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From:   Pavel Begunkov <asml.silence@gmail.com>
To:     Jens Axboe <axboe@kernel.dk>, Jann Horn <jannh@google.com>,
        io-uring@vger.kernel.org, linux-kernel@vger.kernel.org
References: <c7dc4d15f9065f41df5ad83e051d05e7c46f004f.1588622410.git.asml.silence@gmail.com>
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Subject: Re: [PATCH for-5.7] io_uring: fix zero len do_splice()
Message-ID: <102cad76-9b98-444f-7ccf-6475245f4031@gmail.com>
Date:   Sat, 9 May 2020 19:07:12 +0300
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On 04/05/2020 23:00, Pavel Begunkov wrote:
> do_splice() doesn't expect len to be 0. Just always return 0 in this
> case as splice(2) do.
> 

If it was missed, may you take a look? I reattached the patch btw killing
reported warnings.

---
From: Pavel Begunkov <asml.silence@gmail.com>
Subject: [PATCH] io_uring: fix zero len do_splice()

do_splice() doesn't expect len to be 0. Do the check in io_splice()
exactly as in sys_splice().

Fixes: 7d67af2c0134 ("io_uring: add splice(2) support")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 65458eda2127..70d8943c337b 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2772,16 +2772,16 @@ static int io_splice(struct io_kiocb *req, bool
force_nonblock)
 	struct file *out = sp->file_out;
 	unsigned int flags = sp->flags & ~SPLICE_F_FD_IN_FIXED;
 	loff_t *poff_in, *poff_out;
-	long ret;
+	long ret = 0;

 	if (force_nonblock)
 		return -EAGAIN;

 	poff_in = (sp->off_in == -1) ? NULL : &sp->off_in;
 	poff_out = (sp->off_out == -1) ? NULL : &sp->off_out;
-	ret = do_splice(in, poff_in, out, poff_out, sp->len, flags);
-	if (force_nonblock && ret == -EAGAIN)
-		return -EAGAIN;
+
+	if (sp->len)
+		ret = do_splice(in, poff_in, out, poff_out, sp->len, flags);

 	io_put_file(req, in, (sp->flags & SPLICE_F_FD_IN_FIXED));
 	req->flags &= ~REQ_F_NEED_CLEANUP;
-- 
2.24.0