scsi_remove_device() so hold
 	 * the target.  Target will be held in CREATED state until something

include/scsi/scsi_device.h

@@ -309,8 +309,6 @@ struct scsi_target {
 	struct list_head	devices;
 	struct device		dev;
 	struct kref		reap_ref; /* last put renders target invisible */
-	atomic_t		sdev_count;
-	wait_queue_head_t	sdev_wq;
 	unsigned int		channel;
 	unsigned int		id; /* target id ... replace
 				     * scsi_device.id eventually */

include/scsi/scsi_host.h

@@ -557,6 +557,8 @@ struct Scsi_Host {
 	struct scsi_host_template *hostt;
 	struct scsi_transport_template *transportt;
 
+	struct kref		tagset_refcnt;
+	struct completion	tagset_freed;
 	/* Area to keep a shared tag map */
 	struct blk_mq_tag_set	tag_set;
 
@@ -690,9 +692,6 @@ struct Scsi_Host {
 	/* ldm bits */
 	struct device		shost_gendev, shost_dev;
 
-	atomic_t		target_count;
-	wait_queue_head_t	targets_wq;
-
 	/*
 	 * Points to the transport data (if any) which is allocated
 	 * separately