This is a note to let you know that I've just added the patch titled
io_uring: disallow self-propelled ring polling
to the 6.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
io_uring-disallow-self-propelled-ring-polling.patch
and it can be found in the queue-6.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7fdbc5f014c3f71bc44673a2d6c5bb2d12d45f25 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@xxxxxxxxx>
Date: Fri, 18 Nov 2022 15:41:41 +0000
Subject: io_uring: disallow self-propelled ring polling
From: Pavel Begunkov <asml.silence@xxxxxxxxx>
commit 7fdbc5f014c3f71bc44673a2d6c5bb2d12d45f25 upstream.
When we post a CQE we wake all ring pollers as it normally should be.
However, if a CQE was generated by a multishot poll request targeting
its own ring, it'll wake that request up, which will make it to post
a new CQE, which will wake the request and so on until it exhausts all
CQ entries.
Don't allow multishot polling io_uring files but downgrade them to
oneshots, which was always stated as a correct behaviour that the
userspace should check for.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: aa43477b04025 ("io_uring: poll rework")
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Link: https://lore.kernel.org/r/3124038c0e7474d427538c2d915335ec28c92d21.1668785722.git.asml.silence@xxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
io_uring/poll.c | 2 ++
1 file changed, 2 insertions(+)
--- a/io_uring/poll.c
+++ b/io_uring/poll.c
@@ -244,6 +244,8 @@ static int io_poll_check_events(struct i
continue;
if (req->apoll_events & EPOLLONESHOT)
return IOU_POLL_DONE;
+ if (io_is_uring_fops(req->file))
+ return IOU_POLL_DONE;
/* multishot, just fill a CQE and proceed */
if (!(req->flags & REQ_F_APOLL_MULTISHOT)) {
Patches currently in stable-queue which might be from asml.silence@xxxxxxxxx are
queue-6.0/io_uring-update-res-mask-in-io_poll_check_events.patch
queue-6.0/io_uring-fix-multishot-recv-request-leaks.patch
queue-6.0/io_uring-fix-tw-losing-poll-events.patch
queue-6.0/io_uring-fix-multishot-accept-request-leaks.patch
queue-6.0/io_uring-poll-fix-double-poll-req-flags-races.patch
queue-6.0/io_uring-disallow-self-propelled-ring-polling.patch
