From 8b38d083c42e2706e1ff5a1410fa61d1f5dea3f5 Mon Sep 17 00:00:00 2001
From: Jeff Sharkey <jsharkey@android.com>
Date: Mon, 31 Oct 2016 14:33:49 -0600
Subject: [PATCH] Public volumes belong to a single user.

When a public (vfat) device is inserted, it's strongly associated
with the current foreground user, and no other users should be able
to access it, since otherwise that would be a cross-user data leak.

To use the device under a different user, switch users and then
eject/remount the device.

Test: verified user isolation of USB drive
Bug: 32523490
Change-Id: I590c791996f1fea8d78f625dc942d149f1f41614
---
 .../com/android/externalstorage/ExternalStorageProvider.java   | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/packages/ExternalStorageProvider/src/com/android/externalstorage/ExternalStorageProvider.java b/packages/ExternalStorageProvider/src/com/android/externalstorage/ExternalStorageProvider.java
index 3ef9b8e1b8c4e..10e5dcc916789 100644
--- a/packages/ExternalStorageProvider/src/com/android/externalstorage/ExternalStorageProvider.java
+++ b/packages/ExternalStorageProvider/src/com/android/externalstorage/ExternalStorageProvider.java
@@ -161,7 +161,8 @@ public class ExternalStorageProvider extends DocumentsProvider {
                     final VolumeInfo privateVol = mStorageManager.findPrivateForEmulated(volume);
                     title = mStorageManager.getBestVolumeDescription(privateVol);
                 }
-            } else if (volume.getType() == VolumeInfo.TYPE_PUBLIC) {
+            } else if (volume.getType() == VolumeInfo.TYPE_PUBLIC
+                    && volume.getMountUserId() == userId) {
                 rootId = volume.getFsUuid();
                 title = mStorageManager.getBestVolumeDescription(volume);
             } else {