Add support for getting the real process id from within the suid sandbox. The...

chrome/browser/zygote_host_linux.cc

Index: chrome/browser/zygote_host_linux.cc
===================================================================
--- chrome/browser/zygote_host_linux.cc	(revision 30499)
+++ chrome/browser/zygote_host_linux.cc	(working copy)
@@ -4,13 +4,14 @@
 
 #include "chrome/browser/zygote_host_linux.h"
 
-#include <unistd.h>
-#include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
 
 #include "base/command_line.h"
 #include "base/eintr_wrapper.h"
+#include "base/linux_util.h"
 #include "base/logging.h"
 #include "base/path_service.h"
 #include "base/pickle.h"
@@ -21,6 +22,7 @@
 #include "chrome/browser/renderer_host/render_sandbox_host_linux.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_switches.h"
+#include "chrome/common/process_watcher.h"
 
 #include "sandbox/linux/suid/suid_unsafe_environment_variables.h"
 
@@ -45,7 +47,20 @@
   }
 }
 
-ZygoteHost::ZygoteHost() {
+ZygoteHost::ZygoteHost()
+    : pid_(-1),
+      init_(false) {
+}
+
+ZygoteHost::~ZygoteHost() {
+  if (init_)
+    close(control_fd_);
+}
+
+void ZygoteHost::Init(const std::string& sandbox_cmd) {
+  DCHECK(!init_);
+  init_ = true;
+
   FilePath chrome_path;
   CHECK(PathService::Get(base::FILE_EXE, &chrome_path));
   CommandLine cmd_line(chrome_path);
@@ -82,26 +97,15 @@
                                        switches::kEnableLogging));
   }
 
-  const char* sandbox_binary = NULL;
+  const char* sandbox_binary = sandbox_cmd.c_str();
   struct stat st;
 
-  // In Chromium branded builds, developers can set an environment variable to
-  // use the development sandbox. See
-  // http://code.google.com/p/chromium/wiki/LinuxSUIDSandboxDevelopment
-  if (stat("/proc/self/exe", &st) == 0 &&
-      st.st_uid == getuid()) {
-    sandbox_binary = getenv("CHROME_DEVEL_SANDBOX");
-  }
-
-#if defined(LINUX_SANDBOX_PATH)
-  if (!sandbox_binary)
-    sandbox_binary = LINUX_SANDBOX_PATH;
-#endif
-
-  if (sandbox_binary && stat(sandbox_binary, &st) == 0) {
+  bool using_suid_sandbox = false;
+  if (!sandbox_cmd.empty() && stat(sandbox_binary, &st) == 0) {
     if (access(sandbox_binary, X_OK) == 0 &&
         (st.st_mode & S_ISUID) &&
         (st.st_mode & S_IXOTH)) {
+      using_suid_sandbox = true;
       cmd_line.PrependWrapper(ASCIIToWide(sandbox_binary));
 
       SaveSUIDUnsafeEnvironmentVariables();
@@ -118,22 +122,63 @@
   const int sfd = Singleton<RenderSandboxHostLinux>()->GetRendererSocket();
   fds_to_map.push_back(std::make_pair(sfd, 5));
 
+  int dummy_fd = -1;
+  if (using_suid_sandbox) {
+    dummy_fd = socket(PF_UNIX, SOCK_DGRAM, 0);
+    CHECK(dummy_fd >= 0);
+    fds_to_map.push_back(std::make_pair(dummy_fd, 7));
+  }
+
   base::ProcessHandle process;
   base::LaunchApp(cmd_line.argv(), fds_to_map, false, &process);
   CHECK(process != -1) << "Failed to launch zygote process";
 
-  pid_ = process;
+  if (using_suid_sandbox) {
+    // In the SUID sandbox, the real zygote is forked from the sandbox.
+    // We need to look for it.
+    // But first, wait for the zygote to tell us it's running.
+    // The sending code is in chrome/browser/zygote_main_linux.cc.
+    std::vector<int> fds_vec;
+    const int kExpectedLength = sizeof(kZygoteMagic);
+    char buf[kExpectedLength];
+    const ssize_t len = base::RecvMsg(fds[0], buf, sizeof(buf), &fds_vec);
+    CHECK(len == kExpectedLength) << "Incorrect zygote magic length";
+    CHECK(0 == strcmp(buf, kZygoteMagic)) << "Incorrect zygote magic";
+
+    std::string inode_output;
+    ino_t inode = 0;
+    // Figure out the inode for |dummy_fd|, close |dummy_fd| on our end,
+    // and find the zygote process holding |dummy_fd|.
+    if (base::FileDescriptorGetInode(&inode, dummy_fd)) {
+      close(dummy_fd);
+      std::vector<std::string> get_inode_cmdline;
+      get_inode_cmdline.push_back(sandbox_binary);
+      get_inode_cmdline.push_back(base::kFindInodeSwitch);
+      get_inode_cmdline.push_back(IntToString(inode));
+      CommandLine get_inode_cmd(get_inode_cmdline);
+      if (base::GetAppOutput(get_inode_cmd, &inode_output)) {
+        StringToInt(inode_output, &pid_);
+      }
+    }
+    CHECK(pid_ > 0) << "Did not find zygote process";
+
+    if (process != pid_) {
+      // Reap the sandbox.
+      ProcessWatcher::EnsureProcessGetsReaped(process);
+    }
+  } else {
+    // Not using the SUID sandbox.
+    pid_ = process;
+  }
+
   close(fds[1]);
   control_fd_ = fds[0];
 }
 
-ZygoteHost::~ZygoteHost() {
-  close(control_fd_);
-}
-
 pid_t ZygoteHost::ForkRenderer(
     const std::vector<std::string>& argv,
     const base::GlobalDescriptors::Mapping& mapping) {
+  DCHECK(init_);
   Pickle pickle;
 
   pickle.WriteInt(kCmdFork);
@@ -162,6 +207,7 @@
 }
 
 void ZygoteHost::EnsureProcessTerminated(pid_t process) {
+  DCHECK(init_);
   Pickle pickle;
 
   pickle.WriteInt(kCmdReap);
@@ -172,6 +218,7 @@
 
 bool ZygoteHost::DidProcessCrash(base::ProcessHandle handle,
                                  bool* child_exited) {
+  DCHECK(init_);
   Pickle pickle;
   pickle.WriteInt(kCmdDidProcessCrash);
   pickle.WriteInt(handle);