From 1bb6b7acddc7dfe0c8b5fc566cafd555d971613a Mon Sep 17 00:00:00 2001
From: Jeff Young <jeff@rokeby.ie>
Date: Fri, 3 Mar 2023 12:53:22 +0000
Subject: [PATCH] Overflow safety.

Potential fix for some or all of
https://gitlab.com/kicad/code/kicad/-/issues/13969

(cherry picked from commit 2f2a00c30743d48d0e2eed46e38dcf8b3081142f)
---
 libs/kimath/include/math/vector2d.h | 28 ++++++++++++++++++++++++---
 libs/kimath/src/geometry/seg.cpp    | 30 +++++++++++++++++++----------
 2 files changed, 45 insertions(+), 13 deletions(-)

diff --git a/libs/kimath/include/math/vector2d.h b/libs/kimath/include/math/vector2d.h
index 79a804e714..e57cbbb3c4 100644
--- a/libs/kimath/include/math/vector2d.h
+++ b/libs/kimath/include/math/vector2d.h
@@ -99,8 +99,19 @@ public:
     template <typename CastingType>
     VECTOR2( const VECTOR2<CastingType>& aVec )
     {
-        x = (T) aVec.x;
-        y = (T) aVec.y;
+        if( std::is_same<T, int>::value )
+        {
+            CastingType minI = static_cast<CastingType>( std::numeric_limits<int>::min() );
+            CastingType maxI = static_cast<CastingType>( std::numeric_limits<int>::max() );
+
+            x = static_cast<int>( std::max( minI, std::min( aVec.x, maxI ) ) );
+            y = static_cast<int>( std::max( minI, std::min( aVec.y, maxI ) ) );
+        }
+        else
+        {
+            x = static_cast<T>( aVec.x );
+            y = static_cast<T>( aVec.y );
+        }
     }
 
     /// Copy a vector
@@ -114,7 +125,18 @@ public:
     template <typename CastedType>
     VECTOR2<CastedType> operator()() const
     {
-        return VECTOR2<CastedType>( (CastedType) x, (CastedType) y );
+        if( std::is_same<CastedType, int>::value )
+        {
+            T minI = static_cast<T>( std::numeric_limits<int>::min() );
+            T maxI = static_cast<T>( std::numeric_limits<int>::max() );
+
+            return VECTOR2<int>( static_cast<int>( std::max( minI, std::min( x, maxI ) ) ),
+                                 static_cast<int>( std::max( minI, std::min( y, maxI ) ) ) );
+        }
+        else
+        {
+            return VECTOR2<CastedType>( static_cast<CastedType>( x ), static_cast<CastedType>( y ) );
+        }
     }
 
     /**
diff --git a/libs/kimath/src/geometry/seg.cpp b/libs/kimath/src/geometry/seg.cpp
index 37e2ab3006..f94f4b366f 100644
--- a/libs/kimath/src/geometry/seg.cpp
+++ b/libs/kimath/src/geometry/seg.cpp
@@ -171,8 +171,16 @@ bool SEG::intersects( const SEG& aSeg, bool aIgnoreEndpoints, bool aLines, VECTO
 
     if( aPt )
     {
-        *aPt = VECTOR2I( aSeg.A.x + rescale( q, (ecoord) f.x, d ),
-                         aSeg.A.y + rescale( q, (ecoord) f.y, d ) );
+        VECTOR2<ecoord> result( aSeg.A.x + rescale( q, (ecoord) f.x, d ),
+                                aSeg.A.y + rescale( q, (ecoord) f.y, d ) );
+
+        if( abs( result.x ) >= std::numeric_limits<VECTOR2I::coord_type>::max()
+            || abs( result.y ) >= std::numeric_limits<VECTOR2I::coord_type>::max() )
+        {
+            return false;
+        }
+
+        *aPt = VECTOR2I( (int) result.x, (int) result.y );
     }
 
     return true;
@@ -273,10 +281,10 @@ const VECTOR2I SEG::NearestPoint( const VECTOR2I& aP ) const
     else if( t > l_squared )
         return B;
 
-    int xp = rescale( t, (ecoord) d.x, l_squared );
-    int yp = rescale( t, (ecoord) d.y, l_squared );
+    ecoord xp = rescale( t, (ecoord) d.x, l_squared );
+    ecoord yp = rescale( t, (ecoord) d.y, l_squared );
 
-    return A + VECTOR2I( xp, yp );
+    return VECTOR2<ecoord>( A.x + xp, A.y + yp );
 }
 
 
@@ -285,17 +293,19 @@ const VECTOR2I SEG::ReflectPoint( const VECTOR2I& aP ) const
     VECTOR2I                d = B - A;
     VECTOR2I::extended_type l_squared = d.Dot( d );
     VECTOR2I::extended_type t = d.Dot( aP - A );
-    VECTOR2I                c;
+    VECTOR2<ecoord>         c;
 
     if( !l_squared )
+    {
         c = aP;
+    }
     else
     {
         c.x = A.x + rescale( t, static_cast<VECTOR2I::extended_type>( d.x ), l_squared );
         c.y = A.y + rescale( t, static_cast<VECTOR2I::extended_type>( d.y ), l_squared );
     }
 
-    return 2 * c - aP;
+    return VECTOR2<ecoord>( 2 * c.x - aP.x, 2 * c.y - aP.y );
 }
 
 
@@ -309,10 +319,10 @@ VECTOR2I SEG::LineProject( const VECTOR2I& aP ) const
 
     ecoord t = d.Dot( aP - A );
 
-    int xp = rescale( t, ecoord{ d.x }, l_squared );
-    int yp = rescale( t, ecoord{ d.y }, l_squared );
+    ecoord xp = rescale( t, ecoord{ d.x }, l_squared );
+    ecoord yp = rescale( t, ecoord{ d.y }, l_squared );
 
-    return A + VECTOR2I( xp, yp );
+    return VECTOR2<ecoord>( A.x + xp, A.y + yp );
 }