[Patch V2 2/2] MdeModulePkg/UsbMassStorageDxe: Check Get Max LUN status/value

[Michael D Kinney <michael.d.kinney@intel.com>]

https://bugzilla.tianocore.org/show_bug.cgi?id=767

If a USB Mass Storage device does not support the Get
Max LUN command, then the USB I/O Protocol ControlTransfer()
service may return an error.  If an error is returned for
this command, then assume that the device does not support
multiple LUNs and return a maximum LUN value of 0.

The USB Mass Storage Class Specification states that a
maximum LUN value larger than 0x0F is invalid.  Add
a check to make sure this maximum LUN value is in this
valid range, and if it is not, then assume that the
device does not support multiple LUNs and return a
maximum LUN value of 0.

This change improves compatibility with USB FLASH drives
that o not support the Get Max LUN command or return
an invalid maximum LUN value.

Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
---
 MdeModulePkg/Bus/Usb/UsbMassStorageDxe/UsbMassBot.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/MdeModulePkg/Bus/Usb/UsbMassStorageDxe/UsbMassBot.c b/MdeModulePkg/Bus/Usb/UsbMassStorageDxe/UsbMassBot.c
index 4bb7222b89..6afe2ae235 100644
--- a/MdeModulePkg/Bus/Usb/UsbMassStorageDxe/UsbMassBot.c
+++ b/MdeModulePkg/Bus/Usb/UsbMassStorageDxe/UsbMassBot.c
@@ -2,7 +2,7 @@
   Implementation of the USB mass storage Bulk-Only Transport protocol,
   according to USB Mass Storage Class Bulk-Only Transport, Revision 1.0.
 
-Copyright (c) 2007 - 2011, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2007 - 2017, Intel Corporation. All rights reserved.<BR>
 This program and the accompanying materials
 are licensed and made available under the terms and conditions of the BSD License
 which accompanies this distribution.  The full text of the license may be found at
@@ -576,6 +576,18 @@ UsbBotGetMaxLun (
                             1,
                             &Result
                             );
+  if (EFI_ERROR (Status) || *MaxLun > USB_BOT_MAX_LUN) {
+    //
+    // If the Get LUN request returns an error or the MaxLun is larger than
+    // the maximum LUN value (0x0f) supported by the USB Mass Storage Class
+    // Bulk-Only Transport Spec, then set MaxLun to 0.
+    //
+    // This improves compatibility with USB FLASH drives that have a single LUN
+    // and either do not return a max LUN value or return an invalid maximum LUN
+    // value.
+    //
+    *MaxLun = 0;
+  }
 
   return Status;
 }
-- 
2.14.2.windows.3