From 3a57378f15d8bbea48b9be13c09bacb6180843e7 Mon Sep 17 00:00:00 2001
From: N <71219152+PokeCodec@users.noreply.github.com>
Date: Tue, 10 Nov 2020 21:20:58 -0500
Subject: [PATCH] Fix potential over/underflow as noted by "TODO:" comment
 (#8081)

Fixed potential errors caused by overflow or underfow in
SectionInput.cpp

## PR Checklist
* [x] CLA signed
* [x] Tests added/passed

## Detailed Description of the Pull Request / Additional comments
In selectionInput.cpp, there is both a potential overflow and potential
underflow. To address this issue, I casted the calculation up to int,
which is then checked because of integer promotion. Underflow and
underflow is therefore impossible because now if the calculation exceeds
SHORT_MAX, it will have exceeded bufferSize.BottomInclusive() or
bufferSize.Top() anyway, and be set to them.

## Validation Steps Performed
Passed Unit Testing
Manual Validation
---
 src/host/selectionInput.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/host/selectionInput.cpp b/src/host/selectionInput.cpp
index 4ec415dd516..f551b346c10 100644
--- a/src/host/selectionInput.cpp
+++ b/src/host/selectionInput.cpp
@@ -390,7 +390,7 @@ bool Selection::HandleKeyboardLineSelectionEvent(const INPUT_KEY_INFO* const pIn
             // shift + pgup/pgdn extends selection up or down one full screen
         case VK_NEXT:
         {
-            coordSelPoint.Y += sWindowHeight; // TODO: potential overflow
+            coordSelPoint.Y = base::CheckAdd(coordSelPoint.Y, sWindowHeight).ValueOrDefault(bufferSize.BottomInclusive());
             if (coordSelPoint.Y > bufferSize.BottomInclusive())
             {
                 coordSelPoint.Y = bufferSize.BottomInclusive();
@@ -399,7 +399,7 @@ bool Selection::HandleKeyboardLineSelectionEvent(const INPUT_KEY_INFO* const pIn
         }
         case VK_PRIOR:
         {
-            coordSelPoint.Y -= sWindowHeight; // TODO: potential underflow
+            coordSelPoint.Y = base::CheckSub(coordSelPoint.Y, sWindowHeight).ValueOrDefault(bufferSize.Top());
             if (coordSelPoint.Y < bufferSize.Top())
             {
                 coordSelPoint.Y = bufferSize.Top();