Fix dangling reference in CFX_CodecMemory.

Do this by making CFX_CodecMemory actually own the memory that
it is ref-counting. Remove some test cases that are now prohibited,
and relax one lifetime restriction in the test because we are now
doing one additional copy (in the test, but not in real life).

Bug:879512
Change-Id: If030dfcf97fe40155c46a42288fc73192437ce9c
Reviewed-on: https://pdfium-review.googlesource.com/c/43670
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>

5 files changed, 74 insertions, 90 deletions

diff --git a/core/fxcodec/codec/ccodec_progressivedecoder.cpp b/core/fxcodec/codec/ccodec_progressivedecoder.cpp
index 07665c1d4a..9d375cbcf1 100644
--- a/core/fxcodec/codec/ccodec_progressivedecoder.cpp
+++ b/core/fxcodec/codec/ccodec_progressivedecoder.cpp
@@ -718,10 +718,7 @@ bool CCodec_ProgressiveDecoder::BmpDetectImageTypeInBuffer(
 
   std::unique_ptr<CodecModuleIface::Context> pBmpContext =
       pBmpModule->Start(this);
-  pBmpModule->Input(pBmpContext.get(),
-                    pdfium::MakeRetain<CFX_CodecMemory>(
-                        pdfium::make_span(m_pSrcBuf.get(), m_SrcSize)),
-                    nullptr);
+  pBmpModule->Input(pBmpContext.get(), m_pCodecMemory, nullptr);
 
