From fc1e1aeef9e152f5db4b2b9fce7aab16df03d6cd Mon Sep 17 00:00:00 2001 From: Yifan Hong Date: Tue, 7 Jul 2020 13:23:07 -0700 Subject: [PATCH] Try locking after mounting metadata In rescue mode, if /metadata is mounted but /metadata/ota does not exist, immeidately unmount /metadata and fallback to the code path when /metadata is not mounted; that is, old partitions are overwritten. Test: in recovery, select wipe then immediately sideload Bug: 160457903 Change-Id: I412d62b7005c81a7126106edc471622e6a7ef813 Merged-In: I412d62b7005c81a7126106edc471622e6a7ef813 --- fs_mgr/libsnapshot/snapshot.cpp | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp index 55214f545..688b65820 100644 --- a/fs_mgr/libsnapshot/snapshot.cpp +++ b/fs_mgr/libsnapshot/snapshot.cpp @@ -2520,7 +2520,19 @@ std::unique_ptr SnapshotManager::EnsureMetadataMounted() { LOG(INFO) << "EnsureMetadataMounted does nothing in Android mode."; return std::unique_ptr(new AutoUnmountDevice()); } - return AutoUnmountDevice::New(device_->GetMetadataDir()); + auto ret = AutoUnmountDevice::New(device_->GetMetadataDir()); + if (ret == nullptr) return nullptr; + + // In rescue mode, it is possible to erase and format metadata, but /metadata/ota is not + // created to execute snapshot updates. Hence, subsequent calls is likely to fail because + // Lock*() fails. By failing early and returning nullptr here, update_engine_sideload can + // treat this case as if /metadata is not mounted. + if (!LockShared()) { + LOG(WARNING) << "/metadata is mounted, but errors occur when acquiring a shared lock. " + "Subsequent calls to SnapshotManager will fail. Unmounting /metadata now."; + return nullptr; + } + return ret; } bool SnapshotManager::HandleImminentDataWipe(const std::function& callback) {