Support all seek options in gofer specialFileFD.Seek.

Updates #2923.

PiperOrigin-RevId: 317298186

2 files changed, 17 insertions, 18 deletions

diff --git a/pkg/sentry/fsimpl/gofer/regular_file.go b/pkg/sentry/fsimpl/gofer/regular_file.go
index 0d10cf7ac..f7a15a2ed 100644
--- a/pkg/sentry/fsimpl/gofer/regular_file.go
+++ b/pkg/sentry/fsimpl/gofer/regular_file.go
@@ -489,15 +489,24 @@ func (d *dentry) writeback(ctx context.Context, offset, size int64) error {
 func (fd *regularFileFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
 	fd.mu.Lock()
 	defer fd.mu.Unlock()
+	newOffset, err := regularFileSeekLocked(ctx, fd.dentry(), fd.off, offset, whence)
+	if err != nil {
+		return 0, err
+	}
+	fd.off = newOffset
+	return newOffset, nil
+}
+
+// Calculate the new offset for a seek operation on a regular file.
+func regularFileSeekLocked(ctx context.Context, d *dentry, fdOffset, offset int64, whence int32) (int64, error) {
 	switch whence {
 	case linux.SEEK_SET:
 		// Use offset as specified.
 	case linux.SEEK_CUR:
-		offset += fd.off
+		offset += fdOffset
 	case linux.SEEK_END, linux.SEEK_DATA, linux.SEEK_HOLE:
 		// Ensure file size is up to date.
-		d := fd.dentry()
-		if fd.filesystem().opts.interop == InteropModeShared {
+		if !d.cachedMetadataAuthoritative() {
 			if err := d.updateFromGetattr(ctx); err != nil {
 				return 0, err
 			}
@@ -525,7 +534,6 @@ func (fd *regularFileFD) Seek(ctx context.Context, offset int64, whence int32) (
 	if offset < 0 {
 		return 0, syserror.EINVAL
 	}
-	fd.off = offset
 	return offset, nil
 }
 
diff --git a/pkg/sentry/fsimpl/gofer/special_file.go b/pkg/sentry/fsimpl/gofer/special_file.go
index e6e29b329..a92008208 100644
--- a/pkg/sentry/fsimpl/gofer/special_file.go
+++ b/pkg/sentry/fsimpl/gofer/special_file.go
@@ -221,21 +221,12 @@ func (fd *specialFileFD) Seek(ctx context.Context, offset int64, whence int32) (
 	}
 	fd.mu.Lock()
 	defer fd.mu.Unlock()
-	switch whence {
-	case linux.SEEK_SET:
-		// Use offset as given.
-	case linux.SEEK_CUR:
-		offset += fd.off
-	default:
-		// SEEK_END, SEEK_DATA, and SEEK_HOLE aren't supported since it's not
-		// clear that file size is even meaningful for these files.
-		return 0, syserror.EINVAL
-	}
-	if offset < 0 {
-		return 0, syserror.EINVAL
+	newOffset, err := regularFileSeekLocked(ctx, fd.dentry(), fd.off, offset, whence)
+	if err != nil {
+		return 0, err
 	}
-	fd.off = offset
-	return offset, nil
+	fd.off = newOffset
+	return newOffset, nil
 }
 
 // Sync implements vfs.FileDescriptionImpl.Sync.