Add a random name to anonymous shared memory sections

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 "base/logging.h"
+#include "base/rand_util.h"
+#include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 
 namespace {
 
 // Returns the length of the memory section starting at the supplied address.
 size_t GetMemorySectionSize(void* address) {
   MEMORY_BASIC_INFORMATION memory_info;
   if (!::VirtualQuery(address, &memory_info, sizeof(memory_info)))
     return 0;
   return memory_info.RegionSize - (static_cast<char*>(address) -
@@ skipping 89 matching lines @@
   if (options.size == 0)
     return false;
 
   // Check maximum accounting for overflow.
   if (options.size >
       static_cast<size_t>(std::numeric_limits<int>::max()) - kSectionMask)
     return false;
 
   size_t rounded_size = (options.size + kSectionMask) & ~kSectionMask;
   name_ = ASCIIToWide(options.name_deprecated == NULL ? "" :
-                          *options.name_deprecated);
+                      *options.name_deprecated);
+  if (name_.empty()) {
+    // Windows ignores DACLs on certain named objects (like shared sections).
+    // So, we generate a random one in case we need the DACL enforced.
+    uint64_t rand_values[4];
+    base::RandBytes(&rand_values, sizeof(rand_values));
+    name_ = base::StringPrintf(L"CrSharedMem_%016x%016x%016x%016x",
+                               rand_values[0], rand_values[1],
+                               rand_values[2], rand_values[3]);
+  }
   mapped_file_ = CreateFileMapping(INVALID_HANDLE_VALUE, NULL,
-      PAGE_READWRITE, 0, static_cast<DWORD>(rounded_size),
-      name_.empty() ? NULL : name_.c_str());
+      PAGE_READWRITE, 0, static_cast<DWORD>(rounded_size), name_.c_str());

[cpu_(ooo_6.6-7.5), 2014/07/23 22:11:43]

lgtm

You are changing the name_ member, won't that confuse the callers, assuming that
there is a method to retrieve the name?

[jschuh, 2014/07/23 22:19:39]

There's no method to retrieve the name, so it shouldn't affect the callers. And
keeping it around seemed handy for debugging purposes.

   if (!mapped_file_)
     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
     // we don't know the size.
     requested_size_ = 0;
@@ skipping 121 matching lines @@
 void SharedMemory::UnlockDeprecated() {
   DCHECK(lock_ != NULL);
   ReleaseMutex(lock_);
 }
 
 SharedMemoryHandle SharedMemory::handle() const {
   return mapped_file_;
 }
 
 }  // namespace base