Enable one PID namespace per process for NaCl processes.

content/zygote/zygote_linux.cc

 // Copyright (c) 2012 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 "content/zygote/zygote_linux.h"
 
 #include <fcntl.h>
 #include <string.h>
 #include <sys/socket.h>
 #include <sys/types.h>
@@ skipping 31 matching lines @@
 // See http://code.google.com/p/chromium/wiki/LinuxZygote
 
 namespace content {
 
 namespace {
 
 // NOP function. See below where this handler is installed.
 void SIGCHLDHandler(int signal) {
 }
 
-// On Linux, when a process is the init process of a PID namespace, it cannot be
-// terminated by signals like SIGTERM or SIGINT, since they are ignored unless
-// we register a handler for them. In the handlers, we exit with this special
-// exit code that GetTerminationStatus understands to mean that we were
-// terminated by an external signal.
-const int kKilledExitCode = 0x80;
-const int kUnexpectedExitCode = 0x81;
-
 int LookUpFd(const base::GlobalDescriptors::Mapping& fd_mapping, uint32_t key) {
   for (size_t index = 0; index < fd_mapping.size(); ++index) {
     if (fd_mapping[index].key == key)
       return fd_mapping[index].fd;
   }
   return -1;
 }
 
 void CreatePipe(base::ScopedFD* read_pipe, base::ScopedFD* write_pipe) {
   int raw_pipe[2];
@@ skipping 239 matching lines @@
       // wait.
       *status = base::GetTerminationStatus(child, exit_code);
     }
   }
   // Successfully got a status for |real_pid|.
   if (*status != base::TERMINATION_STATUS_STILL_RUNNING) {
     // Time to forget about this process.
     process_info_map_.erase(real_pid);
   }
 
-  if (WIFEXITED(*exit_code) && WEXITSTATUS(*exit_code) == kKilledExitCode) {
-    *status = base::TERMINATION_STATUS_PROCESS_WAS_KILLED;
+  if (WIFEXITED(*exit_code)) {
+    const int exit_status = WEXITSTATUS(*exit_code);
+    if (exit_status == sandbox::NamespaceSandbox::SignalExitCode(SIGINT) ||
+        exit_status == sandbox::NamespaceSandbox::SignalExitCode(SIGTERM)) {
+      *status = base::TERMINATION_STATUS_PROCESS_WAS_KILLED;
+    }
   }
 
   return true;
 }
 
 void Zygote::HandleGetTerminationStatus(int fd,
                                         PickleIterator iter) {
   bool known_dead;
   base::ProcessHandle child_requested;
 
@@ skipping 57 matching lines @@
 
     // Helpers should never return in the child process.
     CHECK_NE(pid, 0);
   } else {
     CreatePipe(&read_pipe, &write_pipe);
     if (sandbox_flags_ & kSandboxLinuxPIDNS &&
         sandbox_flags_ & kSandboxLinuxUserNS) {
       pid = sandbox::NamespaceSandbox::ForkInNewPidNamespace(
           /*drop_capabilities_in_child=*/true);
     } else {
-      pid = fork();
+      pid = sandbox::Credentials::ForkAndDropCapabilitiesInChild();
     }
   }
 
   if (pid == 0) {
     // If the process is the init process inside a PID namespace, it must have
     // explicit signal handlers.
     if (getpid() == 1) {
-      for (const int sig : {SIGINT, SIGTERM}) {
+      static const int kTerminationSignals[] = {
+          SIGINT, SIGTERM, SIGHUP, SIGQUIT, SIGABRT, SIGPIPE, SIGUSR1, SIGUSR2};
+      for (const int sig : kTerminationSignals) {
         sandbox::NamespaceSandbox::InstallTerminationSignalHandler(
-            sig, kKilledExitCode);
-      }
-
-      static const int kUnexpectedSignals[] = {
-          SIGHUP, SIGQUIT, SIGABRT, SIGPIPE, SIGUSR1, SIGUSR2,
-      };
-      for (const int sig : kUnexpectedSignals) {
-        sandbox::NamespaceSandbox::InstallTerminationSignalHandler(
-            sig, kUnexpectedExitCode);
+            sig, sandbox::NamespaceSandbox::SignalExitCode(sig));
       }
     }
 
     // In the child process.
     write_pipe.reset();
 
     // Ping the PID oracle socket so the browser can find our PID.
     CHECK(SendZygoteChildPing(pid_oracle.get()));
 
     // Now read back our real PID from the zygote.
@@ skipping 194 matching lines @@
                                     PickleIterator iter) {
   if (HANDLE_EINTR(write(fd, &sandbox_flags_, sizeof(sandbox_flags_))) !=
                    sizeof(sandbox_flags_)) {
     PLOG(ERROR) << "write";
   }
 
   return false;
 }
 
 }  // namespace content