Remove the open directory fd check.

sandbox/linux/services/credentials.h

 // Copyright (c) 2013 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.
 
 #ifndef SANDBOX_LINUX_SERVICES_CREDENTIALS_H_
 #define SANDBOX_LINUX_SERVICES_CREDENTIALS_H_
 
 #include "build/build_config.h"
 // Link errors are tedious to track, raise a compile-time error instead.
 #if defined(OS_ANDROID)
 #error "Android is not supported."
 #endif  // defined(OS_ANDROID).
 
 #include <string>
 
 #include "base/basictypes.h"
+#include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "sandbox/sandbox_export.h"
 
 namespace sandbox {
 
 // This class should be used to manipulate the current process' credentials.
 // It is currently a stub used to manipulate POSIX.1e capabilities as
 // implemented by the Linux kernel.
 class SANDBOX_EXPORT Credentials {
  public:
   Credentials();
   ~Credentials();
 
   // Drop all capabilities in the effective, inheritable and permitted sets for
   // the current process.
-  bool DropAllCapabilities();
+  bool DropAllCapabilities() WARN_UNUSED_RESULT;
   // Return true iff there is any capability in any of the capabilities sets
   // of the current process.
   bool HasAnyCapability() const;
   // Returns the capabilities of the current process in textual form, as
   // documented in libcap2's cap_to_text(3). This is mostly useful for
   // debugging and tests.
   scoped_ptr<std::string> GetCurrentCapString() const;
 
   // Returns whether the kernel supports CLONE_NEWUSER and whether it would be
   // possible to immediately move to a new user namespace. There is no point
   // in using this method right before calling MoveToNewUserNS(), simply call
   // MoveToNewUserNS() immediately. This method is only useful to test kernel
   // support ahead of time.
   static bool SupportsNewUserNS();
 
   // Move the current process to a new "user namespace" as supported by Linux
   // 3.8+ (CLONE_NEWUSER).
   // The uid map will be set-up so that the perceived uid and gid will not
   // change.
   // If this call succeeds, the current process will be granted a full set of
   // capabilities in the new namespace.
-  bool MoveToNewUserNS();
+  bool MoveToNewUserNS() WARN_UNUSED_RESULT;
 
   // Remove the ability of the process to access the file system. File
   // descriptors which are already open prior to calling this API remain
   // available.
   // The implementation currently uses chroot(2) and requires CAP_SYS_CHROOT.
   // CAP_SYS_CHROOT can be acquired by using the MoveToNewUserNS() API.
   // Make sure to call DropAllCapabilities() after this call to prevent
   // escapes.
-  // To be secure, it's very important for this API to not be called while the
-  // process has any directory file descriptor open.
-  bool DropFileSystemAccess();
+  // To be secure, the caller must ensure that any directory file descriptors
+  // are closed. Otherwise it may be possible to escape the chroot.
+  bool DropFileSystemAccess() WARN_UNUSED_RESULT;

[jln (very slow on Chromium), 2015/01/05 23:02:32]

Could you point to ProcUtil::HasOpenDirectory() as a way to do that?

[rickyz (no longer on Chrome), 2015/01/06 08:01:20]

Done.

 
  private:
   DISALLOW_COPY_AND_ASSIGN(Credentials);
 };
 
 }  // namespace sandbox.
 
 #endif  // SANDBOX_LINUX_SERVICES_CREDENTIALS_H_