From dc2059fd8b3f5c13984a33ee80e432eebe07c3de Mon Sep 17 00:00:00 2001
From: "Wiktor S. Ovalle Correa" <w.s.ovalle@mudita.com>
Date: Fri, 29 Jan 2021 17:35:19 +0100
Subject: [PATCH] [EGD-5522] Remount fs R/W for backup or update

After setting vFAT to be read only by default backup,
update and factory reset procedures need to remount R/W
first.
---
 .../libiosyscalls/src/syscalls_posix.cpp      | 10 ++++-
 .../service-desktop/ServiceDesktop.cpp        | 37 ++++++++++++++++---
 module-vfs/src/purefs/vfs_subsystem.cpp       |  2 +-
 3 files changed, 41 insertions(+), 8 deletions(-)

diff --git a/board/linux/libiosyscalls/src/syscalls_posix.cpp b/board/linux/libiosyscalls/src/syscalls_posix.cpp
index 893ccbf0b47cbfe74a16c5fc5f51e0f6fa6e6e0e..525b47fbe636ce84d3e13d8115f3421ae5ada968 100644
--- a/board/linux/libiosyscalls/src/syscalls_posix.cpp
+++ b/board/linux/libiosyscalls/src/syscalls_posix.cpp
@@ -625,8 +625,14 @@ extern "C"
         const char *special_file, const char *dir, const char *fstype, unsigned long int rwflag, const void *data)
     {
         if (vfs::redirect_to_image(dir)) {
-            TRACE_SYSCALLN("(%s, %s, %s, %08lx, %p) -> VFS", special_file, dir, fstype, rwflag, data);
-            return vfs::invoke_fs(&fs::mount, special_file, dir, fstype, rwflag, data);
+            TRACE_SYSCALLN("(%s, %s, %s, %08lx, %p) -> VFS",
+                           special_file ? special_file : "(null)",
+                           dir ? dir : "(null)",
+                           fstype ? fstype : "(null)",
+                           rwflag,
+                           data);
+            return vfs::invoke_fs(
+                &fs::mount, special_file ? special_file : "", dir ? dir : "", fstype ? fstype : "", rwflag, data);
         }
         else {
             TRACE_SYSCALLN("(%s, %s, %s, %08lx,%p) -> linux fs", special_file, dir, fstype, rwflag, data);
diff --git a/module-services/service-desktop/ServiceDesktop.cpp b/module-services/service-desktop/ServiceDesktop.cpp
index 2baa6939e793cd2d2597a777475e7c99ec2a26ad..3e14fb3bc421131d2d312a6cb20b1a2e77907eea 100644
--- a/module-services/service-desktop/ServiceDesktop.cpp
+++ b/module-services/service-desktop/ServiceDesktop.cpp
@@ -22,13 +22,32 @@
 #include <cinttypes>
 #include <filesystem>
 
+#include <purefs/filesystem_paths.hpp>
+#include <sys/mount.h>
+#include <sys/statvfs.h>
+
+namespace
+{
+    auto RemountFS(bool readOnly = false, std::string path = std::string(purefs::dir::getRootDiskPath()))
+    {
+        struct statvfs stat;
+        if (auto ret = statvfs(path.c_str(), &stat))
+            return ret;
+        auto flags = stat.f_flag;
+        if (readOnly)
+            flags |= MS_RDONLY;
+        else
+            flags &= ~MS_RDONLY;
+        return mount(NULL, path.c_str(), NULL, flags | MS_REMOUNT, NULL);
+    }
+} // namespace
+
 ServiceDesktop::ServiceDesktop() : sys::Service(service::name::service_desktop, "", sdesktop::service_stack)
 {
     LOG_INFO("[ServiceDesktop] Initializing");
 
     updateOS = std::make_unique<UpdateMuditaOS>(this);
     settings = std::make_unique<settings::Settings>(this);
-
 }
 
 ServiceDesktop::~ServiceDesktop()
@@ -38,7 +57,7 @@ ServiceDesktop::~ServiceDesktop()
 
 sys::ReturnCodes ServiceDesktop::InitHandler()
 {
-    desktopWorker = std::make_unique<WorkerDesktop>(this);
+    desktopWorker  = std::make_unique<WorkerDesktop>(this);
     const bool ret = desktopWorker->init(
         {{sdesktop::RECEIVE_QUEUE_BUFFER_NAME, sizeof(std::string *), sdesktop::cdc_queue_len},
          {sdesktop::SEND_QUEUE_BUFFER_NAME, sizeof(std::string *), sdesktop::cdc_queue_object_size}});
@@ -62,8 +81,9 @@ sys::ReturnCodes ServiceDesktop::InitHandler()
     connect(sdesktop::BackupMessage(), [&](sys::Message *msg) {
         sdesktop::BackupMessage *backupMessage = dynamic_cast<sdesktop::BackupMessage *>(msg);
         if (backupMessage != nullptr) {
-
+            RemountFS();
             BackupRestore::BackupUserFiles(this);
+            RemountFS(true);
         }
         return std::make_shared<sys::ResponseMessage>();
     });
@@ -71,7 +91,7 @@ sys::ReturnCodes ServiceDesktop::InitHandler()
     connect(sdesktop::RestoreMessage(), [&](sys::Message *msg) {
         sdesktop::RestoreMessage *restoreMessage = dynamic_cast<sdesktop::RestoreMessage *>(msg);
         if (restoreMessage != nullptr) {
-
+            RemountFS();
             BackupRestore::RestoreUserFiles(this);
         }
         return std::make_shared<sys::ResponseMessage>();
@@ -81,6 +101,10 @@ sys::ReturnCodes ServiceDesktop::InitHandler()
         auto *factoryMessage = dynamic_cast<sdesktop::FactoryMessage *>(msg);
         if (factoryMessage != nullptr) {
             LOG_DEBUG("ServiceDesktop: FactoryMessage received");
+            RemountFS();
+            // Factory reset calls SystemManager::Reboot(), but
+            // there is no umount() in SystemManager::CloseSystemHandler() -
+            // this might theoretically cause filesystem corruption
             FactoryReset::Run(this);
         }
         return std::make_shared<sys::ResponseMessage>();
@@ -108,8 +132,11 @@ sys::ReturnCodes ServiceDesktop::InitHandler()
                       updateOsMsg->updateStats.uuid);
 
             if (updateOS->setUpdateFile(purefs::dir::getUpdatesOSPath(), updateOsMsg->updateStats.updateFile) ==
-                updateos::UpdateError::NoError)
+                updateos::UpdateError::NoError) {
+                RemountFS();
+                // Same possible issue as with FactoryReset::Run()
                 updateOS->runUpdate();
+            }
         }
         return std::make_shared<sys::ResponseMessage>();
     });
diff --git a/module-vfs/src/purefs/vfs_subsystem.cpp b/module-vfs/src/purefs/vfs_subsystem.cpp
index d8eef58898906e40a7b6c8ed8ec5c5fdbc5828d6..967435fb758644081b234dcef2b5c852e6b9385b 100644
--- a/module-vfs/src/purefs/vfs_subsystem.cpp
+++ b/module-vfs/src/purefs/vfs_subsystem.cpp
@@ -109,7 +109,7 @@ namespace purefs::subsystem
         }
         err = fs_core->register_filesystem("littlefs", std::make_shared<fs::drivers::filesystem_littlefs>());
         if (err) {
-            LOG_FATAL("Unable to register vfat filesystem with error %i", err);
+            LOG_FATAL("Unable to register lfs filesystem with error %i", err);
             return {};
         }