Revert of Start all children in their own PID namespace.

sandbox/linux/services/namespace_sandbox.cc

Index: sandbox/linux/services/namespace_sandbox.cc
diff --git a/sandbox/linux/services/namespace_sandbox.cc b/sandbox/linux/services/namespace_sandbox.cc
index dfee8b27a7b00d283102605c24aafc2f43f443c4..0f371ebfd3198e77d697e25ece5cfec4e141d164 100644
--- a/sandbox/linux/services/namespace_sandbox.cc
+++ b/sandbox/linux/services/namespace_sandbox.cc
@@ -5,7 +5,6 @@
 #include "sandbox/linux/services/namespace_sandbox.h"
 
 #include <sched.h>
-#include <signal.h>
 #include <stdlib.h>
 #include <sys/types.h>
 #include <unistd.h>
@@ -18,11 +17,9 @@
 #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"
 
 namespace sandbox {
@@ -64,20 +61,6 @@
 const char kSandboxUSERNSEnvironmentVarName[] = "SBX_USER_NS";
 const char kSandboxPIDNSEnvironmentVarName[] = "SBX_PID_NS";
 const char kSandboxNETNSEnvironmentVarName[] = "SBX_NET_NS";
-
-// Linux supports up to 64 signals. This should be updated if that ever changes.
-int g_signal_exit_codes[64];
-
-void TerminationSignalHandler(int sig) {
-  // Return a special exit code so that the process is detected as terminated by
-  // a signal.
-  const size_t sig_idx = static_cast<size_t>(sig);
-  if (sig_idx < arraysize(g_signal_exit_codes)) {
-    _exit(g_signal_exit_codes[sig_idx]);
-  }
-
-  _exit(NamespaceSandbox::kDefaultExitCode);
-}
 
 }  // namespace
 
@@ -128,65 +111,6 @@
 }
 
 // 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);
-  }
-}
-
-// static
-bool NamespaceSandbox::InstallTerminationSignalHandler(
-    int sig,
-    int exit_code) {
-  struct sigaction old_action;
-  PCHECK(sigaction(sig, nullptr, &old_action) == 0);
-
-  if (old_action.sa_flags & SA_SIGINFO &&
-      old_action.sa_sigaction != nullptr) {
-    return false;
-  } else if (old_action.sa_handler != SIG_DFL) {
-    return false;
-  }
-
-  const size_t sig_idx = static_cast<size_t>(sig);
-  CHECK_LT(sig_idx, arraysize(g_signal_exit_codes));
-
-  DCHECK_GE(exit_code, 0);
-  DCHECK_LT(exit_code, 256);
-
-  g_signal_exit_codes[sig_idx] = exit_code;
-
-  struct sigaction action = {};
-  action.sa_handler = &TerminationSignalHandler;
-  PCHECK(sigaction(sig, &action, nullptr) == 0);
-  return true;
-}
-
-// static
 bool NamespaceSandbox::InNewUserNamespace() {
   return getenv(kSandboxUSERNSEnvironmentVarName) != nullptr;
 }