scsi: hisi_sas: Fix NULL pointer dereference

There is a NULL pointer dereference in case *slot* happens to be NULL at
lines 1053 and 1878:

struct hisi_sas_cq *cq =
	&hisi_hba->cq[slot->dlvry_queue];

Notice that *slot* is being NULL checked at lines 1057 and 1881:
if (slot), which implies it may be NULL.

Fix this by placing the declaration and definition of variable cq, which
contains the pointer dereference slot->dlvry_queue, after slot has been
properly NULL checked.

Addresses-Coverity-ID: 1474515 ("Dereference before null check")
Addresses-Coverity-ID: 1474520 ("Dereference before null check")
Fixes: 584f53fe5f52 ("scsi: hisi_sas: Fix the race between IO completion and timeout for SMP/internal IO")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/hisi_sas/hisi_sas_main.c

@@ -1050,11 +1050,11 @@ static int hisi_sas_exec_internal_tmf_task(struct domain_device *device,
 		if ((task->task_state_flags & SAS_TASK_STATE_ABORTED)) {
 			if (!(task->task_state_flags & SAS_TASK_STATE_DONE)) {
 				struct hisi_sas_slot *slot = task->lldd_task;
-				struct hisi_sas_cq *cq =
-					&hisi_hba->cq[slot->dlvry_queue];
 
 				dev_err(dev, "abort tmf: TMF task timeout and not done\n");
 				if (slot) {
+					struct hisi_sas_cq *cq =
+					       &hisi_hba->cq[slot->dlvry_queue];
 					/*
 					 * flush tasklet to avoid free'ing task
 					 * before using task in IO completion
@@ -1875,10 +1875,10 @@ hisi_sas_internal_task_abort(struct hisi_hba *hisi_hba,
 	if ((task->task_state_flags & SAS_TASK_STATE_ABORTED)) {
 		if (!(task->task_state_flags & SAS_TASK_STATE_DONE)) {
 			struct hisi_sas_slot *slot = task->lldd_task;
-			struct hisi_sas_cq *cq =
-				&hisi_hba->cq[slot->dlvry_queue];
 
 			if (slot) {
+				struct hisi_sas_cq *cq =
+					&hisi_hba->cq[slot->dlvry_queue];
 				/*
 				 * flush tasklet to avoid free'ing task
 				 * before using task in IO completion