From 5f6b6c16659a25a8379751692c2ffb6c333bd760 Mon Sep 17 00:00:00 2001
From: Andreas Kling <awesomekling@gmail.com>
Date: Sat, 17 Aug 2019 14:24:50 +0200
Subject: [PATCH] Kernel: Do the umount() by the guest's root inode identifier

It was previously possible to unmount a filesystem mounted on /mnt by
doing e.g "umount /mnt/some/path".
---
 Kernel/FileSystem/VirtualFileSystem.cpp | 21 +++++++++++----------
 Kernel/FileSystem/VirtualFileSystem.h   |  2 +-
 Kernel/Process.cpp                      |  7 ++-----
 3 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/Kernel/FileSystem/VirtualFileSystem.cpp b/Kernel/FileSystem/VirtualFileSystem.cpp
index 4053b68c18..3b2b9c5274 100644
--- a/Kernel/FileSystem/VirtualFileSystem.cpp
+++ b/Kernel/FileSystem/VirtualFileSystem.cpp
@@ -58,25 +58,26 @@ KResult VFS::mount(NonnullRefPtr<FS>&& file_system, StringView path)
     return mount(move(file_system), result.value());
 }
 
-KResult VFS::unmount(NonnullRefPtr<FS>&& file_system)
+KResult VFS::unmount(InodeIdentifier guest_inode_id)
 {
     LOCKER(m_lock);
-    dbg() << "VFS: unmount called with fsid " << file_system.ptr()->fsid();
+    dbg() << "VFS: unmount called with inode " << guest_inode_id;
 
-    for (auto i = 0; i < m_mounts.size(); i++) {
-        auto mount = m_mounts.at(i);
-        if (mount.guest_fs().fsid() == file_system.ptr()->fsid()) {
-            if (mount.guest_fs().prepare_to_unmount() != KSuccess) {
-                dbg() << "VFS: Failed to unmount! Device busy";
-                return KResult(-EBUSY);
+    for (int i = 0; i < m_mounts.size(); ++i) {
+        auto& mount = m_mounts.at(i);
+        if (mount.guest() == guest_inode_id) {
+            auto result = mount.guest_fs().prepare_to_unmount();
+            if (result.is_error()) {
+                dbg() << "VFS: Failed to unmount!";
+                return result;
             }
-            dbg() << "VFS: found fs " << file_system.ptr()->fsid() << " at mount " << i << "! Unmounting...";
+            dbg() << "VFS: found fs " << mount.guest_fs().fsid() << " at mount index " << i << "! Unmounting...";
             m_mounts.remove(i);
             return KSuccess;
         }
     }
 
-    dbg() << "VFS: unmount unable to find fsid in m_mounts!";
+    dbg() << "VFS: Nothing mounted on inode " << guest_inode_id;
     return KResult(-ENODEV);
 }
 
diff --git a/Kernel/FileSystem/VirtualFileSystem.h b/Kernel/FileSystem/VirtualFileSystem.h
index 8887fba92c..dcce762312 100644
--- a/Kernel/FileSystem/VirtualFileSystem.h
+++ b/Kernel/FileSystem/VirtualFileSystem.h
@@ -59,7 +59,7 @@ public:
     bool mount_root(NonnullRefPtr<FS>&&);
     KResult mount(NonnullRefPtr<FS>&&, StringView path);
     KResult mount(NonnullRefPtr<FS>&&, Custody& mount_point);
-    KResult unmount(NonnullRefPtr<FS>&&);
+    KResult unmount(InodeIdentifier guest_inode_id);
 
     KResultOr<NonnullRefPtr<FileDescription>> open(StringView path, int options, mode_t mode, Custody& base);
     KResultOr<NonnullRefPtr<FileDescription>> create(StringView path, int options, mode_t mode, Custody& parent_custody);
diff --git a/Kernel/Process.cpp b/Kernel/Process.cpp
index 84a169a1c9..bf5c4b0670 100644
--- a/Kernel/Process.cpp
+++ b/Kernel/Process.cpp
@@ -2811,11 +2811,8 @@ int Process::sys$umount(const char* mountpoint)
     if (metadata_or_error.is_error())
         return metadata_or_error.error();
 
-    auto fsid = metadata_or_error.value().inode.fsid();
-    auto fs = Ext2FS::from_fsid(fsid);
-    auto ret = VFS::the().unmount(*fs);
-
-    return ret;
+    auto guest_inode_id = metadata_or_error.value().inode;
+    return VFS::the().unmount(guest_inode_id);
 }
 
 ProcessTracer& Process::ensure_tracer()