scsi: storvsc: Validate length of incoming packet in storvsc_on_channel_callback()

Check that the packet is of the expected size at least, don't copy data
past the packet.

Link: https://lore.kernel.org/r/20201118145348.109879-1-parri.andrea@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
Reported-by: Saruhan Karademir <skarade@microsoft.com>
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/storvsc_drv.c

@@ -1246,6 +1246,11 @@ static void storvsc_on_channel_callback(void *context)
 		request = (struct storvsc_cmd_request *)
 			((unsigned long)desc->trans_id);
 
+		if (hv_pkt_datalen(desc) < sizeof(struct vstor_packet) - vmscsi_size_delta) {
+			dev_err(&device->device, "Invalid packet len\n");
+			continue;
+		}
+
 		if (request == &stor_device->init_request ||
 		    request == &stor_device->reset_request) {
 			memcpy(&request->vstor_packet, packet,