io_uring: mark ->work uninitialised after cleanup

Remove REQ_F_WORK_INITIALIZED after io_req_clean_work(). That's a cold
path but is safer for those using io_req_clean_work() out of
*dismantle_req()/*io_free(). And for the same reason zero work.fs
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -1141,7 +1141,9 @@ static void io_req_clean_work(struct io_kiocb *req)
 		spin_unlock(&req->work.fs->lock);
 		if (fs)
 			free_fs_struct(fs);
+		req->work.fs = NULL;
 	}
+	req->flags &= ~REQ_F_WORK_INITIALIZED;
 }
 
 static void io_prep_async_work(struct io_kiocb *req)
@@ -4969,7 +4971,6 @@ static int io_poll_add(struct io_kiocb *req)
 
 	/* ->work is in union with hash_node and others */
 	io_req_clean_work(req);
-	req->flags &= ~REQ_F_WORK_INITIALIZED;
 
 	INIT_HLIST_NODE(&req->hash_node);
 	ipt.pt._qproc = io_poll_queue_proc;