The patch below does not apply to the 6.3-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-6.3.y git checkout FETCH_HEAD git cherry-pick -x ef7dfac51d8ed961b742218f526bd589f3900a59 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023062306-omen-dance-80f0@gregkh' --subject-prefix 'PATCH 6.3.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From ef7dfac51d8ed961b742218f526bd589f3900a59 Mon Sep 17 00:00:00 2001 From: Jens Axboe axboe@kernel.dk Date: Sat, 17 Jun 2023 19:50:24 -0600 Subject: [PATCH] io_uring/poll: serialize poll linked timer start with poll removal

We selectively grab the ctx->uring_lock for poll update/removal, but we really should grab it from the start to fully synchronize with linked timeouts. Normally this is indeed the case, but if requests are forced async by the application, we don't fully cover removal and timer disarm within the uring_lock.

Make this simpler by having consistent locking state for poll removal.

Cc: stable@vger.kernel.org # 6.1+ Reported-by: Querijn Voet querijnqyn@gmail.com Signed-off-by: Jens Axboe axboe@kernel.dk

diff --git a/io_uring/poll.c b/io_uring/poll.c index c90e47dc1e29..a78b8af7d9ab 100644 --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -977,8 +977,9 @@ int io_poll_remove(struct io_kiocb *req, unsigned int issue_flags) struct io_hash_bucket *bucket; struct io_kiocb *preq; int ret2, ret = 0; - struct io_tw_state ts = {}; + struct io_tw_state ts = { .locked = true };

+ io_ring_submit_lock(ctx, issue_flags); preq = io_poll_find(ctx, true, &cd, &ctx->cancel_table, &bucket); ret2 = io_poll_disarm(preq); if (bucket) @@ -990,12 +991,10 @@ int io_poll_remove(struct io_kiocb *req, unsigned int issue_flags) goto out; }

- io_ring_submit_lock(ctx, issue_flags); preq = io_poll_find(ctx, true, &cd, &ctx->cancel_table_locked, &bucket); ret2 = io_poll_disarm(preq); if (bucket) spin_unlock(&bucket->lock); - io_ring_submit_unlock(ctx, issue_flags); if (ret2) { ret = ret2; goto out; @@ -1019,7 +1018,7 @@ found: if (poll_update->update_user_data) preq->cqe.user_data = poll_update->new_user_data;

- ret2 = io_poll_add(preq, issue_flags); + ret2 = io_poll_add(preq, issue_flags & ~IO_URING_F_UNLOCKED); /* successfully updated, don't complete poll request */ if (!ret2 || ret2 == -EIOCBQUEUED) goto out; @@ -1027,9 +1026,9 @@ found:

req_set_fail(preq); io_req_set_res(preq, -ECANCELED, 0); - ts.locked = !(issue_flags & IO_URING_F_UNLOCKED); io_req_task_complete(preq, &ts); out: + io_ring_submit_unlock(ctx, issue_flags); if (ret < 0) { req_set_fail(req); return ret;