scsi: pm80xx: Fix pm8001_mpi_get_nvmd_resp() race condition

A use-after-free or null-pointer error occurs when the 251-byte response
data is copied from IOMB buffer to response message buffer in function
pm8001_mpi_get_nvmd_resp().

After sending the command get_nvmd_data(), the caller begins to sleep by
calling wait_for_complete() and waits for the wake-up from calling
complete() in pm8001_mpi_get_nvmd_resp(). Due to unexpected events (e.g.,
interrupt), if response buffer gets freed before memcpy(), a use-after-free
error will occur. To fix this, the complete() should be called after
memcpy().

Link: https://lore.kernel.org/r/20201102165528.26510-5-Viswas.G@microchip.com.comAcked-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: yuuzheng <yuuzheng@google.com>
Signed-off-by: Viswas G <Viswas.G@microchip.com>
Signed-off-by: Ruksar Devadi <Ruksar.devadi@microchip.com>
Signed-off-by: Radha Ramachandran <radha@google.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/pm8001/pm8001_hwi.c

@@ -3279,10 +3279,15 @@ pm8001_mpi_get_nvmd_resp(struct pm8001_hba_info *pm8001_ha, void *piomb)
 		pm8001_ha->memoryMap.region[NVMD].virt_ptr,
 		fw_control_context->len);
 	kfree(ccb->fw_control_context);
+	/* To avoid race condition, complete should be
+	 * called after the message is copied to
+	 * fw_control_context->usrAddr
+	 */
+	complete(pm8001_ha->nvmd_completion);
+	PM8001_MSG_DBG(pm8001_ha, pm8001_printk("Set nvm data complete!\n"));
 	ccb->task = NULL;
 	ccb->ccb_tag = 0xFFFFFFFF;
 	pm8001_tag_free(pm8001_ha, tag);
-	complete(pm8001_ha->nvmd_completion);
 }
 
 int pm8001_mpi_local_phy_ctl(struct pm8001_hba_info *pm8001_ha, void *piomb)