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// Copyright 2021 The gVisor Authors.
//
// 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.
// safemount_runner is used to test the SafeMount function. Because use of
// unix.Mount requires privilege, tests must launch this process with
// CLONE_NEWNS and CLONE_NEWUSER.
package main
import (
"errors"
"fmt"
"log"
"os"
"path/filepath"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/runsc/specutils"
)
func main() {
// The test temporary directory is the first argument.
tempdir := os.Args[1]
tcs := []struct {
name string
testfunc func() error
}{{
name: "unix.Mount to folder succeeds",
testfunc: func() error {
dir2Path := filepath.Join(tempdir, "subdir2")
if err := unix.Mount(filepath.Join(tempdir, "subdir"), dir2Path, "bind", unix.MS_BIND, ""); err != nil {
return fmt.Errorf("mount: %v", err)
}
return unix.Unmount(dir2Path, unix.MNT_DETACH)
},
}, {
// unix.Mount doesn't care whether the target is a symlink.
name: "unix.Mount to symlink succeeds",
testfunc: func() error {
symlinkPath := filepath.Join(tempdir, "symlink")
if err := unix.Mount(filepath.Join(tempdir, "subdir"), symlinkPath, "bind", unix.MS_BIND, ""); err != nil {
return fmt.Errorf("mount: %v", err)
}
return unix.Unmount(symlinkPath, unix.MNT_DETACH)
},
}, {
name: "SafeMount to folder succeeds",
testfunc: func() error {
dir2Path := filepath.Join(tempdir, "subdir2")
if err := specutils.SafeMount(filepath.Join(tempdir, "subdir"), dir2Path, "bind", unix.MS_BIND, "", "/proc"); err != nil {
return fmt.Errorf("SafeMount: %v", err)
}
return unix.Unmount(dir2Path, unix.MNT_DETACH)
},
}, {
name: "SafeMount to symlink fails",
testfunc: func() error {
err := specutils.SafeMount(filepath.Join(tempdir, "subdir"), filepath.Join(tempdir, "symlink"), "bind", unix.MS_BIND, "", "/proc")
if err == nil {
return fmt.Errorf("SafeMount didn't fail, but should have")
}
var symErr *specutils.ErrSymlinkMount
if !errors.As(err, &symErr) {
return fmt.Errorf("expected SafeMount to fail with ErrSymlinkMount, but got: %v", err)
}
return nil
},
}}
for _, tc := range tcs {
if err := runTest(tempdir, tc.testfunc); err != nil {
log.Fatalf("failed test %q: %v", tc.name, err)
}
}
}
// runTest runs testfunc with the following directory structure:
// tempdir/
// subdir/
// subdir2/
// symlink --> ./subdir2
func runTest(tempdir string, testfunc func() error) error {
// Create tempdir/subdir/.
dirPath := filepath.Join(tempdir, "subdir")
if err := os.Mkdir(dirPath, 0777); err != nil {
return fmt.Errorf("os.Mkdir(%s, 0777)", dirPath)
}
defer os.Remove(dirPath)
// Create tempdir/subdir2/.
dir2Path := filepath.Join(tempdir, "subdir2")
if err := os.Mkdir(dir2Path, 0777); err != nil {
return fmt.Errorf("os.Mkdir(%s, 0777)", dir2Path)
}
defer os.Remove(dir2Path)
// Create tempdir/symlink, which points to ./subdir2.
symlinkPath := filepath.Join(tempdir, "symlink")
if err := os.Symlink("./subdir2", symlinkPath); err != nil {
return fmt.Errorf("failed to create symlink %s: %v", symlinkPath, err)
}
defer os.Remove(symlinkPath)
// Run the actual test.
return testfunc()
}
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