From ae2558d900d5eafe2a511f8debe72a8564f5f966 Mon Sep 17 00:00:00 2001
From: Yifan Hong <elsk@google.com>
Date: Tue, 18 Feb 2020 14:19:14 -0800
Subject: [PATCH] libsnapshot: RemoveUpdateState on rollback.

If rollback is detected in ProcessUpdateState, call
RemoveUpdateState and return UpdateState::Cancelled. Now that
update_engine is reponsible for initiating the merge, it can react to
this state and clean up markers appropriately.

Test: libsnapshot_test
Test: apply OTA, manually rollback (by setting the active slot), then
  inspect /metadata/ota as well as /data/misc/update_engine/prefs.

Bug: 147696014

Change-Id: Ibfee11fb50e4f4fb7c6cf02b4921b35e77b8f5a5
Merged-In: Ibfee11fb50e4f4fb7c6cf02b4921b35e77b8f5a5
---
 fs_mgr/libsnapshot/snapshot.cpp | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp
index 152ea9c3e..c51c977db 100644
--- a/fs_mgr/libsnapshot/snapshot.cpp
+++ b/fs_mgr/libsnapshot/snapshot.cpp
@@ -1185,15 +1185,32 @@ bool SnapshotManager::HandleCancelledUpdate(LockedFile* lock,
 
     // If all snapshots were reflashed, then cancel the entire update.
     if (AreAllSnapshotsCancelled(lock)) {
+        LOG(WARNING) << "Detected re-flashing, cancelling unverified update.";
         RemoveAllUpdateState(lock, before_cancel);
         return true;
     }
 
-    // This unverified update might be rolled back, or it might not (b/147347110
-    // comment #77). Take no action, as update_engine is responsible for deciding
-    // whether to cancel.
-    LOG(ERROR) << "Update state is being processed before reboot, taking no action.";
-    return false;
+    // If update has been rolled back, then cancel the entire update.
+    // Client (update_engine) is responsible for doing additional cleanup work on its own states
+    // when ProcessUpdateState() returns UpdateState::Cancelled.
+    auto current_slot = GetCurrentSlot();
+    if (current_slot != Slot::Source) {
+        LOG(INFO) << "Update state is being processed while booting at " << current_slot
+                  << " slot, taking no action.";
+        return false;
+    }
+
+    // current_slot == Source. Attempt to detect rollbacks.
+    if (access(GetRollbackIndicatorPath().c_str(), F_OK) != 0) {
+        // This unverified update is not attempted. Take no action.
+        PLOG(INFO) << "Rollback indicator not detected. "
+                   << "Update state is being processed before reboot, taking no action.";
+        return false;
+    }
+
+    LOG(WARNING) << "Detected rollback, cancelling unverified update.";
+    RemoveAllUpdateState(lock, before_cancel);
+    return true;
 }
 
 std::unique_ptr<LpMetadata> SnapshotManager::ReadCurrentMetadata() {