container/path: check create and mountinfo helpers

These can quite easily be checked within the framework. The scanner fault injection might require updating at some point if the implementation changes.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/path.go

@@ -111,18 +111,15 @@ func createFile(name string, perm, pperm os.FileMode, content []byte) error {
 	}
 	if content != nil {
 		_, err = f.Write(content)
-		if err != nil {
-			err = wrapErrSelf(err)
 	}
-	}
+	return errors.Join(f.Close(), wrapErrSelf(err))
-	return errors.Join(f.Close(), err)
 }
 
 func ensureFile(name string, perm, pperm os.FileMode) error {
 	fi, err := os.Stat(name)
 	if err != nil {
 		if !os.IsNotExist(err) {
-			return err
+			return wrapErrSelf(err)
 		}
 		return createFile(name, perm, pperm, nil)
 	}

container/path_test.go

@@ -1,6 +1,18 @@
 package container
 
-import "testing"
+import (
+	"errors"
+	"io"
+	"math"
+	"os"
+	"path"
+	"reflect"
+	"syscall"
+	"testing"
+	"unsafe"
+
+	"hakurei.app/container/vfs"
+)
 
 func TestToSysroot(t *testing.T) {
 	testCases := []struct {
@@ -40,3 +52,171 @@ func TestToHost(t *testing.T) {
 
