Merge release-20200818.0-56-gdf3c105f4 (automated)

3 files changed, 149 insertions, 0 deletions

diff --git a/pkg/sentry/fsimpl/fuse/fuse_state_autogen.go b/pkg/sentry/fsimpl/fuse/fuse_state_autogen.go
index e4ce04322..f72fe342e 100644
--- a/pkg/sentry/fsimpl/fuse/fuse_state_autogen.go
+++ b/pkg/sentry/fsimpl/fuse/fuse_state_autogen.go
@@ -99,6 +99,29 @@ func (x *futureResponse) StateLoad(m state.Source) {
 	m.Load(3, &x.data)
 }
 
+func (x *inodeRefs) StateTypeName() string {
+	return "pkg/sentry/fsimpl/fuse.inodeRefs"
+}
+
+func (x *inodeRefs) StateFields() []string {
+	return []string{
+		"refCount",
+	}
+}
+
+func (x *inodeRefs) beforeSave() {}
+
+func (x *inodeRefs) StateSave(m state.Sink) {
+	x.beforeSave()
+	m.Save(0, &x.refCount)
+}
+
+func (x *inodeRefs) afterLoad() {}
+
+func (x *inodeRefs) StateLoad(m state.Source) {
+	m.Load(0, &x.refCount)
+}
+
 func (x *requestList) StateTypeName() string {
 	return "pkg/sentry/fsimpl/fuse.requestList"
 }
@@ -155,6 +178,7 @@ func init() {
 	state.Register((*Request)(nil))
 	state.Register((*Response)(nil))
 	state.Register((*futureResponse)(nil))
+	state.Register((*inodeRefs)(nil))
 	state.Register((*requestList)(nil))
 	state.Register((*requestEntry)(nil))
 }
diff --git a/pkg/sentry/fsimpl/fuse/fusefs.go b/pkg/sentry/fsimpl/fuse/fusefs.go
index 44021ee4b..9717c0e15 100644
--- a/pkg/sentry/fsimpl/fuse/fusefs.go
+++ b/pkg/sentry/fsimpl/fuse/fusefs.go
@@ -198,6 +198,7 @@ func (fs *filesystem) Release(ctx context.Context) {
 
 // inode implements kernfs.Inode.
 type inode struct {
+	inodeRefs
 	kernfs.InodeAttrs
 	kernfs.InodeNoDynamicLookup
 	kernfs.InodeNotSymlink
@@ -213,6 +214,7 @@ func (fs *filesystem) newInode(creds *auth.Credentials, mode linux.FileMode) *ke
 	i := &inode{}
 	i.InodeAttrs.Init(creds, linux.UNNAMED_MAJOR, fs.devMinor, fs.NextIno(), linux.ModeDirectory|0755)
 	i.OrderedChildren.Init(kernfs.OrderedChildrenOptions{})
+	i.EnableLeakCheck()
 	i.dentry.Init(i)
 
 	return &i.dentry
@@ -324,3 +326,8 @@ func (i *inode) Stat(ctx context.Context, fs *vfs.Filesystem, opts vfs.StatOptio
 
