gvisor/pkg/sentry/fs/mount_test.go

// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package fs

import (
	"fmt"
	"testing"

	"gvisor.googlesource.com/gvisor/pkg/sentry/context/contexttest"
)

// cacheReallyContains iterates through the dirent cache to determine whether
// it contains the given dirent.
func cacheReallyContains(cache *DirentCache, d *Dirent) bool {
	for i := cache.list.Front(); i != nil; i = i.Next() {
		if i == d {
			return true
		}
	}
	return false
}

// TestMountSourceOnlyCachedOnce tests that a Dirent that is mounted over only ends
// up in a single Dirent Cache. NOTE(b/63848693): Having a dirent in multiple
// caches causes major consistency issues.
func TestMountSourceOnlyCachedOnce(t *testing.T) {
	ctx := contexttest.Context(t)

	rootCache := NewDirentCache(100)
	rootInode := NewMockInode(ctx, NewMockMountSource(rootCache), StableAttr{
		Type: Directory,
	})
	mm, err := NewMountNamespace(ctx, rootInode)
	if err != nil {
		t.Fatalf("NewMountNamespace failed: %v", err)
	}
	rootDirent := mm.Root()
	defer rootDirent.DecRef()

	// Get a child of the root which we will mount over.  Note that the
	// MockInodeOperations causes Walk to always succeed.
	child, err := rootDirent.Walk(ctx, rootDirent, "child")
	if err != nil {
		t.Fatalf("failed to walk to child dirent: %v", err)
	}
	child.maybeExtendReference() // Cache.

	// Ensure that the root cache contains the child.
	if !cacheReallyContains(rootCache, child) {
		t.Errorf("wanted rootCache to contain child dirent, but it did not")
	}

	// Create a new cache and inode, and mount it over child.
	submountCache := NewDirentCache(100)
	submountInode := NewMockInode(ctx, NewMockMountSource(submountCache), StableAttr{
		Type: Directory,
	})
	if err := mm.Mount(ctx, child, submountInode); err != nil {
		t.Fatalf("failed to mount over child: %v", err)
	}

	// Walk to the child again.
	child2, err := rootDirent.Walk(ctx, rootDirent, "child")
	if err != nil {
		t.Fatalf("failed to walk to child dirent: %v", err)
	}

	// Should have a different Dirent than before.
	if child == child2 {
		t.Fatalf("expected %v not equal to %v, but they are the same", child, child2)
	}

	// Neither of the caches should no contain the child.
	if cacheReallyContains(rootCache, child) {
		t.Errorf("wanted rootCache not to contain child dirent, but it did")
	}
	if cacheReallyContains(submountCache, child) {
		t.Errorf("wanted submountCache not to contain child dirent, but it did")
	}
}

// Test that mounts have proper parent/child relationships.
func TestMountSourceParentChildRelationship(t *testing.T) {
	ctx := contexttest.Context(t)

	rootCache := NewDirentCache(100)
	rootInode := NewMockInode(ctx, NewMockMountSource(rootCache), StableAttr{
		Type: Directory,
	})
	mm, err := NewMountNamespace(ctx, rootInode)
	if err != nil {
		t.Fatalf("NewMountNamespace failed: %v", err)
	}
	rootDirent := mm.Root()
	defer rootDirent.DecRef()

	// Add mounts at the following paths:
	paths := []string{
		"/foo",
		"/foo/bar",
		"/foo/bar/baz",
		"/foo/qux",
		"/waldo",
	}

	var maxTraversals uint
	for _, p := range paths {
		maxTraversals = 0
		d, err := mm.FindLink(ctx, rootDirent, nil, p, &maxTraversals)
		if err != nil {
			t.Fatalf("could not find path %q in mount manager: %v", p, err)
		}
		submountInode := NewMockInode(ctx, NewMockMountSource(nil), StableAttr{
			Type: Directory,
		})
		if err := mm.Mount(ctx, d, submountInode); err != nil {
			t.Fatalf("could not mount at %q: %v", p, err)
		}
	}

	// mm root should contain all submounts (and does not include the root
	// mount).
	allMountSources := rootDirent.Inode.MountSource.Submounts()
	if err := mountPathsAre(rootDirent, allMountSources, paths...); err != nil {
		t.Error(err)
	}

	// Each mount should have a unique ID.
	foundIDs := make(map[uint64]struct{})
	for _, m := range allMountSources {
		id := m.ID()
		if _, ok := foundIDs[id]; ok {
			t.Errorf("got multiple mounts with id %d", id)
		}
		foundIDs[id] = struct{}{}
	}

	// Root mount should have no parent.
	rootMountSource := mm.root.Inode.MountSource
	if p := rootMountSource.Parent(); p != nil {
		t.Errorf("root.Parent got %v wanted nil", p)
	}

	// Root mount should have 2 children: foo and waldo.
	rootChildren := rootMountSource.Children()
	if err := mountPathsAre(rootDirent, rootChildren, "/foo", "/waldo"); err != nil {
		t.Error(err)
	}
	// All root mount children should have root as parent.
	for _, c := range rootChildren {
		if p := c.Parent(); p != rootMountSource {
			t.Errorf("root mount child got parent %+v, wanted root mount", p)
		}
	}

	// "foo" mount should have two children: /foo/bar, and /foo/qux.
	maxTraversals = 0
	d, err := mm.FindLink(ctx, rootDirent, nil, "/foo", &maxTraversals)
	if err != nil {
		t.Fatalf("could not find path %q in mount manager: %v", "/foo", err)
	}
	fooMountSource := d.Inode.MountSource
	fooMountSourceChildren := fooMountSource.Children()
	if err := mountPathsAre(rootDirent, fooMountSourceChildren, "/foo/bar", "/foo/qux"); err != nil {
		t.Error(err)
	}
	// Each child should have fooMountSource as parent.
	for _, c := range fooMountSourceChildren {
		if p := c.Parent(); p != fooMountSource {
			t.Errorf("foo mount child got parent %+v, wanted foo mount", p)
		}
	}
	// Submounts of foo are /foo/bar, /foo/qux, and /foo/bar/baz.
	if err := mountPathsAre(rootDirent, fooMountSource.Submounts(), "/foo/bar", "/foo/qux", "/foo/bar/baz"); err != nil {
		t.Error(err)
	}

	// "waldo" mount should have no submounts or children.
	maxTraversals = 0
	waldo, err := mm.FindLink(ctx, rootDirent, nil, "/waldo", &maxTraversals)
	if err != nil {
		t.Fatalf("could not find path %q in mount manager: %v", "/waldo", err)
	}
	waldoMountSource := waldo.Inode.MountSource
	if got := len(waldoMountSource.Children()); got != 0 {
		t.Errorf("waldo got %d children, wanted 0", got)
	}
	if got := len(waldoMountSource.Submounts()); got != 0 {
		t.Errorf("waldo got %d children, wanted 0", got)
	}
}

func mountPathsAre(root *Dirent, got []*MountSource, want ...string) error {
	if len(got) != len(want) {
		return fmt.Errorf("mount paths have different lengths: got %d want %d", len(got), len(want))
	}
	gotPaths := make(map[string]struct{}, len(got))
	for _, g := range got {
		groot := g.Root()
		n, _ := groot.FullName(root)
		groot.DecRef()
		gotPaths[n] = struct{}{}
	}
	for _, w := range want {
		if _, ok := gotPaths[w]; !ok {
			return fmt.Errorf("no mount with path %q found", w)
		}
	}
	return nil
}