fs/splice: don't report a partialResult error if there is no data loss

PiperOrigin-RevId: 288642552

2 files changed, 12 insertions, 0 deletions

diff --git a/pkg/sentry/fs/file.go b/pkg/sentry/fs/file.go
index c0a6e884b..a2f966cb6 100644
--- a/pkg/sentry/fs/file.go
+++ b/pkg/sentry/fs/file.go
@@ -555,6 +555,10 @@ type lockedWriter struct {
 	//
 	// This applies only to Write, not WriteAt.
 	Offset int64
+
+	// Err contains the first error encountered while copying. This is
+	// useful to determine whether Writer or Reader failed during io.Copy.
+	Err error
 }
 
 // Write implements io.Writer.Write.
@@ -590,5 +594,8 @@ func (w *lockedWriter) WriteAt(buf []byte, offset int64) (int, error) {
 			break
 		}
 	}
+	if w.Err == nil {
+		w.Err = err
+	}
 	return written, err
 }
diff --git a/pkg/sentry/fs/splice.go b/pkg/sentry/fs/splice.go
index 311798811..389c330a0 100644
--- a/pkg/sentry/fs/splice.go
+++ b/pkg/sentry/fs/splice.go
@@ -167,6 +167,11 @@ func Splice(ctx context.Context, dst *File, src *File, opts SpliceOpts) (int64,
 		if !srcPipe && !opts.SrcOffset {
 			atomic.StoreInt64(&src.offset, src.offset+n)
 		}
+
+		// Don't report any errors if we have some progress without data loss.
+		if w.Err == nil {
+			err = nil
+		}
 	}
 
 	// Drop locks.