scsi: lpfc: Fix a possible null pointer dereference

In function lpfc_xcvr_data_show, the memory allocation with kmalloc might
fail, thereby making rdp_context a null pointer. In the following context
and functions that use this pointer, there are dereferencing operations,
leading to null pointer dereference.

To fix this issue, a null pointer check should be added. If it is null,
use scnprintf to notify the user and return len.

Fixes: 479b091 ("scsi: lpfc: Create a sysfs entry called lpfc_xcvr_data for transceiver info")
Signed-off-by: Huai-Yuan Liu <qq810974084@gmail.com>
Link: https://lore.kernel.org/r/20240621082545.449170-1-qq810974084@gmail.com
Reviewed-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc_attr.c

@@ -1907,6 +1907,11 @@ lpfc_xcvr_data_show(struct device *dev, struct device_attribute *attr,
 
 	/* Get transceiver information */
 	rdp_context = kmalloc(sizeof(*rdp_context), GFP_KERNEL);
+	if (!rdp_context) {
+		len = scnprintf(buf, PAGE_SIZE - len,
+				"SPF info NA: alloc failure\n");
+		return len;
+	}
 
 	rc = lpfc_get_sfp_info_wait(phba, rdp_context);
 	if (rc) {