DPCHECK known conditions when we guess false in CurrentProcessHasOpenDirectories

sandbox/linux/services/credentials.cc

 // 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.
 
 #include "sandbox/linux/services/credentials.h"
 
 #include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
@@ skipping 145 matching lines @@
 Credentials::~Credentials() {
 }
 
 bool Credentials::HasOpenDirectory(int proc_fd) {
   int proc_self_fd = -1;
   if (proc_fd >= 0) {
     proc_self_fd = openat(proc_fd, "self/fd", O_DIRECTORY | O_RDONLY);
   } else {
     proc_self_fd = openat(AT_FDCWD, "/proc/self/fd", O_DIRECTORY | O_RDONLY);
     if (proc_self_fd < 0) {
+      // If this process has been chrooted (eg into /proc/self/fdinfo) then
+      // the new root dir will not have directory listing permissions for us
+      // (hence EACCES).  And if we do have this permission, then /proc won't
+      // exist anyway (hence ENOENT).
+      CHECK(errno == EACCES || errno == ENOENT);

[jln (very slow on Chromium), 2013/11/27 21:26:15]

Do you want to make this a DPCHECK instead?

DCHECK is good enough for this purpose and printing errno will be useful.

[Mostyn Bramley-Moore, 2013/11/28 09:35:32]

Done.

+
       // If not available, guess false.
-      // TODO(mostynb@opera.com): add a CHECK_EQ(ENOENT, errno); Figure out what
-      // other situations are here. http://crbug.com/314985
       return false;
     }
   }
   CHECK_GE(proc_self_fd, 0);
 
   // Ownership of proc_self_fd is transferred here, it must not be closed
   // or modified afterwards except via dir.
   ScopedDIR dir(fdopendir(proc_self_fd));
   CHECK(dir);
 
@@ skipping 78 matching lines @@
 }
 
 bool Credentials::DropFileSystemAccess() {
   // Chrooting to a safe empty dir will only be safe if no directory file
   // descriptor is available to the process.
   DCHECK(!HasOpenDirectory(-1));
   return ChrootToSafeEmptyDir();
 }
 
 }  // namespace sandbox.