From 0fb5353e45f166460d5846576c20479072207a06 Mon Sep 17 00:00:00 2001
From: Dean Deng <deandeng@google.com>
Date: Mon, 9 Nov 2020 08:30:29 -0800
Subject: Initialize references with a value of 1.

This lets us avoid treating a value of 0 as one reference. All references
using the refsvfs2 template must call InitRefs() before the reference is
incremented/decremented, or else a panic will occur. Therefore, it should be
pretty easy to identify missing InitRef calls during testing.

Updates #1486.

PiperOrigin-RevId: 341411151
---
 pkg/sentry/vfs/file_description.go |  2 +-
 pkg/sentry/vfs/filesystem.go       |  2 +-
 pkg/sentry/vfs/mount.go            | 13 ++++++++++---
 3 files changed, 12 insertions(+), 5 deletions(-)

(limited to 'pkg/sentry/vfs')

diff --git a/pkg/sentry/vfs/file_description.go b/pkg/sentry/vfs/file_description.go
index 546e445aa..936f9fc71 100644
--- a/pkg/sentry/vfs/file_description.go
+++ b/pkg/sentry/vfs/file_description.go
@@ -133,7 +133,7 @@ func (fd *FileDescription) Init(impl FileDescriptionImpl, flags uint32, mnt *Mou
 		}
 	}
 
-	fd.EnableLeakCheck()
+	fd.InitRefs()
 
 	// Remove "file creation flags" to mirror the behavior from file.f_flags in
 	// fs/open.c:do_dentry_open.
diff --git a/pkg/sentry/vfs/filesystem.go b/pkg/sentry/vfs/filesystem.go
index c93d94634..2c4b81e78 100644
--- a/pkg/sentry/vfs/filesystem.go
+++ b/pkg/sentry/vfs/filesystem.go
@@ -48,7 +48,7 @@ type Filesystem struct {
 
 // Init must be called before first use of fs.
 func (fs *Filesystem) Init(vfsObj *VirtualFilesystem, fsType FilesystemType, impl FilesystemImpl) {
-	fs.EnableLeakCheck()
+	fs.InitRefs()
 	fs.vfs = vfsObj
 	fs.fsType = fsType
 	fs.impl = impl
diff --git a/pkg/sentry/vfs/mount.go b/pkg/sentry/vfs/mount.go
index 3ea981ad4..d865fd603 100644
--- a/pkg/sentry/vfs/mount.go
+++ b/pkg/sentry/vfs/mount.go
@@ -169,7 +169,7 @@ func (vfs *VirtualFilesystem) NewMountNamespace(ctx context.Context, creds *auth
 		Owner:       creds.UserNamespace,
 		mountpoints: make(map[*Dentry]uint32),
 	}
-	mntns.EnableLeakCheck()
+	mntns.InitRefs()
 	mntns.root = newMount(vfs, fs, root, mntns, opts)
 	return mntns, nil
 }
@@ -477,7 +477,9 @@ func (mnt *Mount) tryIncMountedRef() bool {
 			return false
 		}
 		if atomic.CompareAndSwapInt64(&mnt.refs, r, r+1) {
-			refsvfs2.LogTryIncRef(mnt, r+1)
+			if mnt.LogRefs() {
+				refsvfs2.LogTryIncRef(mnt, r+1)
+			}
 			return true
 		}
 	}
@@ -488,12 +490,17 @@ func (mnt *Mount) IncRef() {
 	// In general, negative values for mnt.refs are valid because the MSB is
 	// the eager-unmount bit.
 	r := atomic.AddInt64(&mnt.refs, 1)
-	refsvfs2.LogIncRef(mnt, r)
+	if mnt.LogRefs() {
+		refsvfs2.LogIncRef(mnt, r)
+	}
 }
 
 // DecRef decrements mnt's reference count.
 func (mnt *Mount) DecRef(ctx context.Context) {
 	r := atomic.AddInt64(&mnt.refs, -1)
+	if mnt.LogRefs() {
+		refsvfs2.LogDecRef(mnt, r)
+	}
 	if r&^math.MinInt64 == 0 { // mask out MSB
 		refsvfs2.Unregister(mnt)
 		mnt.destroy(ctx)
-- 
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