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Accept a Window as shown if it's in any transition

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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
This commit is contained in:
Robin Lee
2023-02-23 22:46:41 +01:00
parent 8247263184
commit d98e95c7c8
1 changed files with 7 additions and 4 deletions
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11
services/core/java/com/android/server/wm/WindowState.java
View File

@@ -2018,16 +2018,19 @@ 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() {