From 878478116ab65646cddc4e590f2440f8aefca19c Mon Sep 17 00:00:00 2001
From: Sami Mujawar <sami.mujawar@arm.com>
Date: Tue, 9 Jul 2019 13:54:04 +0100
Subject: [PATCH] DynamicTablesPkg: Fix GT Block length assignment

The VS2017 compiler reports 'warning C4267: '=': conversion from
'size_t' to 'UINT16', possible loss of data'.

The sizeof() operator is used to calculate the size of the
GT Block structure. The length field in the GT Block structure
is 16-bit wide. Since the return type of sizeof() operator
is size_t the VS2017 compiler reports the above warning.

To fix the warning, an explicit type cast is added. An additional
check is also performed to ensure that the calculated GT Block
length does not exceed MAX_UINT16.

Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
---
 .../Acpi/Arm/AcpiGtdtLibArm/GtdtGenerator.c   | 25 ++++++++++++++++---
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/DynamicTablesPkg/Library/Acpi/Arm/AcpiGtdtLibArm/GtdtGenerator.c b/DynamicTablesPkg/Library/Acpi/Arm/AcpiGtdtLibArm/GtdtGenerator.c
index 7e86c30649..0e99669888 100644
--- a/DynamicTablesPkg/Library/Acpi/Arm/AcpiGtdtLibArm/GtdtGenerator.c
+++ b/DynamicTablesPkg/Library/Acpi/Arm/AcpiGtdtLibArm/GtdtGenerator.c
@@ -350,6 +350,7 @@ AddGTBlockList (
   EFI_ACPI_6_3_GTDT_GT_BLOCK_TIMER_STRUCTURE  * GtBlockFrame;
   CM_ARM_GTBLOCK_TIMER_FRAME_INFO             * GTBlockTimerFrameList;
   UINT32                                        GTBlockTimerFrameCount;
+  UINTN                                         Length;
 
   ASSERT (Gtdt != NULL);
   ASSERT (GTBlockInfo != NULL);
@@ -376,11 +377,27 @@ AddGTBlockList (
       return Status;
     }
 
-    GTBlock->Type = EFI_ACPI_6_3_GTDT_GT_BLOCK;
-    GTBlock->Length = sizeof (EFI_ACPI_6_3_GTDT_GT_BLOCK_STRUCTURE) +
-                        (sizeof (EFI_ACPI_6_3_GTDT_GT_BLOCK_TIMER_STRUCTURE) *
-                          GTBlockInfo->GTBlockTimerFrameCount);
+    Length = sizeof (EFI_ACPI_6_3_GTDT_GT_BLOCK_STRUCTURE) +
+               (sizeof (EFI_ACPI_6_3_GTDT_GT_BLOCK_TIMER_STRUCTURE) *
+                GTBlockInfo->GTBlockTimerFrameCount);
 
+    // Check that the length of the GT block does not
+    // exceed MAX_UINT16
+    if (Length > MAX_UINT16) {
+      Status = EFI_INVALID_PARAMETER;
+      DEBUG ((
+        DEBUG_ERROR,
+        "ERROR: GTDT: Too many GT Frames. Count = %d. " \
+        "Maximum supported GT Block size exceeded. " \
+        "Status = %r\n",
+        GTBlockInfo->GTBlockTimerFrameCount,
+        Status
+        ));
+      return Status;
+    }
+
+    GTBlock->Type = EFI_ACPI_6_3_GTDT_GT_BLOCK;
+    GTBlock->Length = (UINT16)Length;
     GTBlock->Reserved = EFI_ACPI_RESERVED_BYTE;
     GTBlock->CntCtlBase = GTBlockInfo->GTBlockPhysicalAddress;
     GTBlock->GTBlockTimerCount = GTBlockInfo->GTBlockTimerFrameCount;