ChromeOS: Disable ARC when incompatible filesystem is detected.

chrome/browser/chromeos/arc/arc_util.cc

 // Copyright 2017 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 "chrome/browser/chromeos/arc/arc_util.h"
 
+#include <linux/magic.h>
+#include <sys/statfs.h>
+
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"

[xiyuan, 2017/04/04 15:32:21]

nit: not used?

[kinaba, 2017/04/05 02:35:27]

Done.

 #include "base/logging.h"
+#include "base/strings/string_split.h"

[xiyuan, 2017/04/04 15:32:21]

nit: not used?

[kinaba, 2017/04/05 02:35:27]

Done.

+#include "base/sys_info.h"
+#include "base/threading/thread_restrictions.h"
 #include "chrome/browser/chromeos/arc/arc_session_manager.h"
 #include "chrome/browser/chromeos/login/user_flow.h"
 #include "chrome/browser/chromeos/login/users/chrome_user_manager.h"
 #include "chrome/browser/chromeos/profiles/profile_helper.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/pref_names.h"
 #include "components/arc/arc_util.h"
 #include "components/prefs/pref_service.h"
 #include "components/user_manager/user.h"
 #include "components/user_manager/user_manager.h"
@@ skipping 67 matching lines @@
     return false;
   }
 
   // Do not allow for Ephemeral data user. cf) b/26402681
   if (user_manager::UserManager::Get()
           ->IsCurrentUserCryptohomeDataEphemeral()) {
     VLOG(1) << "Users with ephemeral data are not supported in ARC.";
     return false;
   }
 
+  // Do not allow newer version of ARC on old filesystem
+  if (base::SysInfo::IsRunningOnChromeOS()) {

[hidehiko, 2017/04/04 18:35:12]

Could you add a bit more comment about IsRunningOnChromeOS?
Because this is put under chromeos/ directory, so we expect this code compiles
for ChromeOS.
IIUC, the guard is needed for {unit,browser}tests, right?

[kinaba, 2017/04/05 02:35:28]

Done.

+    std::string arc_sdk_version;
+    if (!profile->GetPrefs()->GetBoolean(

[hidehiko, 2017/04/04 18:35:12]

Could you comment the strategy here? We're making sure;
- Underlying file system is compatible with ARC. Or
- SDK version is 23 (meaning M).

Optional: Also, it may be good to briefly mention about the function who and/or
when kArcCompatibileFilesystemChosen value is set?

[kinaba, 2017/04/05 02:35:26]

Done.

+            prefs::kArcCompatibleFilesystemChosen) &&
+        (!base::SysInfo::GetLsbReleaseValue("CHROMEOS_ARC_ANDROID_SDK_VERSION",
+                                            &arc_sdk_version) ||

[Junichi Uekawa, 2017/04/04 23:48:12]

If CHROMEOS_ARC_ANDROID_SDK_VERSION is not there, we assume Android isn't on
this board?
So this path is slightly different.

[kinaba, 2017/04/05 02:35:27]

If Android isn't on the board at all, a check above (IsArcAvailable()) should
have exited this function already.
We don't need to care what to do here in that case. If Android is there but we
failed to read lsb-release,
something bad is happening and thus I'd like to take safer (disable ARC) branch.

+         arc_sdk_version != "23")) {

[Junichi Uekawa, 2017/04/04 23:48:13]

can you name this constant, like: 
constexpr std::string kAndroidMSdkVersion("23");

[kinaba, 2017/04/05 02:35:27]

Done.

+      VLOG(1) << "Users postponed to migrate to dircrypto are not supported.";

[hidehiko, 2017/04/04 18:35:12]

nit/optional: how about output arc_sdk_version here?

[kinaba, 2017/04/05 02:35:28]

Done.

+      return false;
+    }
+  }
+
   return true;
 }
 
 void DisallowArcForTesting() {
   g_disallow_for_testing = true;
 }
 
 bool IsArcPlayStoreEnabledForProfile(const Profile* profile) {
   return IsArcAllowedForProfile(profile) &&
          profile->GetPrefs()->GetBoolean(prefs::kArcEnabled);
@@ skipping 29 matching lines @@
   profile->GetPrefs()->SetBoolean(prefs::kArcEnabled, enabled);
 }
 
 bool AreArcAllOptInPreferencesManagedForProfile(const Profile* profile) {
   return profile->GetPrefs()->IsManagedPreference(
              prefs::kArcBackupRestoreEnabled) &&
          profile->GetPrefs()->IsManagedPreference(
              prefs::kArcLocationServiceEnabled);
 }
 
+bool IsArcCompatibleFilesystem(const base::FilePath& path) {
+  base::ThreadRestrictions::AssertIOAllowed();
+
+  // If it can be verified it is not on ecryptfs, then it is ok.
+  struct statfs statfs_buf;
+  if (statfs(path.value().c_str(), &statfs_buf) < 0)
+    return false;
+  return statfs_buf.f_type != ECRYPTFS_SUPER_MAGIC;
+}
+
 }  // namespace arc