From beb4cb8e436b348efcf4e5f57f0a855991a57363 Mon Sep 17 00:00:00 2001
From: Mark Salyzyn <salyzyn@google.com>
Date: Tue, 6 Nov 2018 08:27:05 -0800
Subject: [PATCH] adb: overlayfs failed to remount /system

Regression introduced commit bb1efbd1c603181f1d9817aa43dad546a55aec29

By not first checking if overlayfs mount on /system is in /proc/mounts
remount fails to discover the override and take the selected action.

Test: adb-remount-test.sh
Bug: 109821005
Change-Id: I1f0bae22caae1bca84fc1e33b508b54d98f4ed5c
---
 adb/daemon/remount_service.cpp   | 10 +++++++++-
 fs_mgr/tests/adb-remount-test.sh |  5 ++---
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/adb/daemon/remount_service.cpp b/adb/daemon/remount_service.cpp
index 2dcfb5330..b72ed1634 100644
--- a/adb/daemon/remount_service.cpp
+++ b/adb/daemon/remount_service.cpp
@@ -97,8 +97,12 @@ static std::string find_mount(const char* dir, bool is_root) {
     }
 }
 
+bool dev_is_overlayfs(const std::string& dev) {
+    return (dev == "overlay") || (dev == "overlayfs");
+}
+
 bool make_block_device_writable(const std::string& dev) {
-    if ((dev == "overlay") || (dev == "overlayfs")) return true;
+    if (dev_is_overlayfs(dev)) return true;
     int fd = unix_open(dev.c_str(), O_RDONLY | O_CLOEXEC);
     if (fd == -1) {
         return false;
@@ -161,6 +165,10 @@ static bool remount_partition(int fd, const char* dir) {
         return true;
     }
     bool is_root = strcmp(dir, "/") == 0;
+    if (is_root && dev_is_overlayfs(find_mount("/system", false))) {
+        dir = "/system";
+        is_root = false;
+    }
     std::string dev = find_mount(dir, is_root);
     if (is_root && dev.empty()) {
         // The fstab entry will be /system if the device switched roots during
diff --git a/fs_mgr/tests/adb-remount-test.sh b/fs_mgr/tests/adb-remount-test.sh
index 6b908d3c3..98c0879d2 100755
--- a/fs_mgr/tests/adb-remount-test.sh
+++ b/fs_mgr/tests/adb-remount-test.sh
@@ -274,9 +274,8 @@ H=`echo "${D}" | head -1` &&
   echo "${D}" | grep "^overlay .* /system\$" >/dev/null ||
   die  "overlay takeover after remount"
 !(adb_sh grep "^overlay " /proc/mounts </dev/null | grep " overlay ro,") &&
-  !(adb_sh grep " rw," /proc/mounts </dev/null |
-  skip_administrative_mounts) ||
-    die "remount overlayfs missed a spot"
+  !(adb_sh grep " rw," /proc/mounts </dev/null | skip_administrative_mounts) ||
+  die "remount overlayfs missed a spot (ro)"
 
 adb_su "sed -n '1,/overlay \\/system/p' /proc/mounts" </dev/null |
   skip_administrative_mounts |