   std::vector<uint32_t> palette;
   int32_t readResult = pBmpModule->ReadHeader(
@@ -866,10 +863,7 @@ bool CCodec_ProgressiveDecoder::GifDetectImageTypeInBuffer(
     return false;
   }
   m_pGifContext = pGifModule->Start(this);
-  pGifModule->Input(m_pGifContext.get(),
-                    pdfium::MakeRetain<CFX_CodecMemory>(
-                        pdfium::make_span(m_pSrcBuf.get(), m_SrcSize)),
-                    nullptr);
+  pGifModule->Input(m_pGifContext.get(), m_pCodecMemory, nullptr);
   m_SrcComponents = 1;
   CFX_GifDecodeStatus readResult = pGifModule->ReadHeader(
       m_pGifContext.get(), &m_SrcWidth, &m_SrcHeight, &m_GifPltNumber,
@@ -1052,10 +1046,8 @@ bool CCodec_ProgressiveDecoder::JpegDetectImageTypeInBuffer(
     m_status = FXCODEC_STATUS_ERR_MEMORY;
     return false;
   }
-  pJpegModule->Input(m_pJpegContext.get(),
-                     pdfium::MakeRetain<CFX_CodecMemory>(
-                         pdfium::make_span(m_pSrcBuf.get(), m_SrcSize)),
-                     nullptr);
+  pJpegModule->Input(m_pJpegContext.get(), m_pCodecMemory, nullptr);
+
   // Setting jump marker before calling ReadHeader, since a longjmp to
   // the marker indicates a fatal error.
   if (setjmp(*pJpegModule->GetJumpMark(m_pJpegContext.get())) == -1) {
@@ -1264,12 +1256,7 @@ bool CCodec_ProgressiveDecoder::PngDetectImageTypeInBuffer(
     m_status = FXCODEC_STATUS_ERR_MEMORY;
     return false;
   }
-  bool bResult =
-      pPngModule->Input(m_pPngContext.get(),
-                        pdfium::MakeRetain<CFX_CodecMemory>(
-                            pdfium::make_span(m_pSrcBuf.get(), m_SrcSize)),
-                        pAttribute);
-  while (bResult) {
+  while (pPngModule->Input(m_pPngContext.get(), m_pCodecMemory, pAttribute)) {
     uint32_t remain_size = static_cast<uint32_t>(m_pFile->GetSize()) - m_offSet;
     uint32_t input_size =
         remain_size > FXCODEC_BLOCK_SIZE ? FXCODEC_BLOCK_SIZE : remain_size;
@@ -1278,21 +1265,16 @@ bool CCodec_ProgressiveDecoder::PngDetectImageTypeInBuffer(
       m_status = FXCODEC_STATUS_ERR_FORMAT;
       return false;
     }
-    if (m_pSrcBuf && input_size > m_SrcSize) {
-      m_pSrcBuf.reset(FX_Alloc(uint8_t, input_size));
+    if (m_pCodecMemory && input_size > m_SrcSize) {
+      m_pCodecMemory = pdfium::MakeRetain<CFX_CodecMemory>(input_size);
       m_SrcSize = input_size;
     }
-    bResult = m_pFile->ReadBlock(m_pSrcBuf.get(), m_offSet, input_size);
-    if (!bResult) {
+    if (!m_pFile->ReadBlock(m_pCodecMemory->GetBuffer(), m_offSet,
+                            input_size)) {
       m_status = FXCODEC_STATUS_ERR_READ;
       return false;
     }
     m_offSet += input_size;
-    bResult =
-        pPngModule->Input(m_pPngContext.get(),
-                          pdfium::MakeRetain<CFX_CodecMemory>(
-                              pdfium::make_span(m_pSrcBuf.get(), input_size)),
-                          pAttribute);
   }
   m_pPngContext.reset();
   if (m_SrcPassNumber == 0) {
@@ -1367,11 +1349,12 @@ FXCODEC_STATUS CCodec_ProgressiveDecoder::PngContinueDecode() {
       m_status = FXCODEC_STATUS_DECODE_FINISH;
       return m_status;
     }
-    if (m_pSrcBuf && input_size > m_SrcSize) {
-      m_pSrcBuf.reset(FX_Alloc(uint8_t, input_size));
+    if (m_pCodecMemory && input_size > m_SrcSize) {
+      m_pCodecMemory = pdfium::MakeRetain<CFX_CodecMemory>(input_size);
       m_SrcSize = input_size;
     }
-    bool bResult = m_pFile->ReadBlock(m_pSrcBuf.get(), m_offSet, input_size);
+    bool bResult =
+        m_pFile->ReadBlock(m_pCodecMemory->GetBuffer(), m_offSet, input_size);
     if (!bResult) {
       m_pDeviceBitmap = nullptr;
       m_pFile = nullptr;
@@ -1379,11 +1362,7 @@ FXCODEC_STATUS CCodec_ProgressiveDecoder::PngContinueDecode() {
       return m_status;
     }
     m_offSet += input_size;
-    bResult =
-        pPngModule->Input(m_pPngContext.get(),
-                          pdfium::MakeRetain<CFX_CodecMemory>(
-                              pdfium::make_span(m_pSrcBuf.get(), input_size)),
-                          nullptr);
+    bResult = pPngModule->Input(m_pPngContext.get(), m_pCodecMemory, nullptr);
     if (!bResult) {
       m_pDeviceBitmap = nullptr;
       m_pFile = nullptr;
@@ -1570,10 +1549,9 @@ bool CCodec_ProgressiveDecoder::DetectImageType(FXCODEC_IMAGE_TYPE imageType,
 
   size_t size = std::min<size_t>(m_pFile->GetSize(), FXCODEC_BLOCK_SIZE);
   m_SrcSize = static_cast<uint32_t>(size);
-  m_pSrcBuf.reset(FX_Alloc(uint8_t, m_SrcSize));
-
+  m_pCodecMemory = pdfium::MakeRetain<CFX_CodecMemory>(m_SrcSize);
   m_offSet = 0;
-  if (!m_pFile->ReadBlock(m_pSrcBuf.get(), m_offSet, m_SrcSize)) {
+  if (!m_pFile->ReadBlock(m_pCodecMemory->GetBuffer(), m_offSet, m_SrcSize)) {
     m_status = FXCODEC_STATUS_ERR_READ;
     return false;
   }
@@ -1629,31 +1607,26 @@ bool CCodec_ProgressiveDecoder::ReadMoreData(
     dwBytesToFetchFromFile =
         std::min<uint32_t>(dwBytesToFetchFromFile, FXCODEC_BLOCK_SIZE);
     uint32_t dwNewSize = m_SrcSize + dwBytesToFetchFromFile;
-    uint8_t* pNewBuf = FX_TryRealloc(uint8_t, m_pSrcBuf.release(), dwNewSize);
-    if (!pNewBuf) {
+    if (!m_pCodecMemory->TryResize(dwNewSize)) {
       err_status = FXCODEC_STATUS_ERR_MEMORY;
       return false;
     }
     m_SrcSize = dwNewSize;
-    m_pSrcBuf.reset(pNewBuf);
   } else {
     uint32_t dwConsumed = m_SrcSize - dwUnconsumed;
-    memmove(m_pSrcBuf.get(), m_pSrcBuf.get() + dwConsumed, dwUnconsumed);
+    m_pCodecMemory->Consume(dwConsumed);
     dwBytesToFetchFromFile = std::min(dwBytesToFetchFromFile, dwConsumed);
     m_SrcSize = dwBytesToFetchFromFile + dwUnconsumed;
   }
 
