Implement FUSE_WRITE

This commit adds basic write(2) support for FUSE.

1 files changed, 12 insertions, 1 deletions

diff --git a/pkg/sentry/fsimpl/fuse/dev.go b/pkg/sentry/fsimpl/fuse/dev.go
index c53a38021..6022593d6 100644
--- a/pkg/sentry/fsimpl/fuse/dev.go
+++ b/pkg/sentry/fsimpl/fuse/dev.go
@@ -152,7 +152,7 @@ func (fd *DeviceFD) readLocked(ctx context.Context, dst usermem.IOSequence, opts
 	for !fd.queue.Empty() {
 		req = fd.queue.Front()
 
-		if int64(req.hdr.Len) <= dst.NumBytes() {
+		if int64(req.hdr.Len)+int64(len(req.payload)) <= dst.NumBytes() {
 			break
 		}
 
@@ -191,6 +191,17 @@ func (fd *DeviceFD) readLocked(ctx context.Context, dst usermem.IOSequence, opts
 		return 0, syserror.EIO
 	}
 
+	if req.hdr.Opcode == linux.FUSE_WRITE {
+		written, err := dst.DropFirst(n).CopyOut(ctx, req.payload)
+		if err != nil {
+			return 0, err
+		}
+		if written != len(req.payload) {
+			return 0, syserror.EIO
+		}
+		n += int(written)
+	}
+
 	// Fully done with this req, remove it from the queue.
 	fd.queue.Remove(req)
 	if req.hdr.Opcode == linux.FUSE_RELEASE {