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Commit 8ed3e4a8 authored by Robin Lee's avatar Robin Lee Committed by Cherrypicker Worker
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Accept a Window as shown if it's in any transition 

Previously, a malicious or confused app can DoS all other apps with
unshown surfaces by kicking off at least one new transition every
frame.

For example (see linked bug), an app in a busy-loop trying to request
permissions can prevent the launcher from showing Recents.

The significant change here is that when we see that there is a
transition set, we only block on mToken.waitingToShow if mToken
is not already part of another transition. Otherwise, there can
be a new transition generated every frame and the token is constantly
stuck waiting to show.

Test: atest CtsWindowManagerDeviceTestCases
Bug: 269108443
Fix: 271085429
Change-Id: I47ce9fdf5429795cbf083516c19b669bc407d1da
(cherry picked from commit on googleplex-android-review.googlesource.com host: d98e95c7)
Merged-In: I47ce9fdf5429795cbf083516c19b669bc407d1da
parent 9b7e8c61

services/core/java/com/android/server/wm/WindowState.java

+7 −4
Original line number Diff line number Diff line
@@ -2049,16 +2049,19 @@ class WindowState extends WindowContainer<WindowState> implements WindowManagerP 


    /**

     * Like isOnScreen(), but we don't return true if the window is part

     * of a transition that has not yet been started.

     * of a transition but has not yet started animating.

     */

    boolean isReadyForDisplay() {

        if (mToken.waitingToShow && getDisplayContent().mAppTransition.isTransitionSet()) {

        if (!mHasSurface || mDestroying || !isVisibleByPolicy()) {

            return false;

        }

        if (mToken.waitingToShow && getDisplayContent().mAppTransition.isTransitionSet()

                && !isAnimating(TRANSITION | PARENTS, ANIMATION_TYPE_APP_TRANSITION)) {

            return false;

        }

        final boolean parentAndClientVisible = !isParentWindowHidden()

                && mViewVisibility == View.VISIBLE && mToken.isVisible();

        return mHasSurface && isVisibleByPolicy() && !mDestroying

                && (parentAndClientVisible || isAnimating(TRANSITION | PARENTS));

        return parentAndClientVisible || isAnimating(TRANSITION | PARENTS, ANIMATION_TYPE_ALL);

    }



    boolean isFullyTransparent() {