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Mon, 19 Jan 2026 18:56:47 -0800 (PST) Received: from [192.168.1.150] ([198.8.77.157]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-4044bd150dasm8268481fac.14.2026.01.19.18.56.46 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 19 Jan 2026 18:56:46 -0800 (PST) Message-ID: <7efcfd5a-d00d-4dea-b69a-0be272057946@kernel.dk> Date: Mon, 19 Jan 2026 19:56:45 -0700 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US To: io-uring From: Jens Axboe Subject: [PATCH] io_uring/waitid: fix KCSAN warning on io_waitid->head Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Storing of the iw->head entry inside the wait_queue callback, or when removing a waitid item, really should use proper load/store acquire/release semantics, and KCSAN correctly warns of that. Ensure that they do so. Reported-by: syzbot+eb441775f4f948a0902f@syzkaller.appspotmail.com Fixes: a48c0cbf28c0 ("io_uring/waitid: have io_waitid_complete() remove wait queue entry") Signed-off-by: Jens Axboe --- Introduced in 6.19, queued in io_uring-6.19. diff --git a/io_uring/waitid.c b/io_uring/waitid.c index 2d4cbd47c67c..d25d60aed6af 100644 --- a/io_uring/waitid.c +++ b/io_uring/waitid.c @@ -114,11 +114,11 @@ static void io_waitid_remove_wq(struct io_kiocb *req) struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); struct wait_queue_head *head; - head = READ_ONCE(iw->head); + head = smp_load_acquire(&iw->head); if (head) { struct io_waitid_async *iwa = req->async_data; - iw->head = NULL; + smp_store_release(&iw->head, NULL); spin_lock_irq(&head->lock); list_del_init(&iwa->wo.child_wait.entry); spin_unlock_irq(&head->lock); @@ -246,7 +246,7 @@ static int io_waitid_wait(struct wait_queue_entry *wait, unsigned mode, return 0; list_del_init(&wait->entry); - iw->head = NULL; + smp_store_release(&iw->head, NULL); /* cancel is in progress */ if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK) -- Jens Axboe