linux-kernel - [PATCH 5.3 36/48] io_uring: ensure registered buffer import returns the IO length

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Date:   Tue, 19 Nov 2019 06:19:56 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        李通洲 <carter.li@...tek.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.3 36/48] io_uring: ensure registered buffer import returns the IO length

From: Jens Axboe <axboe@...nel.dk>

commit 5e559561a8d7e6d4adfce6aa8fbf3daa3dec1577 upstream.

A test case was reported where two linked reads with registered buffers
failed the second link always. This is because we set the expected value
of a request in req->result, and if we don't get this result, then we
fail the dependent links. For some reason the registered buffer import
returned -ERROR/0, while the normal import returns -ERROR/length. This
broke linked commands with registered buffers.

Fix this by making io_import_fixed() correctly return the mapped length.

Cc: stable@...r.kernel.org # v5.3
Reported-by: 李通洲 <carter.li@...tek.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/io_uring.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1179,7 +1179,7 @@ static int io_import_fixed(struct io_rin
 		}
 	}

-	return 0;
+	return len;
 }

 static ssize_t io_import_iovec(struct io_ring_ctx *ctx, int rw,