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/fsimpl/kernfs/inode_impl_util.go |  2 +-
 pkg/sentry/fsimpl/kernfs/kernfs.go          | 16 ++++++++++++----
 pkg/sentry/fsimpl/kernfs/kernfs_test.go     |  4 ++--
 3 files changed, 15 insertions(+), 7 deletions(-)

(limited to 'pkg/sentry/fsimpl/kernfs')

diff --git a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
index d83c17f83..eac578f25 100644
--- a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
+++ b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
@@ -660,7 +660,7 @@ var _ Inode = (*StaticDirectory)(nil)
 func NewStaticDir(ctx context.Context, creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, perm linux.FileMode, children map[string]Inode, fdOpts GenericDirectoryFDOptions) Inode {
 	inode := &StaticDirectory{}
 	inode.Init(ctx, creds, devMajor, devMinor, ino, perm, fdOpts)
-	inode.EnableLeakCheck()
+	inode.InitRefs()
 
 	inode.OrderedChildren.Init(OrderedChildrenOptions{})
 	links := inode.OrderedChildren.Populate(children)
diff --git a/pkg/sentry/fsimpl/kernfs/kernfs.go b/pkg/sentry/fsimpl/kernfs/kernfs.go
index abb477c7d..c14abcff4 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs.go
@@ -222,7 +222,9 @@ func (d *Dentry) IncRef() {
 	// d.refs may be 0 if d.fs.mu is locked, which serializes against
 	// d.cacheLocked().
 	r := atomic.AddInt64(&d.refs, 1)
-	refsvfs2.LogIncRef(d, r)
+	if d.LogRefs() {
+		refsvfs2.LogIncRef(d, r)
+	}
 }
 
 // TryIncRef implements vfs.DentryImpl.TryIncRef.
@@ -233,7 +235,9 @@ func (d *Dentry) TryIncRef() bool {
 			return false
 		}
 		if atomic.CompareAndSwapInt64(&d.refs, r, r+1) {
-			refsvfs2.LogTryIncRef(d, r+1)
+			if d.LogRefs() {
+				refsvfs2.LogTryIncRef(d, r+1)
+			}
 			return true
 		}
 	}
@@ -242,7 +246,9 @@ func (d *Dentry) TryIncRef() bool {
 // DecRef implements vfs.DentryImpl.DecRef.
 func (d *Dentry) DecRef(ctx context.Context) {
 	r := atomic.AddInt64(&d.refs, -1)
-	refsvfs2.LogDecRef(d, r)
+	if d.LogRefs() {
+		refsvfs2.LogDecRef(d, r)
+	}
 	if r == 0 {
 		d.fs.mu.Lock()
 		d.cacheLocked(ctx)
@@ -254,7 +260,9 @@ func (d *Dentry) DecRef(ctx context.Context) {
 
 func (d *Dentry) decRefLocked(ctx context.Context) {
 	r := atomic.AddInt64(&d.refs, -1)
-	refsvfs2.LogDecRef(d, r)
+	if d.LogRefs() {
+		refsvfs2.LogDecRef(d, r)
+	}
 	if r == 0 {
 		d.cacheLocked(ctx)
 	} else if r < 0 {
diff --git a/pkg/sentry/fsimpl/kernfs/kernfs_test.go b/pkg/sentry/fsimpl/kernfs/kernfs_test.go
index 2418eec44..e63588e33 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs_test.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs_test.go
@@ -109,7 +109,7 @@ func (fs *filesystem) newReadonlyDir(ctx context.Context, creds *auth.Credential
 	dir := &readonlyDir{}
 	dir.attrs.Init(ctx, creds, 0 /* devMajor */, 0 /* devMinor */, fs.NextIno(), linux.ModeDirectory|mode)
 	dir.OrderedChildren.Init(kernfs.OrderedChildrenOptions{})
-	dir.EnableLeakCheck()
+	dir.InitRefs()
 	dir.IncLinks(dir.OrderedChildren.Populate(contents))
 	return dir
 }
@@ -147,7 +147,7 @@ func (fs *filesystem) newDir(ctx context.Context, creds *auth.Credentials, mode
 	dir.fs = fs
 	dir.attrs.Init(ctx, creds, 0 /* devMajor */, 0 /* devMinor */, fs.NextIno(), linux.ModeDirectory|mode)
 	dir.OrderedChildren.Init(kernfs.OrderedChildrenOptions{Writable: true})
-	dir.EnableLeakCheck()
+	dir.InitRefs()
 
 	dir.IncLinks(dir.OrderedChildren.Populate(contents))
 	return dir
-- 
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