Fix heap buffer overflow in CPDF_SampledFunc::v_Call

This issue was caused by integer overflow in CPDF_SampledFunc::v_Call.
The root cause of this issue is that the content in the test pdf file
was damaged. The solution is to check whether an integer is overflow
before using it.

BUG=452455
R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/886953002

1 files changed, 23 insertions, 4 deletions

diff --git a/core/src/fpdfapi/fpdf_page/fpdf_page_func.cpp b/core/src/fpdfapi/fpdf_page/fpdf_page_func.cpp
index 649bd54a33..3ceb0f7e8b 100644
--- a/core/src/fpdfapi/fpdf_page/fpdf_page_func.cpp
+++ b/core/src/fpdfapi/fpdf_page/fpdf_page_func.cpp
@@ -6,6 +6,7 @@
 
 #include "../../../include/fpdfapi/fpdf_page.h"
 #include "../../../include/fpdfapi/fpdf_module.h"
+#include "../../../third_party/numerics/safe_conversions_impl.h"
 #include "pageint.h"
 #include <limits.h>
 class CPDF_PSEngine;
@@ -553,13 +554,24 @@ FX_BOOL CPDF_SampledFunc::v_Call(FX_FLOAT* inputs, FX_FLOAT* results) const
         }
         pos += index[i] * blocksize[i];
     }
-    int bitpos = pos * m_nBitsPerSample * m_nOutputs;
+    FX_SAFE_INT32 bitpos = pos;
+    bitpos *= m_nBitsPerSample;
+    bitpos *= m_nOutputs;
+    if (!bitpos.IsValid()) {
+        return FALSE;
+    }
     FX_LPCBYTE pSampleData = m_pSampleStream->GetData();
     if (pSampleData == NULL) {
         return FALSE;
     }
+    FX_SAFE_INT32 bitpos1 = m_nOutputs - 1 > 0 ? m_nOutputs - 1 : 0; 
+    bitpos1 *= m_nBitsPerSample;
+    bitpos1 += bitpos.ValueOrDie();
+    if (!bitpos1.IsValid()) {
+        return FALSE;
+    }
     for (int j = 0; j < m_nOutputs; j ++) {
-        FX_DWORD sample = _GetBits32(pSampleData, bitpos + j * m_nBitsPerSample, m_nBitsPerSample);
+        FX_DWORD sample = _GetBits32(pSampleData, bitpos.ValueOrDie() + j * m_nBitsPerSample, m_nBitsPerSample);
         FX_FLOAT encoded = (FX_FLOAT)sample;
         for (int i = 0; i < m_nInputs; i ++) {
             if (index[i] == m_pEncodeInfo[i].sizes - 1) {
@@ -567,8 +579,15 @@ FX_BOOL CPDF_SampledFunc::v_Call(FX_FLOAT* inputs, FX_FLOAT* results) const
                     encoded = encoded_input[i] * (FX_FLOAT)sample;
                 }
             } else {
-                int bitpos1 = bitpos + m_nBitsPerSample * m_nOutputs * blocksize[i];
-                FX_DWORD sample1 = _GetBits32(pSampleData, bitpos1 + j * m_nBitsPerSample, m_nBitsPerSample);
+                FX_SAFE_INT32 bitpos2 = blocksize[i];
+                bitpos2 += 1;
+                bitpos2 *= m_nBitsPerSample; 
+                bitpos2 *= m_nOutputs;
+                bitpos2 += bitpos.ValueOrDie();
+                if (!bitpos2.IsValid()) {
+                    return FALSE;
+                }
+                FX_DWORD sample1 = _GetBits32(pSampleData, bitpos2.ValueOrDie(), m_nBitsPerSample);
                 encoded += (encoded_input[i] - index[i]) * ((FX_FLOAT)sample1 - (FX_FLOAT)sample);
             }
         }