Revert r23911, switch from fork to vfork().

base/process_util_posix.cc

Index: base/process_util_posix.cc
diff --git a/base/process_util_posix.cc b/base/process_util_posix.cc
index d81776f189499cd4ddabe58779be5b87f0838dce..ecb49371e3de32a942706f198c74760ecf8b05ad 100644
--- a/base/process_util_posix.cc
+++ b/base/process_util_posix.cc
@@ -224,40 +224,25 @@ bool LaunchApp(const std::vector<std::string>& argv,
                const environment_vector& environ,
                const file_handle_mapping_vector& fds_to_remap,
                bool wait, ProcessHandle* process_handle) {
-  // We call vfork() for additional performance (avoids touching the page
-  // tables).  This makes things a bit more dangerous since the child and
-  // parent share the same address space and stack.  Try to do most of our
-  // operations before the fork, and hope that everything we do have to do
-  // will be ok...
-  bool use_vfork = (environ.size() == 0);
-
-  InjectiveMultimap fd_shuffle;
-  for (file_handle_mapping_vector::const_iterator
-      it = fds_to_remap.begin(); it != fds_to_remap.end(); ++it) {
-    fd_shuffle.push_back(InjectionArc(it->first, it->second, false));
-  }
-
-  scoped_array<char*> argv_cstr(new char*[argv.size() + 1]);
-  for (size_t i = 0; i < argv.size(); i++)
-    argv_cstr[i] = const_cast<char*>(argv[i].c_str());
-  argv_cstr[argv.size()] = NULL;
-
-  pid_t pid = use_vfork ? vfork() : fork();
+  pid_t pid = fork();
   if (pid < 0)
     return false;
 
   if (pid == 0) {
     // Child process
+    InjectiveMultimap fd_shuffle;
+    for (file_handle_mapping_vector::const_iterator
+        it = fds_to_remap.begin(); it != fds_to_remap.end(); ++it) {
+      fd_shuffle.push_back(InjectionArc(it->first, it->second, false));
+    }
 
-    if (!use_vfork) {
-      for (environment_vector::const_iterator it = environ.begin();
-           it != environ.end(); ++it) {
-        if (it->first) {
-          if (it->second) {
-            setenv(it->first, it->second, 1);
-          } else {
-            unsetenv(it->first);
-          }
+    for (environment_vector::const_iterator it = environ.begin();
+         it != environ.end(); ++it) {
+      if (it->first) {
+        if (it->second) {
+          setenv(it->first, it->second, 1);
+        } else {
+          unsetenv(it->first);
         }
       }
     }
@@ -270,8 +255,17 @@ bool LaunchApp(const std::vector<std::string>& argv,
     if (!ShuffleFileDescriptors(fd_shuffle))
       _exit(127);
 
+    // If we are using the SUID sandbox, it sets a magic environment variable
+    // ("SBX_D"), so we remove that variable from the environment here on the
+    // off chance that it's already set.
+    unsetenv("SBX_D");
+
     CloseSuperfluousFds(fd_shuffle);
 
+    scoped_array<char*> argv_cstr(new char*[argv.size() + 1]);
+    for (size_t i = 0; i < argv.size(); i++)
+      argv_cstr[i] = const_cast<char*>(argv[i].c_str());
+    argv_cstr[argv.size()] = NULL;
     execvp(argv_cstr[0], argv_cstr.get());
     LOG(ERROR) << "LaunchApp: exec failed!, argv_cstr[0] " << argv_cstr[0]
         << ", errno " << errno;