Add printing::CreateReadOnlySharedMemoryRegionWithData().

Consolidate non-trivial, repeated code that creates shared memory
regions inside sandboxed environments.

Change-Id: I29e0715a9d43fdde030ee0a2286f872b34576c8f
Reviewed-on: https://chromium-review.googlesource.com/1056393
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Ken Rockot <rockot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#560783}

chrome/services/printing/pdf_to_emf_converter.cc

@@ -10,7 +10,7 @@
 
 #include "base/lazy_instance.h"
 #include "base/stl_util.h"
-#include "mojo/public/cpp/system/platform_handle.h"
+#include "components/printing/service/public/cpp/pdf_service_mojo_utils.h"
 #include "pdf/pdf.h"
 #include "printing/emf_win.h"
 #include "ui/gfx/gdi_util.h"
@@ -163,22 +163,16 @@ base::ReadOnlySharedMemoryRegion PdfToEmfConverter::RenderPdfPageToMetafile(
   metafile.FinishPage();
   metafile.FinishDocument();
 
-  mojo::ScopedSharedBufferHandle emf_handle =
-      mojo::SharedBufferHandle::Create(metafile.GetDataSize());
-  mojo::ScopedSharedBufferHandle readonly_handle;
-  if (emf_handle.is_valid()) {
-    mojo::ScopedSharedBufferMapping emf_mapping =
-        emf_handle->Map(metafile.GetDataSize());
-    if (emf_mapping &&
-        metafile.GetData(emf_mapping.get(), metafile.GetDataSize())) {
-      readonly_handle =
-          emf_handle->Clone(mojo::SharedBufferHandle::AccessMode::READ_ONLY);
-    }
-  }
-  if (!readonly_handle.is_valid())
+  const uint32_t size = metafile.GetDataSize();
+  base::MappedReadOnlyRegion region_mapping =
+      CreateReadOnlySharedMemoryRegion(size);
+  if (!region_mapping.region.IsValid() || !region_mapping.mapping.IsValid())
+    return invalid_emf_region;
+
+  if (!metafile.GetData(region_mapping.mapping.memory(), size))
     return invalid_emf_region;
 
-  return mojo::UnwrapReadOnlySharedMemoryRegion(std::move(readonly_handle));
+  return std::move(region_mapping.region);
 }
 
 void PdfToEmfConverter::ConvertPage(uint32_t page_number,

chrome/services/printing/pdf_to_pwg_raster_converter.cc

@@ -8,10 +8,10 @@
 #include <string>
 #include <utility>
 
+#include "components/printing/service/public/cpp/pdf_service_mojo_utils.h"
 #include "components/pwg_encoder/bitmap_image.h"
 #include "components/pwg_encoder/pwg_encoder.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
-#include "mojo/public/cpp/system/platform_handle.h"
 #include "pdf/pdf.h"
 #include "printing/pdf_render_settings.h"
 
@@ -96,22 +96,13 @@ base::ReadOnlySharedMemoryRegion RenderPdfPagesToPwgRaster(
     pwg_data += pwg_page;
   }
 
-  mojo::ScopedSharedBufferHandle pwg_handle =
-      mojo::SharedBufferHandle::Create(pwg_data.size());
-  mojo::ScopedSharedBufferHandle readonly_handle;
-  if (pwg_handle.is_valid()) {
-    mojo::ScopedSharedBufferMapping pwg_mapping =
-        pwg_handle->Map(pwg_data.size());
-    if (pwg_mapping) {
-      memcpy(pwg_mapping.get(), pwg_data.data(), pwg_data.size());
-      readonly_handle =
-          pwg_handle->Clone(mojo::SharedBufferHandle::AccessMode::READ_ONLY);
-    }
-  }
-  if (!readonly_handle.is_valid())
+  base::MappedReadOnlyRegion region_mapping =
+      CreateReadOnlySharedMemoryRegion(pwg_data.size());
+  if (!region_mapping.region.IsValid() || !region_mapping.mapping.IsValid())
     return invalid_pwg_region;
 
