Add a GUID to base::SharedMemoryHandle.

base/memory/shared_memory_win.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/memory/shared_memory.h"
 
 #include <aclapi.h>
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/rand_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/unguessable_token.h"
 
 namespace {
 
 // Errors that can occur during Shared Memory construction.
 // These match tools/metrics/histograms/histograms.xml.
 // This enum is append-only.
 enum CreateError {
   SUCCESS = 0,
   SIZE_ZERO = 1,
   SIZE_TOO_LARGE = 2,
@@ skipping 207 matching lines @@
 
     // Windows ignores DACLs on certain unnamed objects (like shared sections).
     // So, we generate a random name when we need to enforce read-only.
     uint64_t rand_values[4];
     RandBytes(&rand_values, sizeof(rand_values));
     name_ = StringPrintf(L"CrSharedMem_%016llx%016llx%016llx%016llx",
                          rand_values[0], rand_values[1],
                          rand_values[2], rand_values[3]);
   }
   DCHECK(!name_.empty());
-  shm_ = SharedMemoryHandle(CreateFileMappingWithReducedPermissions(
-      &sa, rounded_size, name_.c_str()));
+  shm_ = SharedMemoryHandle(
+      CreateFileMappingWithReducedPermissions(&sa, rounded_size, name_.c_str()),
+      UnguessableToken::Create());
   if (!shm_.IsValid()) {
     // The error is logged within CreateFileMappingWithReducedPermissions().
     return false;
   }
 
   requested_size_ = options.size;
 
   // Check if the shared memory pre-exists.
   if (GetLastError() == ERROR_ALREADY_EXISTS) {
     // If the file already existed, set requested_size_ to 0 to show that
@@ skipping 17 matching lines @@
   return true;
 }
 
 bool SharedMemory::Open(const std::string& name, bool read_only) {
   DCHECK(!shm_.IsValid());
   DWORD access = FILE_MAP_READ | SECTION_QUERY;
   if (!read_only)
     access |= FILE_MAP_WRITE;
   name_ = ASCIIToUTF16(name);
   read_only_ = read_only;
+
+  // This form of sharing shared memory is deprecated. https://crbug.com/345734.
+  // Technically, we should also pass the GUID from the original shared memory
+  // region. Instead, we should just remove all instances of this.

[Nico, 2017/05/05 18:34:36]

Likewise?

What's the failure case if someone calls this function? Just shm memory being
double-counted? Is there anything that prevents new callers of this? Are you
going to work on removing calls to this function – sounds like this isn't really
possible?

[erikchen, 2017/05/05 19:29:33]

Done.

   shm_ = SharedMemoryHandle(
-      OpenFileMapping(access, false, name_.empty() ? nullptr : name_.c_str()));
+      OpenFileMapping(access, false, name_.empty() ? nullptr : name_.c_str()),
+      UnguessableToken::Create());
   if (!shm_.IsValid())
     return false;
   // If a name specified assume it's an external section.
   if (!name_.empty())
     external_section_ = true;
   // Note: size_ is not set in this case.
   return true;
 }
 
 bool SharedMemory::MapAt(off_t offset, size_t bytes) {
@@ skipping 31 matching lines @@
   return true;
 }
 
 SharedMemoryHandle SharedMemory::GetReadOnlyHandle() {
   HANDLE result;
   ProcessHandle process = GetCurrentProcess();
   if (!::DuplicateHandle(process, shm_.GetHandle(), process, &result,
                          FILE_MAP_READ | SECTION_QUERY, FALSE, 0)) {
     return SharedMemoryHandle();
   }
-  SharedMemoryHandle handle = SharedMemoryHandle(result);
+  SharedMemoryHandle handle = SharedMemoryHandle(result, shm_.GetGUID());
   handle.SetOwnershipPassesToIPC(true);
   return handle;
 }
 
 void SharedMemory::Close() {
   if (shm_.IsValid()) {
     shm_.Close();
     shm_ = SharedMemoryHandle();
   }
 }
 
 SharedMemoryHandle SharedMemory::handle() const {
   return shm_;
 }
 
 SharedMemoryHandle SharedMemory::TakeHandle() {
   SharedMemoryHandle handle(shm_);
   handle.SetOwnershipPassesToIPC(true);
   shm_ = SharedMemoryHandle();
   memory_ = nullptr;
   mapped_size_ = 0;
   return handle;
 }
 
 }  // namespace base