   // Append new data past the bytes not yet processed by the codec.
-  if (!m_pFile->ReadBlock(m_pSrcBuf.get() + dwUnconsumed, m_offSet,
+  if (!m_pFile->ReadBlock(m_pCodecMemory->GetBuffer() + dwUnconsumed, m_offSet,
                           dwBytesToFetchFromFile)) {
     err_status = FXCODEC_STATUS_ERR_READ;
     return false;
   }
   m_offSet += dwBytesToFetchFromFile;
-  return pModule->Input(pContext,
-                        pdfium::MakeRetain<CFX_CodecMemory>(
-                            pdfium::make_span(m_pSrcBuf.get(), m_SrcSize)),
-                        nullptr);
+  return pModule->Input(pContext, m_pCodecMemory, nullptr);
 }
 
 FXCODEC_STATUS CCodec_ProgressiveDecoder::LoadImageInfo(
diff --git a/core/fxcodec/codec/ccodec_progressivedecoder.h b/core/fxcodec/codec/ccodec_progressivedecoder.h
index 9821c67f4f..d0419f8268 100644
--- a/core/fxcodec/codec/ccodec_progressivedecoder.h
+++ b/core/fxcodec/codec/ccodec_progressivedecoder.h
@@ -251,8 +251,7 @@ class CCodec_ProgressiveDecoder :
   RetainPtr<IFX_SeekableReadStream> m_pFile;
   RetainPtr<CFX_DIBitmap> m_pDeviceBitmap;
   UnownedPtr<CCodec_ModuleMgr> m_pCodecMgr;
-  // |m_pSrcBuf| must outlive |m_pGifContext|.
-  std::unique_ptr<uint8_t, FxFreeDeleter> m_pSrcBuf;
+  RetainPtr<CFX_CodecMemory> m_pCodecMemory;
   std::unique_ptr<uint8_t, FxFreeDeleter> m_pDecodeBuf;
   std::unique_ptr<FX_ARGB, FxFreeDeleter> m_pSrcPalette;
   std::unique_ptr<CodecModuleIface::Context> m_pJpegContext;
diff --git a/core/fxcodec/codec/cfx_codec_memory.cpp b/core/fxcodec/codec/cfx_codec_memory.cpp
index b8cf97b098..640db12415 100644
--- a/core/fxcodec/codec/cfx_codec_memory.cpp
+++ b/core/fxcodec/codec/cfx_codec_memory.cpp
@@ -6,13 +6,13 @@
 
 #include <algorithm>
 
-CFX_CodecMemory::CFX_CodecMemory(pdfium::span<uint8_t> buffer)
-    : buffer_(buffer) {}
+CFX_CodecMemory::CFX_CodecMemory(size_t buffer_size)
+    : buffer_(FX_Alloc(uint8_t, buffer_size)), size_(buffer_size) {}
 
 CFX_CodecMemory::~CFX_CodecMemory() = default;
 
 bool CFX_CodecMemory::Seek(size_t pos) {
-  if (pos > buffer_.size())
+  if (pos > size_)
     return false;
 
   pos_ = pos;
@@ -23,8 +23,25 @@ size_t CFX_CodecMemory::ReadBlock(void* buffer, size_t size) {
   if (!buffer || !size || IsEOF())
     return 0;
 
