io_uring: prep req when do IOSQE_ASYNC

mainline inclusion
from mainline-5.6-rc1
commit 1118591a
category: feature
bugzilla: https://bugzilla.openeuler.org/show_bug.cgi?id=27
CVE: NA
---------------------------

Whenever IOSQE_ASYNC is set, requests will be punted to async without
getting into io_issue_req() and without proper preparation done (e.g.
io_req_defer_prep()). Hence they will be left uninitialised.

Prepare them before punting.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: Nyangerkun <yangerkun@huawei.com>
Reviewed-by: Nzhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>

fs/io_uring.c

@@ -4500,11 +4500,15 @@ static void io_queue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	ret = io_req_defer(req, sqe);
 	if (ret) {
 		if (ret != -EIOCBQUEUED) {
+fail_req:
 			io_cqring_add_event(req, ret);
 			req_set_fail_links(req);
 			io_double_put_req(req);
 		}
 	} else if (req->flags & REQ_F_FORCE_ASYNC) {
+		ret = io_req_defer_prep(req, sqe);
+		if (unlikely(ret < 0))
+			goto fail_req;
 		/*
 		 * Never try inline submit of IOSQE_ASYNC is set, go straight
 		 * to async execution.