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 X-Spam-Level: X-Spam-Status: No, score=-9.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BB1DAC43461 for ; Tue, 15 Sep 2020 12:21:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6817B2078E for ; Tue, 15 Sep 2020 12:21:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="YRWqNhGW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726371AbgIOMVS (ORCPT ); Tue, 15 Sep 2020 08:21:18 -0400 Received: from mail29.static.mailgun.info ([104.130.122.29]:51442 "EHLO mail29.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726068AbgIOMVJ (ORCPT ); Tue, 15 Sep 2020 08:21:09 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1600172446; h=Message-ID: References: In-Reply-To: Subject: Cc: To: From: Date: Content-Transfer-Encoding: Content-Type: MIME-Version: Sender; bh=4O44pOtYOK/VYrXaUZ5IWqJuK/oO3/HRyOsnRwhqfP4=; b=YRWqNhGWUf3MvmbHIdPebiQg0cwehcjdauHJf1u3qFUkC27HWveU6GIiZP8t0cQukZu0LLBm +yWjka2v+D1lBFhsfScG06yUp92z6PqdzZ+sVFLRmNZAqamq51O7vIqKPSXhK+C8PwraH2+R FWxnARHA28goviDV9JjwJUM7irA= X-Mailgun-Sending-Ip: 104.130.122.29 X-Mailgun-Sid: WyI0MmE5NyIsICJsaW51eC1ibG9ja0B2Z2VyLmtlcm5lbC5vcmciLCAiYmU5ZTRhIl0= Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n04.prod.us-west-2.postgun.com with SMTP id 5f60b1927f21d51b308ab98e (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Tue, 15 Sep 2020 12:20:34 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 1604BC433CA; Tue, 15 Sep 2020 12:20:34 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: ppvk) by smtp.codeaurora.org (Postfix) with ESMTPSA id 2D9C1C433C8; Tue, 15 Sep 2020 12:20:33 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Tue, 15 Sep 2020 17:50:33 +0530 From: ppvk@codeaurora.org To: Ming Lei Cc: axboe@kernel.dk, linux-block@vger.kernel.org, stummala@codeaurora.org, sayalil@codeaurora.org Subject: Re: [PATCH V2] block: Fix use-after-free issue while accessing ioscheduler lock In-Reply-To: <20200915100908.GA764869@T590> References: <1600161062-43793-1-git-send-email-ppvk@codeaurora.org> <20200915100908.GA764869@T590> Message-ID: <38dad0eb6f1d719fc877f24cc42902ef@codeaurora.org> X-Sender: ppvk@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2020-09-15 15:39, Ming Lei wrote: > On Tue, Sep 15, 2020 at 02:41:02PM +0530, Pradeep P V K wrote: >> Observes below crash while accessing (use-after-free) lock member >> of bfq data. >> >> context#1 context#2 >> process_one_work() >> kthread() blk_mq_run_work_fn() >> worker_thread() ->__blk_mq_run_hw_queue() >> process_one_work() ->blk_mq_sched_dispatch_requests() >> __blk_release_queue() ->blk_mq_do_dispatch_sched() > > Just found __blk_release_queue killed in v5.9 cycle. > Yes on v5.9 blk_release_queue() will be called directly by q->kobj when request_queue ref. goes zero but where as on older kernel versions (< 5.9), blk_release_queue() will schedule a work to invoke/call "__blk_release_queue()". >> ->__elevator_exit() >> ->blk_mq_exit_sched() >> ->exit_sched() >> ->kfree() >> ->bfq_dispatch_request() >> ->spin_unlock_irq(&bfqd->lock) > > Actually not sure if the above race is easy to trigger in recent > kernel, > because we do call cancel_delayed_work_sync() in > blk_mq_hw_sysfs_release(), > which is usually called before __elevator_exit() from > blk_exit_queue()/blk_release_queue(). > blk_mq_hw_sysfs_release() will be called from blk_mq_release() i.e. with kobject_put(hctx->kobj), which is after __elevator_exit() __elevator_exit() is called from blk_exit_queue() which is prior to blk_mq_release(). > So can you share your kernel version in which the issue is reproduced? > And can you reproduce this issue on v5.8 or v5.9-rc5? > This issue is seen on v5.4 stable and it is very easy to reproduce on v5.4. sorry, i don't have a resource with v5.8 or with latest kernel. I can help you to get tested on v5.4. From the issue prospective, both v5.4 kernel and latest kernels calls blk_mq_release() -> blk_mq_hw_sysfs_release() after __elevator_exit(). So, i think it wont matter much here. >> >> This is because of the kblockd delayed work that might got scheduled >> around blk_release_queue() and accessed use-after-free member of >> bfq_data. >> >> 240.212359: <2> Unable to handle kernel paging request at >> virtual address ffffffee2e33ad70 >> ... >> 240.212637: <2> Workqueue: kblockd blk_mq_run_work_fn >> 240.212649: <2> pstate: 00c00085 (nzcv daIf +PAN +UAO) >> 240.212666: <2> pc : queued_spin_lock_slowpath+0x10c/0x2e0 >> 240.212677: <2> lr : queued_spin_lock_slowpath+0x84/0x2e0 >> ... >> Call trace: >> 240.212865: <2> queued_spin_lock_slowpath+0x10c/0x2e0 >> 240.212876: <2> do_raw_spin_lock+0xf0/0xf4 >> 240.212890: <2> _raw_spin_lock_irq+0x74/0x94 >> 240.212906: <2> bfq_dispatch_request+0x4c/0xd60 >> 240.212918: <2> blk_mq_do_dispatch_sched+0xe0/0x1f0 >> 240.212927: <2> blk_mq_sched_dispatch_requests+0x130/0x194 >> 240.212940: <2> __blk_mq_run_hw_queue+0x100/0x158 >> 240.212950: <2> blk_mq_run_work_fn+0x1c/0x28 >> 240.212963: <2> process_one_work+0x280/0x460 >> 240.212973: <2> worker_thread+0x27c/0x4dc >> 240.212986: <2> kthread+0x160/0x170 >> >> Fix this by cancelling the delayed work if any before elevator exits. >> >> Changes since V1: >> - Moved the logic into blk_cleanup_queue() as per Ming comments. >> >> Signed-off-by: Pradeep P V K >> --- >> block/blk-mq.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/block/blk-mq.c b/block/blk-mq.c >> index 4abb714..890fded 100644 >> --- a/block/blk-mq.c >> +++ b/block/blk-mq.c >> @@ -2598,6 +2598,7 @@ static void blk_mq_exit_hw_queues(struct >> request_queue *q, >> break; >> blk_mq_debugfs_unregister_hctx(hctx); >> blk_mq_exit_hctx(q, set, hctx, i); >> + cancel_delayed_work_sync(&hctx->run_work); >> } >> } > > It should be better to move cancel_delayed_work_sync() into > blk_mq_exit_hctx(), exactly before adding hctx into unused list. > Sure. i will do it in my next patch series. > > Thanks, > Ming Thanks and Regards, Pradeep