-  size_t bytes_to_read = std::min(size, buffer_.size() - pos_);
-  memcpy(buffer, &buffer_[pos_], bytes_to_read);
+  size_t bytes_to_read = std::min(size, size_ - pos_);
+  memcpy(buffer, buffer_.get() + pos_, bytes_to_read);
   pos_ += bytes_to_read;
   return bytes_to_read;
 }
+
+bool CFX_CodecMemory::TryResize(size_t new_buffer_size) {
+  uint8_t* pOldBuf = buffer_.release();
+  uint8_t* pNewBuf = FX_TryRealloc(uint8_t, pOldBuf, new_buffer_size);
+  if (!pNewBuf) {
+    buffer_.reset(pOldBuf);
+    return false;
+  }
+  buffer_.reset(pNewBuf);
+  size_ = new_buffer_size;
+  return true;
+}
+
+void CFX_CodecMemory::Consume(size_t consumed) {
+  size_t unconsumed = size_ - consumed;
+  memmove(buffer_.get(), buffer_.get() + consumed, unconsumed);
+}
diff --git a/core/fxcodec/codec/cfx_codec_memory.h b/core/fxcodec/codec/cfx_codec_memory.h
index 0d11d41de8..fa26e240ec 100644
--- a/core/fxcodec/codec/cfx_codec_memory.h
+++ b/core/fxcodec/codec/cfx_codec_memory.h
@@ -5,6 +5,9 @@
 #ifndef CORE_FXCODEC_CODEC_CFX_CODEC_MEMORY_H_
 #define CORE_FXCODEC_CODEC_CFX_CODEC_MEMORY_H_
 
+#include <memory>
+
+#include "core/fxcrt/fx_memory.h"
 #include "core/fxcrt/retain_ptr.h"
 #include "third_party/base/span.h"
 
@@ -13,21 +16,28 @@ class CFX_CodecMemory final : public Retainable {
   template <typename T, typename... Args>
   friend RetainPtr<T> pdfium::MakeRetain(Args&&... args);
 
-  pdfium::span<uint8_t> GetSpan() { return buffer_; }
-  uint8_t* GetBuffer() { return buffer_.data(); }
-  size_t GetSize() const { return buffer_.size(); }
+  pdfium::span<uint8_t> GetSpan() { return {buffer_.get(), size_}; }
+  uint8_t* GetBuffer() { return buffer_.get(); }
+  size_t GetSize() const { return size_; }
   size_t GetPosition() const { return pos_; }
-  bool IsEOF() const { return pos_ >= buffer_.size(); }
+  bool IsEOF() const { return pos_ >= size_; }
   size_t ReadBlock(void* buffer, size_t size);
 
   // Sets the cursor position to |pos| if possible.
   bool Seek(size_t pos);
 
+  // Try to change the size of the buffer, keep the old one on failure.
+  bool TryResize(size_t new_buffer_size);
+
+  // Schlep the bytes down the buffer.
+  void Consume(size_t consumed);
+
  private:
-  explicit CFX_CodecMemory(pdfium::span<uint8_t> buffer);
+  explicit CFX_CodecMemory(size_t buffer_size);
   ~CFX_CodecMemory() override;
 
-  pdfium::span<uint8_t> const buffer_;
+  std::unique_ptr<uint8_t, FxFreeDeleter> buffer_;
+  size_t size_ = 0;
   size_t pos_ = 0;
 };
 
diff --git a/core/fxcodec/gif/cfx_gifcontext_unittest.cpp b/core/fxcodec/gif/cfx_gifcontext_unittest.cpp
index 24b8acd769..9b081a4183 100644
--- a/core/fxcodec/gif/cfx_gifcontext_unittest.cpp
+++ b/core/fxcodec/gif/cfx_gifcontext_unittest.cpp
@@ -4,6 +4,8 @@
 
 #include "core/fxcodec/gif/cfx_gifcontext.h"
 
