scsi: qedf: Fix crash when MFW calls for protocol stats while function is still probing

The MFW may make a call to qed and then to qedf for protocol statistics
while the function is still probing.  If this happens it's possible that
some members of the struct qedf_ctx may not be fully initialized which can
result in a NULL pointer dereference or general protection fault.

To prevent this, add a new flag call QEDF_PROBING and set it when the
__qedf_probe() function is active. Then in the qedf_get_protocol_tlv_data()
function we can check if the function is still probing and return
immediantely before any uninitialized structures can be touched.

Link: https://lore.kernel.org/r/20200416084314.18851-9-skashyap@marvell.comSigned-off-by: Chad Dupuis <cdupuis@marvell.com>
Signed-off-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/qedf/qedf.h

@@ -355,6 +355,7 @@ struct qedf_ctx {
 #define QEDF_GRCDUMP_CAPTURE		4
 #define QEDF_IN_RECOVERY		5
 #define QEDF_DBG_STOP_IO		6
+#define QEDF_PROBING			8
 	unsigned long flags; /* Miscellaneous state flags */
 	int fipvlan_retries;
 	u8 num_queues;

drivers/scsi/qedf/qedf_main.c

@@ -3190,7 +3190,7 @@ static int __qedf_probe(struct pci_dev *pdev, int mode)
 {
 	int rc = -EINVAL;
 	struct fc_lport *lport;
-	struct qedf_ctx *qedf;
+	struct qedf_ctx *qedf = NULL;
 	struct Scsi_Host *host;
 	bool is_vf = false;
 	struct qed_ll2_params params;
@@ -3220,6 +3220,7 @@ static int __qedf_probe(struct pci_dev *pdev, int mode)
 
 		/* Initialize qedf_ctx */
 		qedf = lport_priv(lport);
+		set_bit(QEDF_PROBING, &qedf->flags);
 		qedf->lport = lport;
 		qedf->ctlr.lp = lport;
 		qedf->pdev = pdev;
@@ -3244,9 +3245,12 @@ static int __qedf_probe(struct pci_dev *pdev, int mode)
 	} else {
 		/* Init pointers during recovery */
 		qedf = pci_get_drvdata(pdev);
+		set_bit(QEDF_PROBING, &qedf->flags);
 		lport = qedf->lport;
 	}
 
+	QEDF_INFO(&qedf->dbg_ctx, QEDF_LOG_DISC, "Probe started.\n");
+
 	host = lport->host;
 
 	/* Allocate mempool for qedf_io_work structs */
@@ -3553,6 +3557,10 @@ static int __qedf_probe(struct pci_dev *pdev, int mode)
 	else
 		fc_fabric_login(lport);
 
+	QEDF_INFO(&qedf->dbg_ctx, QEDF_LOG_DISC, "Probe done.\n");
+
+	clear_bit(QEDF_PROBING, &qedf->flags);
+
 	/* All good */
 	return 0;
 
@@ -3578,6 +3586,11 @@ static int __qedf_probe(struct pci_dev *pdev, int mode)
 err1:
 	scsi_host_put(lport->host);
 err0:
+	if (qedf) {
+		QEDF_INFO(&qedf->dbg_ctx, QEDF_LOG_DISC, "Probe done.\n");
+
+		clear_bit(QEDF_PROBING, &qedf->flags);
+	}
 	return rc;
 }
 
@@ -3727,11 +3740,25 @@ void qedf_get_protocol_tlv_data(void *dev, void *data)
 {
 	struct qedf_ctx *qedf = dev;
 	struct qed_mfw_tlv_fcoe *fcoe = data;
-	struct fc_lport *lport = qedf->lport;
-	struct Scsi_Host *host = lport->host;
-	struct fc_host_attrs *fc_host = shost_to_fc_host(host);
+	struct fc_lport *lport;
+	struct Scsi_Host *host;
+	struct fc_host_attrs *fc_host;
 	struct fc_host_statistics *hst;
 
+	if (!qedf) {
+		QEDF_ERR(NULL, "qedf is null.\n");
+		return;
+	}
+
+	if (test_bit(QEDF_PROBING, &qedf->flags)) {
+		QEDF_ERR(&qedf->dbg_ctx, "Function is still probing.\n");
+		return;
+	}
+
+	lport = qedf->lport;
+	host = lport->host;
+	fc_host = shost_to_fc_host(host);
+
 	/* Force a refresh of the fc_host stats including offload stats */
 	hst = qedf_fc_get_host_stats(host);