-  return mojo::UnwrapReadOnlySharedMemoryRegion(std::move(readonly_handle));
+  memcpy(region_mapping.mapping.memory(), pwg_data.data(), pwg_data.size());
+  return std::move(region_mapping.region);
 }
 
 }  // namespace

components/printing/service/pdf_compositor_impl.cc

@@ -228,24 +228,15 @@ mojom::PdfCompositor::Status PdfCompositorImpl::CompositeToPdf(
   }
   doc->close();
 
-  const size_t size = wstream.bytesWritten();
-  mojo::ScopedSharedBufferHandle handle =
-      mojo::SharedBufferHandle::Create(size);
-  mojo::ScopedSharedBufferHandle readonly_handle;
-  if (handle.is_valid()) {
-    mojo::ScopedSharedBufferMapping mapping = handle->Map(size);
-    if (mapping) {
-      wstream.copyToAndReset(mapping.get());
-      readonly_handle =
-          handle->Clone(mojo::SharedBufferHandle::AccessMode::READ_ONLY);
-    }
-  }
-  if (!readonly_handle.is_valid()) {
+  base::MappedReadOnlyRegion region_mapping =
+      CreateReadOnlySharedMemoryRegion(wstream.bytesWritten());
+  if (!region_mapping.region.IsValid() || !region_mapping.mapping.IsValid()) {
     DLOG(ERROR) << "CompositeToPdf: Cannot create new shared memory region.";
     return mojom::PdfCompositor::Status::HANDLE_MAP_ERROR;
   }
 
-  *region = mojo::UnwrapReadOnlySharedMemoryRegion(std::move(readonly_handle));
+  wstream.copyToAndReset(region_mapping.mapping.memory());
+  *region = std::move(region_mapping.region);
   return mojom::PdfCompositor::Status::SUCCESS;
 }
 

components/printing/service/public/cpp/pdf_service_mojo_utils.cc

@@ -7,10 +7,26 @@
 #include <utility>
 
 #include "base/memory/shared_memory.h"
+#include "base/memory/writable_shared_memory_region.h"
 #include "mojo/public/cpp/system/platform_handle.h"
 
 namespace printing {
 
+base::MappedReadOnlyRegion CreateReadOnlySharedMemoryRegion(size_t size) {
+  mojo::ScopedSharedBufferHandle handle =
+      mojo::SharedBufferHandle::Create(size);
+  base::WritableSharedMemoryRegion writable_region =
+      UnwrapWritableSharedMemoryRegion(std::move(handle));
+  base::WritableSharedMemoryMapping mapping = writable_region.Map();
+  if (!mapping.IsValid())
+    return {};
+
+  base::ReadOnlySharedMemoryRegion readonly_region =
+      base::WritableSharedMemoryRegion::ConvertToReadOnly(
+          std::move(writable_region));
+  return {std::move(readonly_region), std::move(mapping)};
+}
+
 std::unique_ptr<base::SharedMemory> GetShmFromMojoHandle(
     mojo::ScopedSharedBufferHandle handle) {
   base::SharedMemoryHandle memory_handle;

components/printing/service/public/cpp/pdf_service_mojo_utils.h

@@ -7,6 +7,7 @@
 
 #include <memory>
 
+#include "base/memory/read_only_shared_memory_region.h"
 #include "mojo/public/cpp/system/buffer.h"
 
 namespace base {
@@ -15,6 +16,10 @@ class SharedMemory;
 
 namespace printing {
 
+// Similar to base::ReadOnlySharedMemoryRegion::Create(), except it works inside
+// sandboxed environments.
+base::MappedReadOnlyRegion CreateReadOnlySharedMemoryRegion(size_t size);
+
 std::unique_ptr<base::SharedMemory> GetShmFromMojoHandle(
     mojo::ScopedSharedBufferHandle handle);