 	return statFromFUSEAttr(out.Attr, opts.Mask, fusefs.devMinor), nil
 }
+
+// DecRef implements kernfs.Inode.
+func (i *inode) DecRef(context.Context) {
+	i.inodeRefs.DecRef(i.Destroy)
+}
diff --git a/pkg/sentry/fsimpl/fuse/inode_refs.go b/pkg/sentry/fsimpl/fuse/inode_refs.go
new file mode 100644
index 000000000..6b9456e1d
--- /dev/null
+++ b/pkg/sentry/fsimpl/fuse/inode_refs.go
@@ -0,0 +1,118 @@
+package fuse
+
+import (
+	"fmt"
+	"runtime"
+	"sync/atomic"
+
+	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+)
+
+// ownerType is used to customize logging. Note that we use a pointer to T so
+// that we do not copy the entire object when passed as a format parameter.
+var inodeownerType *inode
+
+// Refs implements refs.RefCounter. It keeps a reference count using atomic
+// operations and calls the destructor when the count reaches zero.
+//
+// Note that the number of references is actually refCount + 1 so that a default
+// zero-value Refs object contains one reference.
+//
+// TODO(gvisor.dev/issue/1486): Store stack traces when leak check is enabled in
+// a map with 16-bit hashes, and store the hash in the top 16 bits of refCount.
+// This will allow us to add stack trace information to the leak messages
+// without growing the size of Refs.
+//
+// +stateify savable
+type inodeRefs struct {
+	// refCount is composed of two fields:
+	//
+	//	[32-bit speculative references]:[32-bit real references]
+	//
+	// Speculative references are used for TryIncRef, to avoid a CompareAndSwap
+	// loop. See IncRef, DecRef and TryIncRef for details of how these fields are
+	// used.
+	refCount int64
+}
+
+func (r *inodeRefs) finalize() {
+	var note string
+	switch refs_vfs1.GetLeakMode() {
+	case refs_vfs1.NoLeakChecking:
+		return
+	case refs_vfs1.UninitializedLeakChecking:
+		note = "(Leak checker uninitialized): "
+	}
+	if n := r.ReadRefs(); n != 0 {
+		log.Warningf("%sRefs %p owned by %T garbage collected with ref count of %d (want 0)", note, r, inodeownerType, n)
+	}
+}
+
+// EnableLeakCheck checks for reference leaks when Refs gets garbage collected.
+func (r *inodeRefs) EnableLeakCheck() {
+	if refs_vfs1.GetLeakMode() != refs_vfs1.NoLeakChecking {
+		runtime.SetFinalizer(r, (*inodeRefs).finalize)
+	}
+}
+
+// ReadRefs returns the current number of references. The returned count is
+// inherently racy and is unsafe to use without external synchronization.
+func (r *inodeRefs) ReadRefs() int64 {
+
+	return atomic.LoadInt64(&r.refCount) + 1
+}
+
+// IncRef implements refs.RefCounter.IncRef.
+//
+//go:nosplit
+func (r *inodeRefs) IncRef() {
+	if v := atomic.AddInt64(&r.refCount, 1); v <= 0 {
+		panic(fmt.Sprintf("Incrementing non-positive ref count %p owned by %T", r, inodeownerType))
+	}
+}
+
+// TryIncRef implements refs.RefCounter.TryIncRef.
+//
+// To do this safely without a loop, a speculative reference is first acquired
+// on the object. This allows multiple concurrent TryIncRef calls to distinguish
+// other TryIncRef calls from genuine references held.
+//
+//go:nosplit
+func (r *inodeRefs) TryIncRef() bool {
+	const speculativeRef = 1 << 32
+	v := atomic.AddInt64(&r.refCount, speculativeRef)
+	if int32(v) < 0 {
+
+		atomic.AddInt64(&r.refCount, -speculativeRef)
+		return false
+	}
+
+	atomic.AddInt64(&r.refCount, -speculativeRef+1)
+	return true
+}
+
+// DecRef implements refs.RefCounter.DecRef.
+//
+// Note that speculative references are counted here. Since they were added
+// prior to real references reaching zero, they will successfully convert to
+// real references. In other words, we see speculative references only in the
+// following case:
+//
+//	A: TryIncRef [speculative increase => sees non-negative references]
+//	B: DecRef [real decrease]
+//	A: TryIncRef [transform speculative to real]
+//
+//go:nosplit
+func (r *inodeRefs) DecRef(destroy func()) {
+	switch v := atomic.AddInt64(&r.refCount, -1); {
+	case v < -1:
+		panic(fmt.Sprintf("Decrementing non-positive ref count %p, owned by %T", r, inodeownerType))
+
+	case v == -1:
+
+		if destroy != nil {
+			destroy()
+		}
+	}
+}