 // InternalToHostOvlEscape exports toHost passed to EscapeOverlayDataSegment.
 func InternalToHostOvlEscape(s string) string { return EscapeOverlayDataSegment(toHost(s)) }
+
+func TestCreateFile(t *testing.T) {
+	t.Run("nonexistent", func(t *testing.T) {
+		if err := createFile(path.Join(Nonexistent, ":3"), 0644, 0755, nil); !os.IsNotExist(err) {
+			t.Errorf("createFile: error = %v", err)
+		}
+		if err := createFile(path.Join(Nonexistent), 0644, 0755, nil); !os.IsNotExist(err) {
+			t.Errorf("createFile: error = %v", err)
+		}
+	})
+
+	t.Run("touch", func(t *testing.T) {
+		tempDir := t.TempDir()
+		pathname := path.Join(tempDir, "empty")
+		if err := createFile(pathname, 0644, 0755, nil); err != nil {
+			t.Fatalf("createFile: error = %v", err)
+		}
+		if d, err := os.ReadFile(pathname); err != nil {
+			t.Fatalf("ReadFile: error = %v", err)
+		} else if len(d) != 0 {
+			t.Fatalf("createFile: %q", string(d))
+		}
+	})
+
+	t.Run("write", func(t *testing.T) {
+		tempDir := t.TempDir()
+		pathname := path.Join(tempDir, "zero")
+		if err := createFile(pathname, 0644, 0755, []byte{0}); err != nil {
+			t.Fatalf("createFile: error = %v", err)
+		}
+		if d, err := os.ReadFile(pathname); err != nil {
+			t.Fatalf("ReadFile: error = %v", err)
+		} else if string(d) != "\x00" {
+			t.Fatalf("createFile: %q, want %q", string(d), "\x00")
+		}
+	})
+}
+
+func TestEnsureFile(t *testing.T) {
+	t.Run("create", func(t *testing.T) {
+		if err := ensureFile(path.Join(t.TempDir(), "ensure"), 0644, 0755); err != nil {
+			t.Errorf("ensureFile: error = %v", err)
+		}
+	})
+
+	t.Run("stat", func(t *testing.T) {
+		t.Run("inaccessible", func(t *testing.T) {
+			tempDir := t.TempDir()
+			pathname := path.Join(tempDir, "inaccessible")
+			if f, err := os.Create(pathname); err != nil {
+				t.Fatalf("Create: error = %v", err)
+			} else {
+				_ = f.Close()
+			}
+
+			if err := os.Chmod(tempDir, 0); err != nil {
+				t.Fatalf("Chmod: error = %v", err)
+			}
+			if err := ensureFile(pathname, 0644, 0755); !errors.Is(err, syscall.EACCES) {
+				t.Errorf("ensureFile: error = %v, want %v", err, syscall.EACCES)
+			}
+			if err := os.Chmod(tempDir, 0755); err != nil {
+				t.Fatalf("Chmod: error = %v", err)
+			}
+		})
+
+		t.Run("directory", func(t *testing.T) {
+			if err := ensureFile(t.TempDir(), 0644, 0755); !errors.Is(err, syscall.EISDIR) {
+				t.Errorf("ensureFile: error = %v, want %v", err, syscall.EISDIR)
+			}
+		})
+
+		t.Run("ensure", func(t *testing.T) {
+			tempDir := t.TempDir()
+			pathname := path.Join(tempDir, "ensure")
+			if f, err := os.Create(pathname); err != nil {
+				t.Fatalf("Create: error = %v", err)
+			} else {
+				_ = f.Close()
+			}
+
+			if err := ensureFile(pathname, 0644, 0755); err != nil {
+				t.Errorf("ensureFile: error = %v", err)
+			}
+		})
+	})
+}
+
+func TestProcPaths(t *testing.T) {
+	t.Run("host", func(t *testing.T) {
+		t.Run("stdout", func(t *testing.T) {
+			want := "/host/proc/self/fd/1"
+			if got := hostProc.stdout(); got != want {
+				t.Errorf("stdout: %q, want %q", got, want)
+			}
+		})
+		t.Run("fd", func(t *testing.T) {
+			want := "/host/proc/self/fd/9223372036854775807"
+			if got := hostProc.fd(math.MaxInt64); got != want {
+				t.Errorf("stdout: %q, want %q", got, want)
+			}
+		})
+	})
+
+	t.Run("mountinfo", func(t *testing.T) {
+		t.Run("nonexistent", func(t *testing.T) {
+			nonexistentProc := newProcPaths(t.TempDir())
+			if err := nonexistentProc.mountinfo(func(*vfs.MountInfoDecoder) error { return syscall.EINVAL }); !os.IsNotExist(err) {
+				t.Errorf("mountinfo: error = %v", err)
+			}
+		})
+
+		t.Run("sample", func(t *testing.T) {
+			tempDir := t.TempDir()
+			if err := os.MkdirAll(path.Join(tempDir, "proc/self"), 0755); err != nil {
+				t.Fatalf("MkdirAll: error = %v", err)
+			}
+
+			t.Run("clean", func(t *testing.T) {
+				if err := os.WriteFile(path.Join(tempDir, "proc/self/mountinfo"), []byte(`15 20 0:3 / /proc rw,relatime - proc /proc rw
+16 20 0:15 / /sys rw,relatime - sysfs /sys rw
+17 20 0:5 / /dev rw,relatime - devtmpfs udev rw,size=1983516k,nr_inodes=495879,mode=755`), 0644); err != nil {
+					t.Fatalf("WriteFile: error = %v", err)
+				}
+
+				var mountInfo *vfs.MountInfo
+				if err := newProcPaths(tempDir).mountinfo(func(d *vfs.MountInfoDecoder) error { return d.Decode(&mountInfo) }); err != nil {
+					t.Fatalf("mountinfo: error = %v", err)
+				}
+
+				wantMountInfo := &vfs.MountInfo{Next: &vfs.MountInfo{Next: &vfs.MountInfo{
+					MountInfoEntry: vfs.MountInfoEntry{ID: 17, Parent: 20, Devno: vfs.DevT{0, 5}, Root: "/", Target: "/dev", VfsOptstr: "rw,relatime", OptFields: []string{}, FsType: "devtmpfs", Source: "udev", FsOptstr: "rw,size=1983516k,nr_inodes=495879,mode=755"}},
+					MountInfoEntry: vfs.MountInfoEntry{ID: 16, Parent: 20, Devno: vfs.DevT{0, 15}, Root: "/", Target: "/sys", VfsOptstr: "rw,relatime", OptFields: []string{}, FsType: "sysfs", Source: "/sys", FsOptstr: "rw"}},
+					MountInfoEntry: vfs.MountInfoEntry{ID: 15, Parent: 20, Devno: vfs.DevT{0, 3}, Root: "/", Target: "/proc", VfsOptstr: "rw,relatime", OptFields: []string{}, FsType: "proc", Source: "/proc", FsOptstr: "rw"},
+				}
+				if !reflect.DeepEqual(mountInfo, wantMountInfo) {
+					t.Errorf("Decode: %#v, want %#v", mountInfo, wantMountInfo)
+				}
+			})
+
+			t.Run("closed", func(t *testing.T) {
+				if err := newProcPaths(tempDir).mountinfo(func(d *vfs.MountInfoDecoder) error {
+					v := reflect.ValueOf(d).Elem().FieldByName("s").Elem().FieldByName("r")
+					v = reflect.NewAt(v.Type(), unsafe.Pointer(v.UnsafeAddr()))
+					if f, ok := v.Elem().Interface().(io.ReadCloser); !ok {
+						t.Fatal("implementation of bufio.Scanner no longer compatible with this fault injection")
+						return syscall.ENOTRECOVERABLE
+					} else {
+						return f.Close()
+					}
+				}); !errors.Is(err, os.ErrClosed) {
+					t.Errorf("mountinfo: error = %v, want %v", err, os.ErrClosed)
+				}
+			})
+
+			t.Run("malformed", func(t *testing.T) {
+				path.Join(tempDir, "proc/self/mountinfo")
+				if err := os.WriteFile(path.Join(tempDir, "proc/self/mountinfo"), []byte{0}, 0644); err != nil {
+					t.Fatalf("WriteFile: error = %v", err)
+				}
+
+				if err := newProcPaths(tempDir).mountinfo(func(d *vfs.MountInfoDecoder) error { return d.Decode(new(*vfs.MountInfo)) }); !errors.Is(err, vfs.ErrMountInfoFields) {
+					t.Fatalf("mountinfo: error = %v, want %v", err, vfs.ErrMountInfoFields)
+				}
+			})
+		})
+	})
+}