All of lore.kernel.org
 help / color / mirror / Atom feed
From: Jens Axboe <axboe@kernel.dk>
To: gregkh@linuxfoundation.org, dylany@meta.com
Cc: stable@vger.kernel.org
Subject: Re: FAILED: patch "[PATCH] io_uring: always prep_async for drain requests" failed to apply to 6.1-stable tree
Date: Sun, 29 Jan 2023 12:40:11 -0700	[thread overview]
Message-ID: <1aa4166f-c66b-5eea-e695-66f206482321@kernel.dk> (raw)
In-Reply-To: <1674998787177121@kroah.com>

[-- Attachment #1: Type: text/plain, Size: 333 bytes --]

On 1/29/23 6:26 AM, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 6.1-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@vger.kernel.org>.

This should do it.

-- 
Jens Axboe


[-- Attachment #2: 0001-io_uring-always-prep_async-for-drain-requests.patch --]
[-- Type: text/x-patch, Size: 2549 bytes --]

From 71a58ab8cf1bb4b4c286fbabe266a82bab20fdf2 Mon Sep 17 00:00:00 2001
From: Dylan Yudaken <dylany@meta.com>
Date: Sun, 29 Jan 2023 12:34:51 -0700
Subject: [PATCH] io_uring: always prep_async for drain requests

commit ef5c600adb1d985513d2b612cc90403a148ff287 upstream.

Drain requests all go through io_drain_req, which has a quick exit in case
there is nothing pending (ie the drain is not useful). In that case it can
run the issue the request immediately.

However for safety it queues it through task work.
The problem is that in this case the request is run asynchronously, but
the async work has not been prepared through io_req_prep_async.

This has not been a problem up to now, as the task work always would run
before returning to userspace, and so the user would not have a chance to
race with it.

However - with IORING_SETUP_DEFER_TASKRUN - this is no longer the case and
the work might be defered, giving userspace a chance to change data being
referred to in the request.

Instead _always_ prep_async for drain requests, which is simpler anyway
and removes this issue.

Cc: stable@vger.kernel.org
Fixes: c0e0d6ba25f1 ("io_uring: add IORING_SETUP_DEFER_TASKRUN")
Signed-off-by: Dylan Yudaken <dylany@meta.com>
Link: https://lore.kernel.org/r/20230127105911.2420061-1-dylany@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 io_uring/io_uring.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index cea5de98c423..6fc4aaef5fe2 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1658,17 +1658,12 @@ static __cold void io_drain_req(struct io_kiocb *req)
 	}
 	spin_unlock(&ctx->completion_lock);
 
-	ret = io_req_prep_async(req);
-	if (ret) {
-fail:
-		io_req_complete_failed(req, ret);
-		return;
-	}
 	io_prep_async_link(req);
 	de = kmalloc(sizeof(*de), GFP_KERNEL);
 	if (!de) {
 		ret = -ENOMEM;
-		goto fail;
+		io_req_complete_failed(req, ret);
+		return;
 	}
 
 	spin_lock(&ctx->completion_lock);
@@ -1942,13 +1937,16 @@ static void io_queue_sqe_fallback(struct io_kiocb *req)
 		req->flags &= ~REQ_F_HARDLINK;
 		req->flags |= REQ_F_LINK;
 		io_req_complete_failed(req, req->cqe.res);
-	} else if (unlikely(req->ctx->drain_active)) {
-		io_drain_req(req);
 	} else {
 		int ret = io_req_prep_async(req);
 
-		if (unlikely(ret))
+		if (unlikely(ret)) {
 			io_req_complete_failed(req, ret);
+			return;
+		}
+
+		if (unlikely(req->ctx->drain_active))
+			io_drain_req(req);
 		else
 			io_queue_iowq(req, NULL);
 	}
-- 
2.39.0


  reply	other threads:[~2023-01-29 19:40 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-29 13:26 FAILED: patch "[PATCH] io_uring: always prep_async for drain requests" failed to apply to 6.1-stable tree gregkh
2023-01-29 19:40 ` Jens Axboe [this message]
2023-01-30 10:04   ` Greg KH
2023-01-30 15:05     ` Jens Axboe

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1aa4166f-c66b-5eea-e695-66f206482321@kernel.dk \
    --to=axboe@kernel.dk \
    --cc=dylany@meta.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=stable@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.