The patch below does not apply to the 6.12-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-6.12.y git checkout FETCH_HEAD git cherry-pick -x 84230ad2d2afbf0c44c32967e525c0ad92e26b4e # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025122911-bonding-sampling-8ca0@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 84230ad2d2afbf0c44c32967e525c0ad92e26b4e Mon Sep 17 00:00:00 2001 From: Jens Axboe axboe@kernel.dk Date: Mon, 1 Dec 2025 13:25:22 -0700 Subject: [PATCH] io_uring/poll: correctly handle io_poll_add() return value on update
When the core of io_uring was updated to handle completions consistently and with fixed return codes, the POLL_REMOVE opcode with updates got slightly broken. If a POLL_ADD is pending and then POLL_REMOVE is used to update the events of that request, if that update causes the POLL_ADD to now trigger, then that completion is lost and a CQE is never posted.
Additionally, ensure that if an update does cause an existing POLL_ADD to complete, that the completion value isn't always overwritten with -ECANCELED. For that case, whatever io_poll_add() set the value to should just be retained.
Cc: stable@vger.kernel.org Fixes: 97b388d70b53 ("io_uring: handle completions in the core") Reported-by: syzbot+641eec6b7af1f62f2b99@syzkaller.appspotmail.com Tested-by: syzbot+641eec6b7af1f62f2b99@syzkaller.appspotmail.com Signed-off-by: Jens Axboe axboe@kernel.dk
diff --git a/io_uring/poll.c b/io_uring/poll.c index 8aa4e3a31e73..3f1d716dcfab 100644 --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -937,12 +937,17 @@ int io_poll_remove(struct io_kiocb *req, unsigned int issue_flags)
ret2 = io_poll_add(preq, issue_flags & ~IO_URING_F_UNLOCKED); /* successfully updated, don't complete poll request */ - if (!ret2 || ret2 == -EIOCBQUEUED) + if (ret2 == IOU_ISSUE_SKIP_COMPLETE) goto out; + /* request completed as part of the update, complete it */ + else if (ret2 == IOU_COMPLETE) + goto complete; }
- req_set_fail(preq); io_req_set_res(preq, -ECANCELED, 0); +complete: + if (preq->cqe.res < 0) + req_set_fail(preq); preq->io_task_work.func = io_req_task_complete; io_req_task_work_add(preq); out: