wasi: prohibits closing pre-opens

See WebAssembly/wasi-testsuite#50

Signed-off-by: Adrian Cole <adrian@tetrate.io>

imports/wasi_snapshot_preview1/fs.go

@@ -48,6 +48,7 @@ var fdAllocate = stubFunction(
 //
 // The return value is ErrnoSuccess except the following error conditions:
 // - ErrnoBadf: the fd was not open.
+// - ErrnoNotsup: the fs was a pre-open
 //
 // Note: This is similar to `close` in POSIX.
 // See https://github.com/WebAssembly/WASI/blob/main/phases/snapshot/docs.md#fd_close

imports/wasi_snapshot_preview1/fs_test.go

@@ -80,6 +80,14 @@ func Test_fdClose(t *testing.T) {
  require.Equal(t, `
 ==> wasi_snapshot_preview1.fd_close(fd=42)
 <== errno=EBADF
+`, "\n"+log.String())
+ })
+ log.Reset()
+ t.Run("ErrnoNotsup for a preopen", func(t *testing.T) {
+ requireErrno(t, ErrnoNotsup, mod, FdCloseName, uint64(sys.FdPreopen))
+ require.Equal(t, `
+==> wasi_snapshot_preview1.fd_close(fd=3)
+<== errno=ENOTSUP
 `, "\n"+log.String())
  })
 }

internal/sys/fs.go

@@ -259,15 +259,15 @@ func stdinReader(r io.Reader) *FileEntry {
  r = eofReader{}
  }
  s := stdioStat(r, noopStdinStat)
- return &FileEntry{IsPreopen: true, Name: noopStdinStat.Name(), File: &stdioFileReader{r: r, s: s}}
+ return &FileEntry{Name: noopStdinStat.Name(), File: &stdioFileReader{r: r, s: s}}
 }
 
 func stdioWriter(w io.Writer, defaultStat stdioFileInfo) *FileEntry {
  if w == nil {
  w = io.Discard
  }
  s := stdioStat(w, defaultStat)
- return &FileEntry{IsPreopen: true, Name: s.Name(), File: &stdioFileWriter{w: w, s: s}}
+ return &FileEntry{Name: s.Name(), File: &stdioFileWriter{w: w, s: s}}
 }
 
 func stdioStat(f interface{}, defaultStat stdioFileInfo) fs.FileInfo {
@@ -350,6 +350,10 @@ func (c *FSContext) CloseFile(fd uint32) error {
  f, ok := c.openedFiles.Lookup(fd)
  if !ok {
  return syscall.EBADF
+ } else if f.IsPreopen {
+ // WASI is the only user of pre-opens and wasi-testsuite disallows this
+ // See https://github.com/WebAssembly/wasi-testsuite/issues/50
+ return syscall.ENOTSUP
  }
  c.openedFiles.Delete(fd)
  return f.File.Close()

internal/sys/fs_test.go

@@ -20,9 +20,9 @@ import (
 var testCtx = context.WithValue(context.Background(), struct{}{}, "arbitrary")
 
 var (
- noopStdin = &FileEntry{IsPreopen: true, Name: "stdin", File: &stdioFileReader{r: eofReader{}, s: noopStdinStat}}
- noopStdout = &FileEntry{IsPreopen: true, Name: "stdout", File: &stdioFileWriter{w: io.Discard, s: noopStdoutStat}}
- noopStderr = &FileEntry{IsPreopen: true, Name: "stderr", File: &stdioFileWriter{w: io.Discard, s: noopStderrStat}}
+ noopStdin = &FileEntry{Name: "stdin", File: &stdioFileReader{r: eofReader{}, s: noopStdinStat}}
+ noopStdout = &FileEntry{Name: "stdout", File: &stdioFileWriter{w: io.Discard, s: noopStdoutStat}}
+ noopStderr = &FileEntry{Name: "stderr", File: &stdioFileWriter{w: io.Discard, s: noopStderrStat}}
 )
 
 //go:embed testdata
@@ -94,6 +94,40 @@ func TestNewFSContext(t *testing.T) {
  }
 }
 
+func TestFSContext_CloseFile(t *testing.T) {
+ embedFS, err := fs.Sub(testdata, "testdata")
+ require.NoError(t, err)
+ testFS := sysfs.Adapt(embedFS)
+
+ fsc, err := NewFSContext(nil, nil, nil, testFS)
+ require.NoError(t, err)
+ defer fsc.Close(testCtx)
+
+ fdToClose, err := fsc.OpenFile(testFS, "empty.txt", os.O_RDONLY, 0)
+ require.NoError(t, err)
+
+ fdToKeep, err := fsc.OpenFile(testFS, "test.txt", os.O_RDONLY, 0)
+ require.NoError(t, err)
+
+ // Close
+ require.NoError(t, fsc.CloseFile(fdToClose))
+
+ // Verify fdToClose is closed and removed from the opened FDs.
+ _, ok := fsc.LookupFile(fdToClose)
+ require.False(t, ok)
+
+ // Verify fdToKeep is not closed
+ _, ok = fsc.LookupFile(fdToKeep)
+ require.True(t, ok)
+
+ t.Run("EBADF for an invalid FD", func(t *testing.T) {
+ require.Equal(t, syscall.EBADF, fsc.CloseFile(42)) // 42 is an arbitrary invalid FD
+ })
+ t.Run("ENOTSUP for a preopen", func(t *testing.T) {
+ require.Equal(t, syscall.ENOTSUP, fsc.CloseFile(FdPreopen)) // 42 is an arbitrary invalid FD
+ })
+}
+
 func TestUnimplementedFSContext(t *testing.T) {
  testFS, err := NewFSContext(nil, nil, nil, sysfs.UnimplementedFS{})
  require.NoError(t, err)

internal/wasi_snapshot_preview1/errno.go

@@ -281,6 +281,8 @@ func ToErrno(err error) Errno {
  return ErrnoNoent
  case errors.Is(err, syscall.ENOSYS):
  return ErrnoNosys
+ case errors.Is(err, syscall.ENOTSUP):
+ return ErrnoNotsup
  case errors.Is(err, syscall.ENOTDIR):
  return ErrnoNotdir
  case errors.Is(err, syscall.EPERM), errors.Is(err, fs.ErrPermission):