From 91a98487752b21269dd459623a29c0d48bd7bced Mon Sep 17 00:00:00 2001
From: Nikita Ioffe <ioffe@google.com>
Date: Wed, 10 Jun 2020 00:53:59 +0100
Subject: [PATCH] Reboot sequence: Unmount active apexes before unmounting
 /data

Having mounted apexes with loop back devices backing files on /data
partition will prevent clean unmount of it. Unmounting them and tearing
down loop devices should minimize the risk of that.

Note that it won't fix the issue completely, as there are a few (~2-3)
processes that keep restarting even after SIGKILL is sent. Which means
that they can still hold references to apexes on /data partition. But
in practice probability of this is quite low.

Test: adb reboot
Test: put tzdata apex in /data/apex/active && adb reboot
Bug: 158152940
Change-Id: I4624567b3d0f304dba4c6e37b77abd89e57411de
---
 init/reboot.cpp | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/init/reboot.cpp b/init/reboot.cpp
index ec9236140..19e83cc7a 100644
--- a/init/reboot.cpp
+++ b/init/reboot.cpp
@@ -544,6 +544,18 @@ static int StopServicesAndLogViolations(const std::vector<Service*>& services,
     return still_running;
 }
 
+static Result<void> UnmountAllApexes() {
+    const char* args[] = {"/system/bin/apexd", "--unmount-all"};
+    int status;
+    if (logwrap_fork_execvp(arraysize(args), args, &status, false, LOG_KLOG, true, nullptr) != 0) {
+        return ErrnoError() << "Failed to call '/system/bin/apexd --unmount-all'";
+    }
+    if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
+        return {};
+    }
+    return Error() << "'/system/bin/apexd --unmount-all' failed : " << status;
+}
+
 //* Reboot / shutdown the system.
 // cmd ANDROID_RB_* as defined in android_reboot.h
 // reason Reason string like "reboot", "shutdown,userrequested"
@@ -698,6 +710,11 @@ static void DoReboot(unsigned int cmd, const std::string& reason, const std::str
     // 5. drop caches and disable zram backing device, if exist
     KillZramBackingDevice();
 
+    LOG(INFO) << "Ready to unmount apexes. So far shutdown sequence took " << t;
+    // 6. unmount active apexes, otherwise they might prevent clean unmount of /data.
+    if (auto ret = UnmountAllApexes(); !ret.ok()) {
+        LOG(ERROR) << ret.error();
+    }
     UmountStat stat =
             TryUmountAndFsck(cmd, run_fsck, shutdown_timeout - t.duration(), &reboot_semaphore);
     // Follow what linux shutdown is doing: one more sync with little bit delay
@@ -736,18 +753,6 @@ static void LeaveShutdown() {
     StartSendingMessages();
 }
 
-static Result<void> UnmountAllApexes() {
-    const char* args[] = {"/system/bin/apexd", "--unmount-all"};
-    int status;
-    if (logwrap_fork_execvp(arraysize(args), args, &status, false, LOG_KLOG, true, nullptr) != 0) {
-        return ErrnoError() << "Failed to call '/system/bin/apexd --unmount-all'";
-    }
-    if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
-        return {};
-    }
-    return Error() << "'/system/bin/apexd --unmount-all' failed : " << status;
-}
-
 static std::chrono::milliseconds GetMillisProperty(const std::string& name,
                                                    std::chrono::milliseconds default_value) {
     auto value = GetUintProperty(name, static_cast<uint64_t>(default_value.count()));