From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57FEFC433F5 for ; Tue, 17 May 2022 23:52:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232169AbiEQXwl (ORCPT ); Tue, 17 May 2022 19:52:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43610 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232142AbiEQXwj (ORCPT ); Tue, 17 May 2022 19:52:39 -0400 Received: from mail-pj1-x102f.google.com (mail-pj1-x102f.google.com [IPv6:2607:f8b0:4864:20::102f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 85A3853B6D for ; Tue, 17 May 2022 16:52:36 -0700 (PDT) Received: by mail-pj1-x102f.google.com with SMTP id ev18so349138pjb.4 for ; Tue, 17 May 2022 16:52:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20210112.gappssmtp.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:content-language:to :cc:references:from:in-reply-to:content-transfer-encoding; bh=XJTnzIVwKKP2159kKSUS1BPKhBYNJeW8HbtdFHHy4iE=; b=btuV0tJiD7pGnwKvvbQErl6mxwh+SGFL78yB20r9JCvzvaP0zYwMvi4eaThuEoUsWF Xn4xx6FDgnx/IOoCtz1gqtpTGNB1wYzQinlYEVBXxglHhnXk0mxRlOupN7YcygC6hRM2 KQ74U/Gfi233jnL+9r7E/9oRStOt6eTTP2if+vBdD8ikLIzTx8UuNa/4e6+lgZlW0X4j GzIzF0li7U0IGfSYGTxtDNS4PTbYOt/ELyiNfED6iXwEaMYcYlZrqAB4IWTOfO1XZKQL IIe7bRFfukTOjX4IvefuxbO2fsVPu829r8+0g89NKQC6FDYbl5f+lyQ0eAHdcXeLeGfY JR/A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=XJTnzIVwKKP2159kKSUS1BPKhBYNJeW8HbtdFHHy4iE=; b=TkEI86EGMZMIMRBrinQGr7qcZxcq30tz805a72cabPbs3oGX8zVBYldofKzEQhQ5H+ yUV5TXYoSGD15oJ3MIHX/WsFYyw6b35LzSi3oOn2YLKJ4q05JEgU8XzN41r7qvcnvDv9 pN7niWv0ZRS8FSX6pBT2h69B8e5X09u4iO2nH8gSyjlho3ntL9VoLDMSwg9bsbwo0ILp T0QSYVm6W/DbYQjXhMWYC8COah3yyKuJF+FAXABwTESRjauWw2Jfv3iOByJGrkLECAXB /jNE0fiETVp44xOA9IIkTMwy19NLE1ZUK/KMS1DFtDrVQoURNdNZ8tafecAQstOUcst3 r96Q== X-Gm-Message-State: AOAM532SJB93S4kHDzd2ycmaJCu1F5uP6EuMaaYGwOd085Dp/GEcpgzD ukLumsadjVtYiaMLOGckLJS1Pg== X-Google-Smtp-Source: ABdhPJxBuUJ6jRQmUBj89KENzVfnvjJ/Pw/8kwPGKN6UP+F2fpjWv0AMGDAtFKMAQU9QdMbf2FwdGA== X-Received: by 2002:a17:902:e948:b0:15e:cd79:2a1a with SMTP id b8-20020a170902e94800b0015ecd792a1amr24409818pll.109.1652831555862; Tue, 17 May 2022 16:52:35 -0700 (PDT) Received: from [192.168.1.100] ([198.8.77.157]) by smtp.gmail.com with ESMTPSA id iz15-20020a170902ef8f00b001619b38701bsm186571plb.72.2022.05.17.16.52.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 17 May 2022 16:52:35 -0700 (PDT) Message-ID: Date: Tue, 17 May 2022 17:52:33 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [REPORT] Use-after-free Read in __fdget_raw in v5.10.y Content-Language: en-US To: Lee Jones Cc: Pavel Begunkov , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: <97cba3e1-4ef7-0a17-8456-e0787d6702c6@kernel.dk> <3d271554-9ddc-07ad-3ff8-30aba31f8bf2@kernel.dk> From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/17/22 7:00 AM, Lee Jones wrote: > On Tue, 17 May 2022, Jens Axboe wrote: > >> On 5/17/22 6:36 AM, Lee Jones wrote: >>> On Tue, 17 May 2022, Jens Axboe wrote: >>> >>>> On 5/17/22 6:24 AM, Lee Jones wrote: >>>>> On Tue, 17 May 2022, Jens Axboe wrote: >>>>> >>>>>> On 5/17/22 5:41 AM, Lee Jones wrote: >>>>>>> Good afternoon Jens, Pavel, et al., >>>>>>> >>>>>>> Not sure if you are presently aware, but there appears to be a >>>>>>> use-after-free issue affecting the io_uring worker driver (fs/io-wq.c) >>>>>>> in Stable v5.10.y. >>>>>>> >>>>>>> The full sysbot report can be seen below [0]. >>>>>>> >>>>>>> The C-reproducer has been placed below that [1]. >>>>>>> >>>>>>> I had great success running this reproducer in an infinite loop. >>>>>>> >>>>>>> My colleague reverse-bisected the fixing commit to: >>>>>>> >>>>>>> commit fb3a1f6c745ccd896afadf6e2d6f073e871d38ba >>>>>>> Author: Jens Axboe >>>>>>> Date: Fri Feb 26 09:47:20 2021 -0700 >>>>>>> >>>>>>> io-wq: have manager wait for all workers to exit >>>>>>> >>>>>>> Instead of having to wait separately on workers and manager, just have >>>>>>> the manager wait on the workers. We use an atomic_t for the reference >>>>>>> here, as we need to start at 0 and allow increment from that. Since the >>>>>>> number of workers is naturally capped by the allowed nr of processes, >>>>>>> and that uses an int, there is no risk of overflow. >>>>>>> >>>>>>> Signed-off-by: Jens Axboe >>>>>>> >>>>>>> fs/io-wq.c | 30 ++++++++++++++++++++++-------- >>>>>>> 1 file changed, 22 insertions(+), 8 deletions(-) >>>>>> >>>>>> Does this fix it: >>>>>> >>>>>> commit 886d0137f104a440d9dfa1d16efc1db06c9a2c02 >>>>>> Author: Jens Axboe >>>>>> Date: Fri Mar 5 12:59:30 2021 -0700 >>>>>> >>>>>> io-wq: fix race in freeing 'wq' and worker access >>>>>> >>>>>> Looks like it didn't make it into 5.10-stable, but we can certainly >>>>>> rectify that. >>>>> >>>>> Thanks for your quick response Jens. >>>>> >>>>> This patch doesn't apply cleanly to v5.10.y. >>>> >>>> This is probably why it never made it into 5.10-stable :-/ >>> >>> Right. It doesn't apply at all unfortunately. >>> >>>>> I'll have a go at back-porting it. Please bear with me. >>>> >>>> Let me know if you into issues with that and I can help out. >>> >>> I think the dependency list is too big. >>> >>> Too much has changed that was never back-ported. >>> >>> Actually the list of patches pertaining to fs/io-wq.c alone isn't so >>> bad, I did start to back-port them all but some of the big ones have >>> fs/io_uring.c changes incorporated and that list is huge (256 patches >>> from v5.10 to the fixing patch mentioned above). >> >> The problem is that 5.12 went to the new worker setup, and this patch >> landed after that even though it also applies to the pre-native workers. >> Hence the dependency chain isn't really as long as it seems, probably >> just a few patches backporting the change references and completions. >> >> I'll take a look this afternoon. > > Thanks Jens. I really appreciate it. Can you see if this helps? Untested... diff --git a/fs/io-wq.c b/fs/io-wq.c index 3d5fc76b92d0..35af489bcaf6 100644 --- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -125,6 +125,9 @@ struct io_wq { refcount_t refs; struct completion done; + atomic_t worker_refs; + struct completion worker_done; + struct hlist_node cpuhp_node; refcount_t use_refs; @@ -250,8 +253,8 @@ static void io_worker_exit(struct io_worker *worker) raw_spin_unlock_irq(&wqe->lock); kfree_rcu(worker, rcu); - if (refcount_dec_and_test(&wqe->wq->refs)) - complete(&wqe->wq->done); + if (atomic_dec_and_test(&wqe->wq->worker_refs)) + complete(&wqe->wq->worker_done); } static inline bool io_wqe_run_queue(struct io_wqe *wqe) @@ -695,9 +698,13 @@ static bool create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index) worker->wqe = wqe; spin_lock_init(&worker->lock); + atomic_inc(&wq->worker_refs); + worker->task = kthread_create_on_node(io_wqe_worker, worker, wqe->node, "io_wqe_worker-%d/%d", index, wqe->node); if (IS_ERR(worker->task)) { + if (atomic_dec_and_test(&wq->worker_refs)) + complete(&wq->worker_done); kfree(worker); return false; } @@ -717,7 +724,6 @@ static bool create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index) if (index == IO_WQ_ACCT_UNBOUND) atomic_inc(&wq->user->processes); - refcount_inc(&wq->refs); wake_up_process(worker->task); return true; } @@ -822,17 +828,18 @@ static int io_wq_manager(void *data) task_work_run(); out: - if (refcount_dec_and_test(&wq->refs)) { - complete(&wq->done); - return 0; - } /* if ERROR is set and we get here, we have workers to wake */ - if (test_bit(IO_WQ_BIT_ERROR, &wq->state)) { - rcu_read_lock(); - for_each_node(node) - io_wq_for_each_worker(wq->wqes[node], io_wq_worker_wake, NULL); - rcu_read_unlock(); - } + rcu_read_lock(); + for_each_node(node) + io_wq_for_each_worker(wq->wqes[node], io_wq_worker_wake, NULL); + rcu_read_unlock(); + + if (atomic_read(&wq->worker_refs)) + wait_for_completion(&wq->worker_done); + + if (refcount_dec_and_test(&wq->refs)) + complete(&wq->done); + return 0; } @@ -1135,6 +1142,9 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data) init_completion(&wq->done); + init_completion(&wq->worker_done); + atomic_set(&wq->worker_refs, 0); + wq->manager = kthread_create(io_wq_manager, wq, "io_wq_manager"); if (!IS_ERR(wq->manager)) { wake_up_process(wq->manager); @@ -1179,11 +1189,6 @@ static void __io_wq_destroy(struct io_wq *wq) if (wq->manager) kthread_stop(wq->manager); - rcu_read_lock(); - for_each_node(node) - io_wq_for_each_worker(wq->wqes[node], io_wq_worker_wake, NULL); - rcu_read_unlock(); - wait_for_completion(&wq->done); for_each_node(node) -- Jens Axboe