From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Samuel Williams <samuel.williams@oriontransfer.co.nz>,
        Jens Axboe <axboe@kernel.dk>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15 044/128] io_uring: zero iocb->ki_pos for stream file types
Date:   Mon, 27 Dec 2021 16:30:19 +0100
Message-Id: <20211227151332.988615420@linuxfoundation.org>
In-Reply-To: <20211227151331.502501367@linuxfoundation.org>
References: <20211227151331.502501367@linuxfoundation.org>
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From: Jens Axboe <axboe@kernel.dk>

[ Upstream commit 7b9762a5e8837b92a027d58d396a9d27f6440c36 ]

io_uring supports using offset == -1 for using the current file position,
and we read that in as part of read/write command setup. For the non-iter
read/write types we pass in NULL for the position pointer, but for the
iter types we should not be passing any anything but 0 for the position
for a stream.

Clear kiocb->ki_pos if the file is a stream, don't leave it as -1. If we
do, then the request will error with -ESPIPE.

Fixes: ba04291eb66e ("io_uring: allow use of offset == -1 to mean file position")
Link: https://github.com/axboe/liburing/discussions/501
Reported-by: Samuel Williams <samuel.williams@oriontransfer.co.nz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/io_uring.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index e9b06e339c4b0..0006fc7479ca3 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2879,9 +2879,13 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 		req->flags |= REQ_F_ISREG;
 
 	kiocb->ki_pos = READ_ONCE(sqe->off);
-	if (kiocb->ki_pos == -1 && !(file->f_mode & FMODE_STREAM)) {
-		req->flags |= REQ_F_CUR_POS;
-		kiocb->ki_pos = file->f_pos;
+	if (kiocb->ki_pos == -1) {
+		if (!(file->f_mode & FMODE_STREAM)) {
+			req->flags |= REQ_F_CUR_POS;
+			kiocb->ki_pos = file->f_pos;
+		} else {
+			kiocb->ki_pos = 0;
+		}
 	}
 	kiocb->ki_hint = ki_hint_validate(file_write_hint(kiocb->ki_filp));
 	kiocb->ki_flags = iocb_flags(kiocb->ki_filp);
-- 
2.34.1