Fix the potential integer overflow from 'offset+size' in extension.h and fpdfview.cpp

core/src/fxcrt/extension.h

Index: core/src/fxcrt/extension.h
diff --git a/core/src/fxcrt/extension.h b/core/src/fxcrt/extension.h
index b8dce7c97d9a5df829dae6fd639a090db9e40972..d04d1da55011a2fd93afb1b25b9adbdbc01d7993 100644
--- a/core/src/fxcrt/extension.h
+++ b/core/src/fxcrt/extension.h
@@ -7,8 +7,6 @@
 #ifndef _FXCRT_EXTENSION_IMP_
 #define _FXCRT_EXTENSION_IMP_
 
-#include "../../../third_party/numerics/safe_math.h"
-
 class IFXCRT_FileAccess
 {
 public:
@@ -68,9 +66,17 @@ public:
     }
     virtual FX_BOOL				SetRange(FX_FILESIZE offset, FX_FILESIZE size)
     {
-        if (offset < 0 || offset + size > m_pFile->GetSize()) {
+        if (offset < 0 || size < 0) {
+            return FALSE;
+        }
+     
+        FX_SAFE_FILESIZE pos = size;
+        pos += offset;
+
+        if (!pos.IsValid() || pos.ValueOrDie() >= m_pFile->GetSize()) {
             return FALSE;
         }
+
         m_nOffset = offset, m_nSize = size;
         m_bUseRange = TRUE;
         m_pFile->SetPosition(m_nOffset);
@@ -82,13 +88,18 @@ public:
     }
     virtual FX_BOOL				ReadBlock(void* buffer, FX_FILESIZE offset, size_t size)
     {
+        if (m_bUseRange && offset < 0) {
+            return FALSE;
+        }
+        FX_SAFE_FILESIZE pos = offset;
+
         if (m_bUseRange) {
-            if (offset + size > (size_t)GetSize()) {
+            pos += m_nOffset;
+            if (!pos.IsValid() || pos.ValueOrDie() >= (size_t)GetSize()) {
                 return FALSE;
             }
-            offset += m_nOffset;
         }
-        return (FX_BOOL)m_pFile->ReadPos(buffer, size, offset);
+        return (FX_BOOL)m_pFile->ReadPos(buffer, size, pos.ValueOrDie());
     }
     virtual size_t				ReadBlock(void* buffer, size_t size)
     {
@@ -184,10 +195,12 @@ public:
     }
     virtual FX_BOOL				SetRange(FX_FILESIZE offset, FX_FILESIZE size)
     {
-        base::CheckedNumeric<FX_FILESIZE> range = size;
-        range += size;
- 
-        if (!range.IsValid() || offset <= 0 || size <= 0 || range.ValueOrDie() > m_nCurSize) {
+        if (offset < 0 || size < 0) {
+            return FALSE;
+        }
+        FX_SAFE_FILESIZE range = size;
+        range += offset;
+        if (!range.IsValid() || range.ValueOrDie() >= m_nCurSize) {
             return FALSE;
         }
         
@@ -206,7 +219,7 @@ public:
             return FALSE;
         }
 
-        base::CheckedNumeric<FX_FILESIZE> safeOffset = offset;
+        FX_SAFE_FILESIZE safeOffset = offset;
         if (m_bUseRange) {
             safeOffset += m_nOffset;
         }
@@ -217,9 +230,9 @@ public:
 
         offset = safeOffset.ValueOrDie();
 
-        base::CheckedNumeric<size_t> newPos = size;
+        FX_SAFE_SIZET newPos = size;
         newPos += offset;
-        if (!newPos.IsValid() || newPos.ValueOrDefault(0) == 0 || newPos.ValueOrDie() > m_nCurSize) {
+        if (!newPos.IsValid() || newPos.ValueOrDefault(0) == 0 || newPos.ValueOrDie() >= m_nCurSize) {
             return FALSE;
         }
 
@@ -269,7 +282,7 @@ public:
             offset += (FX_FILESIZE)m_nOffset;
         }
         if (m_dwFlags & FX_MEMSTREAM_Consecutive) {
-            base::CheckedNumeric<size_t> newPos = size; 
+            FX_SAFE_SIZET newPos = size; 
             newPos += offset;
             if (!newPos.IsValid())
                 return FALSE;
@@ -295,10 +308,11 @@ public:
             return TRUE;
         }
 
-        base::CheckedNumeric<size_t> newPos = size;
+        FX_SAFE_SIZET newPos = size;
         newPos += offset;
-        if (!newPos.IsValid())
+        if (!newPos.IsValid()) {
             return FALSE;
+        }
 
         if (!ExpandBlocks(newPos.ValueOrDie())) {
             return FALSE;