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.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x d63b0e8a628e62ca85a0f7915230186bb92f8bb4 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025021131-mushy-affecting-a576@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From d63b0e8a628e62ca85a0f7915230186bb92f8bb4 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov asml.silence@gmail.com Date: Tue, 28 Jan 2025 00:55:24 +0000 Subject: [PATCH] io_uring: fix multishots with selected buffers

We do io_kbuf_recycle() when arming a poll but every iteration of a multishot can grab more buffers, which is why we need to flush the kbuf ring state before continuing with waiting.

Cc: stable@vger.kernel.org Fixes: b3fdea6ecb55c ("io_uring: multishot recv") Reported-by: Muhammad Ramdhan ramdhan@starlabs.sg Reported-by: Bing-Jhong Billy Jheng billy@starlabs.sg Reported-by: Jacob Soo jacob.soo@starlabs.sg Signed-off-by: Pavel Begunkov asml.silence@gmail.com Link: https://lore.kernel.org/r/1bfc9990fe435f1fc6152ca9efeba5eb3e68339c.173802557... Signed-off-by: Jens Axboe axboe@kernel.dk

diff --git a/io_uring/poll.c b/io_uring/poll.c index 356474c66f32..31b118133bb0 100644 --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -315,8 +315,10 @@ void io_poll_task_func(struct io_kiocb *req, struct io_tw_state *ts)

ret = io_poll_check_events(req, ts); if (ret == IOU_POLL_NO_ACTION) { + io_kbuf_recycle(req, 0); return; } else if (ret == IOU_POLL_REQUEUE) { + io_kbuf_recycle(req, 0); __io_poll_execute(req, 0); return; }