From 8624560d00c06cf37e1a138d9997479425d4d2b4 Mon Sep 17 00:00:00 2001
From: Cheng Shi <shicheng@xiaomi.corp-partner.google.com>
Date: Thu, 8 Sep 2022 06:43:11 +0000
Subject: [PATCH] Fix the problem that system apps cannot drag

If an app with a uid of Process.SYSTEM_UID calls view.startDragAndDrop, IllegalStateException will be thrown in Session.performDrag, which makes the drag-and-drop feature unavailable in this app.
And we don't need this check either, because validateAndResolveDragMimeTypeExtras and validateDragFlags are indeed called before Binder.clearCallingIdentity.

Bug: 245626682

Change-Id: I1c27287e51a956284dae0f61bfa0cac14dd28a27
---
 services/core/java/com/android/server/wm/Session.java | 11 ++---------
 .../android/server/wm/DragDropControllerTests.java    |  6 ++----
 2 files changed, 4 insertions(+), 13 deletions(-)

diff --git a/services/core/java/com/android/server/wm/Session.java b/services/core/java/com/android/server/wm/Session.java
index 30b50839cd35d..c5f21eb0ef5fa 100644
--- a/services/core/java/com/android/server/wm/Session.java
+++ b/services/core/java/com/android/server/wm/Session.java
@@ -322,7 +322,7 @@ class Session extends IWindowSession.Stub implements IBinder.DeathRecipient {
         final int callingPid = Binder.getCallingPid();
         // Validate and resolve ClipDescription data before clearing the calling identity
         validateAndResolveDragMimeTypeExtras(data, callingUid, callingPid, mPackageName);
-        validateDragFlags(flags, callingUid);
+        validateDragFlags(flags);
         final long ident = Binder.clearCallingIdentity();
         try {
             return mDragDropController.performDrag(mPid, mUid, window, flags, surface, touchSource,
@@ -347,11 +347,7 @@ class Session extends IWindowSession.Stub implements IBinder.DeathRecipient {
      * Validates the given drag flags.
      */
     @VisibleForTesting
-    void validateDragFlags(int flags, int callingUid) {
-        if (callingUid == Process.SYSTEM_UID) {
-            throw new IllegalStateException("Need to validate before calling identify is cleared");
-        }
-
+    void validateDragFlags(int flags) {
         if ((flags & View.DRAG_FLAG_REQUEST_SURFACE_FOR_RETURN_ANIMATION) != 0) {
             if (!mCanStartTasksFromRecents) {
                 throw new SecurityException("Requires START_TASKS_FROM_RECENTS permission");
@@ -365,9 +361,6 @@ class Session extends IWindowSession.Stub implements IBinder.DeathRecipient {
     @VisibleForTesting
     void validateAndResolveDragMimeTypeExtras(ClipData data, int callingUid, int callingPid,
             String callingPackage) {
-        if (callingUid == Process.SYSTEM_UID) {
-            throw new IllegalStateException("Need to validate before calling identify is cleared");
-        }
         final ClipDescription desc = data != null ? data.getDescription() : null;
         if (desc == null) {
             return;
diff --git a/services/tests/wmtests/src/com/android/server/wm/DragDropControllerTests.java b/services/tests/wmtests/src/com/android/server/wm/DragDropControllerTests.java
index 28fc352e2f741..4526d18d63d80 100644
--- a/services/tests/wmtests/src/com/android/server/wm/DragDropControllerTests.java
+++ b/services/tests/wmtests/src/com/android/server/wm/DragDropControllerTests.java
@@ -467,8 +467,7 @@ public class DragDropControllerTests extends WindowTestsBase {
             public void onAnimatorScaleChanged(float scale) {}
         });
         try {
-            session.validateDragFlags(View.DRAG_FLAG_REQUEST_SURFACE_FOR_RETURN_ANIMATION,
-                    TEST_UID);
+            session.validateDragFlags(View.DRAG_FLAG_REQUEST_SURFACE_FOR_RETURN_ANIMATION);
             fail("Expected failure without permission");
         } catch (SecurityException e) {
             // Expected failure
@@ -484,8 +483,7 @@ public class DragDropControllerTests extends WindowTestsBase {
             public void onAnimatorScaleChanged(float scale) {}
         });
         try {
-            session.validateDragFlags(View.DRAG_FLAG_REQUEST_SURFACE_FOR_RETURN_ANIMATION,
-                    TEST_UID);
+            session.validateDragFlags(View.DRAG_FLAG_REQUEST_SURFACE_FOR_RETURN_ANIMATION);
             // Expected pass
         } catch (SecurityException e) {
             fail("Expected no failure with permission");