Demo: Build NamespaceSandbox::ForkInNewPidNamespace.

sandbox/linux/services/namespace_sandbox.cc

 // Copyright 2015 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 "sandbox/linux/services/namespace_sandbox.h"
 
 #include <sched.h>
 #include <signal.h>
 #include <stdlib.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/environment.h"
 #include "base/files/scoped_file.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/process/launch.h"
 #include "base/process/process.h"
 #include "sandbox/linux/services/credentials.h"
 #include "sandbox/linux/services/namespace_utils.h"
+#include "sandbox/linux/system_headers/linux_signal.h"
 
 namespace sandbox {
 
 namespace {
 
 const char kSandboxUSERNSEnvironmentVarName[] = "SBX_USER_NS";
 const char kSandboxPIDNSEnvironmentVarName[] = "SBX_PID_NS";
 const char kSandboxNETNSEnvironmentVarName[] = "SBX_NET_NS";
 
 #if !defined(OS_NACL_NONSFI)
@@ skipping 87 matching lines @@
   for (const auto& entry : clone_flag_environ) {
     const int flag = entry.first;
     const char* environ_name = entry.second;
     SetEnvironForNamespaceType(environ, environ_name, clone_flags & flag);
   }
 
   return base::LaunchProcess(argv, launch_options);
 }
 
 // static
-pid_t NamespaceSandbox::ForkInNewPidNamespace(bool drop_capabilities_in_child) {
-  const pid_t pid =
-      base::ForkWithFlags(CLONE_NEWPID | SIGCHLD, nullptr, nullptr);
-  if (pid < 0) {
-    return pid;
-  }
-
-  if (pid == 0) {
-    DCHECK_EQ(1, getpid());
-    if (drop_capabilities_in_child) {
-      // Since we just forked, we are single-threaded, so this should be safe.
-      CHECK(Credentials::DropAllCapabilitiesOnCurrentThread());
-    }
-    return 0;
-  }
-
-  return pid;
-}
-
-// static
 void NamespaceSandbox::InstallDefaultTerminationSignalHandlers() {
   static const int kDefaultTermSignals[] = {
       SIGHUP, SIGINT, SIGABRT, SIGQUIT, SIGPIPE, SIGTERM, SIGUSR1, SIGUSR2,
   };
 
   for (const int sig : kDefaultTermSignals) {
     InstallTerminationSignalHandler(sig, kDefaultExitCode);
   }
 }
 
@@ skipping 20 matching lines @@
   g_signal_exit_codes[sig_idx] = exit_code;
 
   struct sigaction action = {};
   action.sa_handler = &TerminationSignalHandler;
   PCHECK(sigaction(sig, &action, nullptr) == 0);
   return true;
 }
 #endif  // !defined(OS_NACL_NONSFI)
 
 // static
+pid_t NamespaceSandbox::ForkInNewPidNamespace(bool drop_capabilities_in_child) {
+  const pid_t pid =
+      base::ForkWithFlags(CLONE_NEWPID | LINUX_SIGCHLD, nullptr, nullptr);
+  if (pid < 0) {
+    return pid;
+  }
+
+  if (pid == 0) {
+    DCHECK_EQ(1, getpid());
+    if (drop_capabilities_in_child) {
+      // Since we just forked, we are single-threaded, so this should be safe.
+      CHECK(Credentials::DropAllCapabilitiesOnCurrentThread());
+    }
+    return 0;
+  }
+
+  return pid;
+}
+
+// static
 bool NamespaceSandbox::InNewUserNamespace() {
   return getenv(kSandboxUSERNSEnvironmentVarName) != nullptr;
 }
 
 // static
 bool NamespaceSandbox::InNewPidNamespace() {
   return getenv(kSandboxPIDNSEnvironmentVarName) != nullptr;
 }
 
 // static
 bool NamespaceSandbox::InNewNetNamespace() {
   return getenv(kSandboxNETNSEnvironmentVarName) != nullptr;
 }
 
 }  // namespace sandbox