Make Mount.Type optional for bind mounts

According to the OCI spec Mount.Type is an optional field and it
defaults to "bind" when any of "bind" or "rbind" is included in
Mount.Options.

Also fix the shim to remove bind/rbind from options when mount is
converted from bind to tmpfs inside the Sentry.

Fixes #2330
Fixes #3274

PiperOrigin-RevId: 371996891

1 files changed, 30 insertions, 16 deletions

diff --git a/pkg/shim/utils/volumes.go b/pkg/shim/utils/volumes.go
index 52a428179..cdcb88229 100644
--- a/pkg/shim/utils/volumes.go
+++ b/pkg/shim/utils/volumes.go
@@ -91,11 +91,9 @@ func isVolumePath(volume, path string) (bool, error) {
 // UpdateVolumeAnnotations add necessary OCI annotations for gvisor
 // volume optimization.
 func UpdateVolumeAnnotations(bundle string, s *specs.Spec) error {
-	var (
-		uid string
-		err error
-	)
+	var uid string
 	if IsSandbox(s) {
+		var err error
 		uid, err = podUID(s)
 		if err != nil {
 			// Skip if we can't get pod UID, because this doesn't work
@@ -123,21 +121,18 @@ func UpdateVolumeAnnotations(bundle string, s *specs.Spec) error {
 		} else {
 			// This is a container.
 			for i := range s.Mounts {
-				// An error is returned for sandbox if source
-				// annotation is not successfully applied, so
-				// it is guaranteed that the source annotation
-				// for sandbox has already been successfully
-				// applied at this point.
+				// An error is returned for sandbox if source annotation is not
+				// successfully applied, so it is guaranteed that the source annotation
+				// for sandbox has already been successfully applied at this point.
 				//
-				// The volume name is unique inside a pod, so
-				// matching without podUID is fine here.
+				// The volume name is unique inside a pod, so matching without podUID
+				// is fine here.
 				//
-				// TODO: Pass podUID down to shim for containers to do
-				// more accurate matching.
+				// TODO: Pass podUID down to shim for containers to do more accurate
+				// matching.
 				if yes, _ := isVolumePath(volume, s.Mounts[i].Source); yes {
-					// gVisor requires the container mount type to match
-					// sandbox mount type.
-					s.Mounts[i].Type = v
+					// Container mount type must match the sandbox's mount type.
+					changeMountType(&s.Mounts[i], v)
 					updated = true
 				}
 			}
@@ -153,3 +148,22 @@ func UpdateVolumeAnnotations(bundle string, s *specs.Spec) error {
 	}
 	return ioutil.WriteFile(filepath.Join(bundle, "config.json"), b, 0666)
 }
+
+func changeMountType(m *specs.Mount, newType string) {
+	m.Type = newType
+
+	// OCI spec allows bind mounts to be specified in options only. So if new type
+	// is not bind, remove bind/rbind from options.
+	//
+	// "For bind mounts (when options include either bind or rbind), the type is
+	// a dummy, often "none" (not listed in /proc/filesystems)."
+	if newType != "bind" {
+		newOpts := make([]string, 0, len(m.Options))
+		for _, opt := range m.Options {
+			if opt != "rbind" && opt != "bind" {
+				newOpts = append(newOpts, opt)
+			}
+		}
+		m.Options = newOpts
+	}
+}