From 4d60cca9f7061611e6b621202bac8d74b7c1c826 Mon Sep 17 00:00:00 2001
From: Mohammad Samiul Islam <samiul@google.com>
Date: Thu, 15 Oct 2020 01:05:13 +0100
Subject: [PATCH] [DO NOT MERGE] Prevent extra sessions owned by staged install
 from living across restarts

If system server crashes due to external reasons (not due to
exception in pre-reboot verifications), then the staged install will be
retried. But, any extra sessions that have not been cleaned up will
linger on until removed due to old age.

And if the crash keeps on happening every time at the worst possible
time, then we can have 1024 extra sessions created all with copies of
apks in it. It will waste a lot of user's space.

With this CL, we cleanup any leftover extra sessions whenever system
server is restarted.

Bug: 170784748
Test: manual
Test: verified that without this CL if system server crashses after
extra sessions are created but before they are cleaned up, then folders
start to pile up in /data/app folder with copy of the apks inside.

Change-Id: I5c19093853e28c668f882d37691959b1ac2464cc
---
 .../com/android/server/pm/PackageInstallerService.java   | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/services/core/java/com/android/server/pm/PackageInstallerService.java b/services/core/java/com/android/server/pm/PackageInstallerService.java
index 330f995235071..56ef468407c4a 100644
--- a/services/core/java/com/android/server/pm/PackageInstallerService.java
+++ b/services/core/java/com/android/server/pm/PackageInstallerService.java
@@ -393,6 +393,8 @@ public class PackageInstallerService extends IPackageInstaller.Stub implements
                             Slog.w(TAG, "Abandoning old session created at "
                                         + session.createdMillis);
                             valid = false;
+                        } else if (isExtraSessionForStagedInstall(session)) {
+                            valid = false;
                         } else {
                             valid = true;
                         }
@@ -423,6 +425,13 @@ public class PackageInstallerService extends IPackageInstaller.Stub implements
         }
     }
 
+    // Extra sessions are created during staged install on temporary basis. They should not be
+    // allowed to live across system server restart.
+    private boolean isExtraSessionForStagedInstall(PackageInstallerSession session) {
+        return (session.params.installFlags & PackageManager.INSTALL_DRY_RUN) != 0
+                || (session.params.installFlags & PackageManager.INSTALL_DISABLE_VERIFICATION) != 0;
+    }
+
     @GuardedBy("mSessions")
     private void addHistoricalSessionLocked(PackageInstallerSession session) {
         CharArrayWriter writer = new CharArrayWriter();