Read Disk does a modification of ExtMbrStartingLba with the code MultU64x32

(ExtMbrStartingLba, BlockSize) Error detection to see if ExtMbrStartingLBA

has a value of 0. This is invalid as LBA 0 = MBR. After modification, the

next time ExtMbrStartingLba is in this function if ExtMbrStartingLba is set

to 0 in the MBR it never passes the while/do evaluation It is multiplied by 0

by read disk , set to 0 by an invalid MBR and goes back to evaluation This

condition will also cause Ws19 and WS22 to hang, however Microsoft has

developed a hotfix patch that will be released in 2022

 

Date:      Wed Jan 5 12:27:46 2022 -0600

 

On branch graceful_handle_mbr_hang_edit1

Changes to be committed:

        modified:   MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c

---

MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c | 6 ++++++

1 file changed, 6 insertions(+)

 

diff --git a/MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c b/MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c

index 0f8dc5486521..ad18840e5efd 100644

--- a/MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c

+++ b/MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c

@@ -293,6 +293,12 @@ PartitionInstallMbrChildHandles (

           (Mbr->Partition[0].OSIndicator == EXTENDED_WINDOWS_PARTITION))

       {

         ExtMbrStartingLba = UNPACK_UINT32 (Mbr->Partition[0].StartingLBA);

+          //

+          // A value of 0 is invalid for StartingLBA

+          //

+          if (ExtMbrStartingLba == 0) {

+            break;

+          }

         continue;

       }

 

--

2.32.0.windows.1