linux: use /proc/self/exe when exec'ing ourselves

chrome/common/child_process_host.cc

 // Copyright (c) 2009 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 "chrome/common/child_process_host.h"
 
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/file_path.h"
 #include "base/logging.h"
@@ skipping 75 matching lines @@
 
 // static
 FilePath ChildProcessHost::GetChildPath() {
   FilePath child_path;
 
   child_path = CommandLine::ForCurrentProcess()->GetSwitchValuePath(
       switches::kBrowserSubprocessPath);
   if (!child_path.empty())
     return child_path;
 
-#if !defined(OS_MACOSX)
-  // On most platforms, the child executable is the same as the current
-  // executable.
-  PathService::Get(base::FILE_EXE, &child_path);
-#else
+#if defined(OS_LINUX)
+  // Use /proc/self/exe rather than our known binary path so updates
+  // can't swap out the binary from underneath us.
+  child_path = FilePath("/proc/self/exe");
+#elif defined(OS_MACOSX)
   // On the Mac, the child executable lives at a predefined location within
   // the app bundle's versioned directory.
   child_path = chrome::GetVersionedDirectory().
       Append(chrome::kHelperProcessExecutablePath);
-#endif  // OS_MACOSX
+#else
+  // On most platforms, the child executable is the same as the current
+  // executable.
+  PathService::Get(base::FILE_EXE, &child_path);
+#endif
 
   return child_path;
 }
 
 // static
 void ChildProcessHost::SetCrashReporterCommandLine(CommandLine* command_line) {
 #if defined(USE_LINUX_BREAKPAD)
   const bool unattended = (getenv("CHROME_HEADLESS") != NULL);
   if (unattended || GoogleUpdateSettings::GetCollectStatsConsent()) {
     command_line->AppendSwitchWithValue(switches::kEnableCrashReporter,
@@ skipping 153 matching lines @@
 
     return *iterator_;
   } while (true);
 
   return NULL;
 }
 
 bool ChildProcessHost::Iterator::Done() {
   return iterator_ == Singleton<ChildProcessList>::get()->end();
 }