From 00f8663887cbf9057d93e8848eb9538cf1c0cff4 Mon Sep 17 00:00:00 2001 From: Andrei Vagin Date: Mon, 3 Jun 2019 21:24:56 -0700 Subject: gvisor/fs: return a proper error from FileWriter.Write in case of a short-write The io.Writer contract requires that Write writes all available bytes and does not return short writes. This causes errors with io.Copy, since our own Write interface does not have this same contract. PiperOrigin-RevId: 251368730 --- pkg/sentry/fs/file.go | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) (limited to 'pkg') diff --git a/pkg/sentry/fs/file.go b/pkg/sentry/fs/file.go index 8c1307235..f64954457 100644 --- a/pkg/sentry/fs/file.go +++ b/pkg/sentry/fs/file.go @@ -545,12 +545,28 @@ type lockedWriter struct { // Write implements io.Writer.Write. func (w *lockedWriter) Write(buf []byte) (int, error) { - n, err := w.File.FileOperations.Write(w.Ctx, w.File, usermem.BytesIOSequence(buf), w.File.offset) - return int(n), err + return w.WriteAt(buf, w.File.offset) } // WriteAt implements io.Writer.WriteAt. func (w *lockedWriter) WriteAt(buf []byte, offset int64) (int, error) { - n, err := w.File.FileOperations.Write(w.Ctx, w.File, usermem.BytesIOSequence(buf), offset) - return int(n), err + var ( + written int + err error + ) + // The io.Writer contract requires that Write writes all available + // bytes and does not return short writes. This causes errors with + // io.Copy, since our own Write interface does not have this same + // contract. Enforce that here. + for written < len(buf) { + var n int64 + n, err = w.File.FileOperations.Write(w.Ctx, w.File, usermem.BytesIOSequence(buf[written:]), offset+int64(written)) + if n > 0 { + written += int(n) + } + if err != nil { + break + } + } + return written, err } -- cgit v1.2.3