Move a couple of utility functions to a new namespace_utils class.

sandbox/linux/services/credentials_unittest.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 "sandbox/linux/services/credentials.h"
 
 #include <errno.h>
 #include <fcntl.h>
+#include <sched.h>
 #include <stdio.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_file.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/process/launch.h"
 #include "sandbox/linux/tests/unit_tests.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace sandbox {
 
 namespace {
 
 bool WorkingDirectoryIsRoot() {
   char current_dir[PATH_MAX];
   char* cwd = getcwd(current_dir, sizeof(current_dir));
@@ skipping 35 matching lines @@
     fprintf(stdout, "This kernel does not support unprivileged namespaces. "
             "USERNS tests will succeed without running.\n");
     fflush(stdout);
     return;
   }
   CHECK(Credentials::HasAnyCapability());
   CHECK(Credentials::DropAllCapabilities());
   CHECK(!Credentials::HasAnyCapability());
 }
 
-SANDBOX_TEST(Credentials, SupportsUserNS) {
-  CHECK(Credentials::DropAllCapabilities());
-  bool user_ns_supported = Credentials::SupportsNewUserNS();
-  bool moved_to_new_ns = Credentials::MoveToNewUserNS();
-  CHECK_EQ(user_ns_supported, moved_to_new_ns);
-}
-
 SANDBOX_TEST(Credentials, UidIsPreserved) {
   CHECK(Credentials::DropAllCapabilities());
   uid_t old_ruid, old_euid, old_suid;
   gid_t old_rgid, old_egid, old_sgid;
   PCHECK(0 == getresuid(&old_ruid, &old_euid, &old_suid));
   PCHECK(0 == getresgid(&old_rgid, &old_egid, &old_sgid));
   // Probably missing kernel support.
   if (!Credentials::MoveToNewUserNS()) return;
   uid_t new_ruid, new_euid, new_suid;
   PCHECK(0 == getresuid(&new_ruid, &new_euid, &new_suid));
@@ skipping 55 matching lines @@
 // it is not possible to regain capabilities.
 SANDBOX_TEST(Credentials, DISABLE_ON_LSAN(CannotRegainPrivileges)) {
   CHECK(Credentials::DropAllCapabilities());
   // Probably missing kernel support.
   if (!Credentials::MoveToNewUserNS()) return;
   CHECK(Credentials::DropFileSystemAccess());
   CHECK(Credentials::DropAllCapabilities());
 
   // The kernel should now prevent us from regaining capabilities because we
   // are in a chroot.
-  CHECK(!Credentials::SupportsNewUserNS());
+  errno = 0;
+  CHECK_EQ(-1, unshare(CLONE_NEWUSER));

[jln (very slow on Chromium), 2015/01/23 02:48:23]

If we decide to not keep SupportsNewUserNS() under a new name, let's still make
this a separate function!

[rickyz (no longer on Chrome), 2015/01/23 23:59:37]

Ended up keeping the function

+  CHECK_EQ(EPERM, errno);
+
+  errno = 0;
+  CHECK_EQ(-1, base::ForkWithFlags(CLONE_NEWUSER | SIGCHLD, nullptr, nullptr));
+  CHECK_EQ(EPERM, errno);
+
   CHECK(!Credentials::MoveToNewUserNS());
 }
 
 }  // namespace.
 
 }  // namespace sandbox.