From 97d2c9a94e802bcb450e50816a913dfc18afc0e3 Mon Sep 17 00:00:00 2001
From: Fabricio Voznika <fvoznika@google.com>
Date: Mon, 25 Nov 2019 11:41:39 -0800
Subject: [PATCH] Use mount hints to determine FileAccessType

PiperOrigin-RevId: 282401165
---
 runsc/boot/fs.go      | 18 ++++++++++++--
 runsc/boot/fs_test.go | 58 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 74 insertions(+), 2 deletions(-)

diff --git a/runsc/boot/fs.go b/runsc/boot/fs.go
index 76036c147..bc9ffaf81 100644
--- a/runsc/boot/fs.go
+++ b/runsc/boot/fs.go
@@ -465,6 +465,13 @@ func (m *mountHint) checkCompatible(mount specs.Mount) error {
 	return nil
 }
 
+func (m *mountHint) fileAccessType() FileAccessType {
+	if m.share == container {
+		return FileAccessExclusive
+	}
+	return FileAccessShared
+}
+
 func filterUnsupportedOptions(mount specs.Mount) []string {
 	rv := make([]string, 0, len(mount.Options))
 	for _, o := range mount.Options {
@@ -764,8 +771,7 @@ func (c *containerMounter) getMountNameAndOptions(conf *Config, m specs.Mount) (
 	case bind:
 		fd := c.fds.remove()
 		fsName = "9p"
-		// Non-root bind mounts are always shared.
-		opts = p9MountOptions(fd, FileAccessShared)
+		opts = p9MountOptions(fd, c.getMountAccessType(m))
 		// If configured, add overlay to all writable mounts.
 		useOverlay = conf.Overlay && !mountFlags(m.Options).ReadOnly
 
@@ -778,6 +784,14 @@ func (c *containerMounter) getMountNameAndOptions(conf *Config, m specs.Mount) (
 	return fsName, opts, useOverlay, nil
 }
 
+func (c *containerMounter) getMountAccessType(mount specs.Mount) FileAccessType {
+	if hint := c.hints.findMount(mount); hint != nil {
+		return hint.fileAccessType()
+	}
+	// Non-root bind mounts are always shared if no hints were provided.
+	return FileAccessShared
+}
+
 // mountSubmount mounts volumes inside the container's root. Because mounts may
 // be readonly, a lower ramfs overlay is added to create the mount point dir.
 // Another overlay is added with tmpfs on top if Config.Overlay is true.
diff --git a/runsc/boot/fs_test.go b/runsc/boot/fs_test.go
index 49ab34b33..0396a4cfb 100644
--- a/runsc/boot/fs_test.go
+++ b/runsc/boot/fs_test.go
@@ -191,3 +191,61 @@ func TestPodMountHintsErrors(t *testing.T) {
 		})
 	}
 }
+
+func TestGetMountAccessType(t *testing.T) {
+	const source = "foo"
+	for _, tst := range []struct {
+		name        string
+		annotations map[string]string
+		want        FileAccessType
+	}{
+		{
+			name: "container=exclusive",
+			annotations: map[string]string{
+				path.Join(MountPrefix, "mount1", "source"): source,
+				path.Join(MountPrefix, "mount1", "type"):   "bind",
+				path.Join(MountPrefix, "mount1", "share"):  "container",
+			},
+			want: FileAccessExclusive,
+		},
+		{
+			name: "pod=shared",
+			annotations: map[string]string{
+				path.Join(MountPrefix, "mount1", "source"): source,
+				path.Join(MountPrefix, "mount1", "type"):   "bind",
+				path.Join(MountPrefix, "mount1", "share"):  "pod",
+			},
+			want: FileAccessShared,
+		},
+		{
+			name: "shared=shared",
+			annotations: map[string]string{
+				path.Join(MountPrefix, "mount1", "source"): source,
+				path.Join(MountPrefix, "mount1", "type"):   "bind",
+				path.Join(MountPrefix, "mount1", "share"):  "shared",
+			},
+			want: FileAccessShared,
+		},
+		{
+			name: "default=shared",
+			annotations: map[string]string{
+				path.Join(MountPrefix, "mount1", "source"): source + "mismatch",
+				path.Join(MountPrefix, "mount1", "type"):   "bind",
+				path.Join(MountPrefix, "mount1", "share"):  "container",
+			},
+			want: FileAccessShared,
+		},
+	} {
+		t.Run(tst.name, func(t *testing.T) {
+			spec := &specs.Spec{Annotations: tst.annotations}
+			podHints, err := newPodMountHints(spec)
+			if err != nil {
+				t.Fatalf("newPodMountHints failed: %v", err)
+			}
+			mounter := containerMounter{hints: podHints}
+			if got := mounter.getMountAccessType(specs.Mount{Source: source}); got != tst.want {
+				t.Errorf("getMountAccessType(), want: %v, got: %v", tst.want, got)
+			}
+		})
+	}
+}