scsi: storvsc: Add validation for untrusted Hyper-V values

For additional robustness in the face of Hyper-V errors or malicious
behavior, validate all values that originate from packets that Hyper-V has
sent to the guest. Ensure that invalid values cannot cause data being
copied out of the bounds of the source buffer when calling memcpy. Ensure
that outgoing packets do not have any leftover guest memory that has not
been zeroed out.

Link: https://lore.kernel.org/r/20200706160928.53049-1-lkmlabelt@gmail.com
Cc: James E.J. Bottomley <jejb@linux.ibm.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Andres Beltran <lkmlabelt@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/storvsc_drv.c

@@ -1100,6 +1100,10 @@ static void storvsc_command_completion(struct storvsc_cmd_request *cmd_request,
 			data_transfer_length = 0;
 	}
 
+	/* Validate data_transfer_length (from Hyper-V) */
+	if (data_transfer_length > cmd_request->payload->range.len)
+		data_transfer_length = cmd_request->payload->range.len;
+
 	scsi_set_resid(scmnd,
 		cmd_request->payload->range.len - data_transfer_length);
 
@@ -1140,6 +1144,11 @@ static void storvsc_on_io_completion(struct storvsc_device *stor_device,
 	/* Copy over the status...etc */
 	stor_pkt->vm_srb.scsi_status = vstor_packet->vm_srb.scsi_status;
 	stor_pkt->vm_srb.srb_status = vstor_packet->vm_srb.srb_status;
+
+	/* Validate sense_info_length (from Hyper-V) */
+	if (vstor_packet->vm_srb.sense_info_length > sense_buffer_size)
+		vstor_packet->vm_srb.sense_info_length = sense_buffer_size;
+
 	stor_pkt->vm_srb.sense_info_length =
 	vstor_packet->vm_srb.sense_info_length;
 
@@ -1565,6 +1574,7 @@ static int storvsc_host_reset_handler(struct scsi_cmnd *scmnd)
 
 	request = &stor_device->reset_request;
 	vstor_packet = &request->vstor_packet;
+	memset(vstor_packet, 0, sizeof(struct vstor_packet));
 
 	init_completion(&request->wait_event);
 
@@ -1668,6 +1678,7 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
 	/* Setup the cmd request */
 	cmd_request->cmd = scmnd;
 
+	memset(&cmd_request->vstor_packet, 0, sizeof(struct vstor_packet));
 	vm_srb = &cmd_request->vstor_packet.vm_srb;
 	vm_srb->win8_extension.time_out_value = 60;