io_uring: fix openat/statx's filename leak

mainline inclusion
from mainline-5.6-rc2
commit 0bdbdd08
category: feature
bugzilla: https://bugzilla.openeuler.org/show_bug.cgi?id=27
CVE: NA
---------------------------

As in the previous patch, make openat*_prep() and statx_prep() handle
double preparation to avoid resource leakage.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Conflicts:
	fs/io_uring.c
[skip io_openat2_prep() for commit cebdb986
 ("io_uring: add support for IORING_OP_OPENAT2") not merged]
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

@@ -2554,6 +2554,8 @@ static int io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return -EINVAL;
 	if (sqe->flags & IOSQE_FIXED_FILE)
 		return -EBADF;
+	if (req->flags & REQ_F_NEED_CLEANUP)
+		return 0;
 
 	req->open.dfd = READ_ONCE(sqe->fd);
 	req->open.mode = READ_ONCE(sqe->len);
@@ -2735,6 +2737,8 @@ static int io_statx_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return -EINVAL;
 	if (sqe->flags & IOSQE_FIXED_FILE)
 		return -EBADF;
+	if (req->flags & REQ_F_NEED_CLEANUP)
+		return 0;
 
 	req->open.dfd = READ_ONCE(sqe->fd);
 	req->open.mask = READ_ONCE(sqe->len);