+#include <utility>
+
 #include "testing/gtest/include/gtest/gtest.h"
 
 class CFX_GifContextForTest final : public CFX_GifContext {
@@ -19,49 +21,33 @@ class CFX_GifContextForTest final : public CFX_GifContext {
 
   CFX_CodecMemory* InputBuffer() const { return input_buffer_.Get(); }
   void SetTestInputBuffer(pdfium::span<uint8_t> input) {
-    SetInputBuffer(pdfium::MakeRetain<CFX_CodecMemory>(input));
+    auto pMemory = pdfium::MakeRetain<CFX_CodecMemory>(input.size());
+    memcpy(pMemory->GetBuffer(), input.data(), input.size());
+    SetInputBuffer(std::move(pMemory));
   }
 };
 
 TEST(CFX_GifContext, SetInputBuffer) {
   uint8_t buffer[] = {0x00, 0x01, 0x02};
-  {
-    // Context must not outlive its buffers.
-    CFX_GifContextForTest context(nullptr, nullptr);
-
-    context.SetTestInputBuffer({nullptr, 0});
-    EXPECT_EQ(nullptr, context.InputBuffer()->GetBuffer());
-    EXPECT_EQ(0u, context.InputBuffer()->GetSize());
-    EXPECT_EQ(0u, context.InputBuffer()->GetPosition());
-
-    context.SetTestInputBuffer({nullptr, 100});
-    EXPECT_EQ(nullptr, context.InputBuffer()->GetBuffer());
-    EXPECT_EQ(100u, context.InputBuffer()->GetSize());
-    EXPECT_EQ(0u, context.InputBuffer()->GetPosition());
+  CFX_GifContextForTest context(nullptr, nullptr);
 
-    context.SetTestInputBuffer({buffer, 0});
-    EXPECT_EQ(buffer, context.InputBuffer()->GetBuffer());
-    EXPECT_EQ(0u, context.InputBuffer()->GetSize());
-    EXPECT_EQ(0u, context.InputBuffer()->GetPosition());
+  context.SetTestInputBuffer({nullptr, 0});
+  EXPECT_EQ(0u, context.InputBuffer()->GetSize());
+  EXPECT_EQ(0u, context.InputBuffer()->GetPosition());
 
-    context.SetTestInputBuffer({buffer, 3});
-    EXPECT_EQ(buffer, context.InputBuffer()->GetBuffer());
-    EXPECT_EQ(3u, context.InputBuffer()->GetSize());
-    EXPECT_EQ(0u, context.InputBuffer()->GetPosition());
+  context.SetTestInputBuffer({buffer, 0});
+  EXPECT_EQ(0u, context.InputBuffer()->GetSize());
+  EXPECT_EQ(0u, context.InputBuffer()->GetPosition());
 
-    context.SetTestInputBuffer({buffer, 100});
-    EXPECT_EQ(buffer, context.InputBuffer()->GetBuffer());
-    EXPECT_EQ(100u, context.InputBuffer()->GetSize());
-    EXPECT_EQ(0u, context.InputBuffer()->GetPosition());
-  }
+  context.SetTestInputBuffer({buffer, 3});
+  EXPECT_EQ(3u, context.InputBuffer()->GetSize());
+  EXPECT_EQ(0u, context.InputBuffer()->GetPosition());
 }
 
 TEST(CFX_GifContext, ReadAllOrNone) {
   std::vector<uint8_t> dest_buffer;
   uint8_t src_buffer[] = {0x00, 0x01, 0x02, 0x03, 0x04,
                           0x05, 0x06, 0x07, 0x08, 0x09};
-  {
-    // Context must not outlive its buffers.
     CFX_GifContextForTest context(nullptr, nullptr);
 
     context.SetTestInputBuffer({nullptr, 0});
@@ -94,7 +80,6 @@ TEST(CFX_GifContext, ReadAllOrNone) {
       EXPECT_TRUE(context.ReadAllOrNone(dest_buffer.data(), 1));
       EXPECT_EQ(src_buffer[i], dest_buffer[0]);
     }
-  }
 }
 
 TEST(CFX_GifContext, ReadGifSignature) {