[RESTRICT AUTOMERGE][pm] prevent system app downgrades of versions lower than preload

Also remove misleading commandline output.

BUG: 256202273

Test: manual
1. Install preload system app v90, reboot
2. (W/O data, W/ Flag, 90->80 NOK) adb install -d ~/Downloads/PrivApplication_80.apk
Performing Streamed Install
adb: failed to install /usr/local/google/home/schfan/Downloads/PrivApplication_80.apk: Failure [INSTALL_FAILED_VERSION_DOWNGRADE: System app: com.example.privapplication cannot be downgraded to older than its preloaded version on the system image. Update version code 80 is older than current 90]
3. (90->100) Install data app v100
4. (W/ data, W/O Flag, 100->90 NOK) adb install ~/Downloads/PrivApplication_90.apk
Performing Streamed Install
adb: failed to install /usr/local/google/home/schfan/Downloads/PrivApplication_90.apk: Failure [INSTALL_FAILED_VERSION_DOWNGRADE: Downgrade detected: Update version code 90 is older than current 100]
5. (W/ data, W/ Flag, 100->90 downgrade OK) adb install -d ~/Downloads/PrivApplication_90.apk
Performing Streamed Install
Success
6. (90->100) Install v100
6. (W/data, W/ Flag, 100->80 NOK) adb install -d ~/Downloads/PrivApplication_80.apk
Performing Streamed Install
adb: failed to install /usr/local/google/home/schfan/Downloads/PrivApplication_80.apk: Failure [INSTALL_FAILED_VERSION_DOWNGRADE: System app: com.example.privapplication cannot be downgraded to older than its preloaded version on the system image. Update version code 80 is older than current 90]

(cherry picked from commit a4484d7f1be1fa413258fe18644d61f85611f586)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:d7c72817477b7b76ea41a55067057872d5b434bf)
Merged-In: I5a8ee9e29a3a58f6e3fd188e0122355744b8b0ce
Change-Id: I5a8ee9e29a3a58f6e3fd188e0122355744b8b0ce

1 files changed, 22 insertions, 3 deletions

diff --git a/services/core/java/com/android/server/pm/InstallPackageHelper.java b/services/core/java/com/android/server/pm/InstallPackageHelper.java
index 64a9a563e4a2..ae62f4107591 100644
--- a/services/core/java/com/android/server/pm/InstallPackageHelper.java
+++ b/services/core/java/com/android/server/pm/InstallPackageHelper.java
@@ -2429,10 +2429,10 @@ final class InstallPackageHelper {
             // will be null whereas dataOwnerPkg will contain information about the package
             // which was uninstalled while keeping its data.
             AndroidPackage dataOwnerPkg = mPm.mPackages.get(packageName);
+            PackageSetting dataOwnerPs = mPm.mSettings.getPackageLPr(packageName);
             if (dataOwnerPkg  == null) {
-                PackageSetting ps = mPm.mSettings.getPackageLPr(packageName);
-                if (ps != null) {
-                    dataOwnerPkg = ps.getPkg();
+                if (dataOwnerPs != null) {
+                    dataOwnerPkg = dataOwnerPs.getPkg();
                 }
             }
 
@@ -2460,6 +2460,7 @@ final class InstallPackageHelper {
             if (dataOwnerPkg != null && !dataOwnerPkg.isSdkLibrary()) {
                 if (!PackageManagerServiceUtils.isDowngradePermitted(installFlags,
                         dataOwnerPkg.isDebuggable())) {
+                    // Downgrade is not permitted; a lower version of the app will not be allowed
                     try {
                         PackageManagerServiceUtils.checkDowngrade(dataOwnerPkg, pkgLite);
                     } catch (PackageManagerException e) {
@@ -2468,6 +2469,24 @@ final class InstallPackageHelper {
                         return Pair.create(
                                 PackageManager.INSTALL_FAILED_VERSION_DOWNGRADE, errorMsg);
                     }
+                } else if (dataOwnerPs.isSystem()) {
+                    // Downgrade is permitted, but system apps can't be downgraded below
+                    // the version preloaded onto the system image
+                    final PackageSetting disabledPs = mPm.mSettings.getDisabledSystemPkgLPr(
+                            dataOwnerPs);
+                    if (disabledPs != null) {
+                        dataOwnerPkg = disabledPs.getPkg();
+                    }
+                    try {
+                        PackageManagerServiceUtils.checkDowngrade(dataOwnerPkg, pkgLite);
+                    } catch (PackageManagerException e) {
+                        String errorMsg = "System app: " + packageName + " cannot be downgraded to"
+                                + " older than its preloaded version on the system image. "
+                                + e.getMessage();
+                        Slog.w(TAG, errorMsg);
+                        return Pair.create(
+                                PackageManager.INSTALL_FAILED_VERSION_DOWNGRADE, errorMsg);
+                    }
                 }
             }
         }