Re: FAILED: patch "[PATCH] io_uring: make offset == -1 consistent with preadv2/pwritev2" failed to apply to 5.8-stable tree

[Jens Axboe <axboe@xxxxxxxxx>]

On 8/31/20 3:59 AM, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
> 
> The patch below does not apply to the 5.8-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.

Here's a backport:


>From 0414a859ee85f9a6b7d692fac115594e19f872ee Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@xxxxxxxxx>
Date: Wed, 26 Aug 2020 10:36:20 -0600
Subject: [PATCH 3/3] io_uring: make offset == -1 consistent with
 preadv2/pwritev2

The man page for io_uring generally claims were consistent with what
preadv2 and pwritev2 accept, but turns out there's a slight discrepancy
in how offset == -1 is handled for pipes/streams. preadv doesn't allow
it, but preadv2 does. This currently causes io_uring to return -EINVAL
if that is attempted, but we should allow that as documented.

This change makes us consistent with preadv2/pwritev2 for just passing
in a NULL ppos for streams if the offset is -1.

Cc: stable@xxxxxxxxxxxxxxx # v5.7+
Reported-by: Benedikt Ames <wisp3rwind@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
 fs/io_uring.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 2b7018456091..4115bfedf15d 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2518,6 +2518,11 @@ static ssize_t io_import_iovec(int rw, struct io_kiocb *req,
 	return import_iovec(rw, buf, sqe_len, UIO_FASTIOV, iovec, iter);
 }
 
+static inline loff_t *io_kiocb_ppos(struct kiocb *kiocb)
+{
+	return kiocb->ki_filp->f_mode & FMODE_STREAM ? NULL : &kiocb->ki_pos;
+}
+
 /*
  * For files that don't have ->read_iter() and ->write_iter(), handle them
  * by looping over ->read() or ->write() manually.
@@ -2553,10 +2558,10 @@ static ssize_t loop_rw_iter(int rw, struct file *file, struct kiocb *kiocb,
 
 		if (rw == READ) {
 			nr = file->f_op->read(file, iovec.iov_base,
-					      iovec.iov_len, &kiocb->ki_pos);
+					      iovec.iov_len, io_kiocb_ppos(kiocb));
 		} else {
 			nr = file->f_op->write(file, iovec.iov_base,
-					       iovec.iov_len, &kiocb->ki_pos);
+					       iovec.iov_len, io_kiocb_ppos(kiocb));
 		}
 
 		if (iov_iter_is_bvec(iter))
@@ -2681,7 +2686,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock)
 		goto copy_iov;
 
 	iov_count = iov_iter_count(&iter);
-	ret = rw_verify_area(READ, req->file, &kiocb->ki_pos, iov_count);
+	ret = rw_verify_area(READ, req->file, io_kiocb_ppos(kiocb), iov_count);
 	if (!ret) {
 		ssize_t ret2;
 
@@ -2780,7 +2785,7 @@ static int io_write(struct io_kiocb *req, bool force_nonblock)
 		goto copy_iov;
 
 	iov_count = iov_iter_count(&iter);
-	ret = rw_verify_area(WRITE, req->file, &kiocb->ki_pos, iov_count);
+	ret = rw_verify_area(WRITE, req->file, io_kiocb_ppos(kiocb), iov_count);
 	if (!ret) {
 		ssize_t ret2;
 
-- 
2.28.0


-- 
Jens Axboe