From patchwork Tue Aug 9 09:16:29 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ziyang Zhang X-Patchwork-Id: 12939476 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 CA1EDC25B06 for ; Tue, 9 Aug 2022 09:17:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234467AbiHIJR6 (ORCPT ); Tue, 9 Aug 2022 05:17:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44440 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237711AbiHIJRr (ORCPT ); Tue, 9 Aug 2022 05:17:47 -0400 Received: from out30-56.freemail.mail.aliyun.com (out30-56.freemail.mail.aliyun.com [115.124.30.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5852022B3F for ; Tue, 9 Aug 2022 02:17:44 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046056;MF=ziyangzhang@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0VLpL3gB_1660036660; Received: from localhost.localdomain(mailfrom:ZiyangZhang@linux.alibaba.com fp:SMTPD_---0VLpL3gB_1660036660) by smtp.aliyun-inc.com; Tue, 09 Aug 2022 17:17:41 +0800 From: ZiyangZhang To: ming.lei@redhat.com, axboe@kernel.dk Cc: linux-block@vger.kernel.org, xiaoguang.wang@linux.alibaba.com, ZiyangZhang Subject: [PATCH 3/3] ublk_drv: do not add a re-issued request aborted previously to ioucmd's task_work Date: Tue, 9 Aug 2022 17:16:29 +0800 Message-Id: <20220809091629.104682-4-ZiyangZhang@linux.alibaba.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20220809091629.104682-1-ZiyangZhang@linux.alibaba.com> References: <20220809091629.104682-1-ZiyangZhang@linux.alibaba.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org In ublk_queue_rq(), Assume current request is a re-issued request aborted previously in monitor_work because the ubq_daemon(ioucmd's task) is PF_EXITING. For this request, we cannot call io_uring_cmd_complete_in_task() anymore because at that moment io_uring context may be freed in case that no inflight ioucmd exists. Otherwise, we may cause null-deref in ctx->fallback_work. Add a check on UBLK_IO_FLAG_ABORTED to prevent the above situation. This check is safe and makes sense. Note: monitor_work sets UBLK_IO_FLAG_ABORTED and ends this request (releasing the tag). Then the request is restarted(allocating the tag) and we are here. Since releasing/allocating a tag implies smp_mb(), finding UBLK_IO_FLAG_ABORTED guarantees that here is a re-issued request aborted previously. Suggested-by: Ming Lei Signed-off-by: ZiyangZhang --- drivers/block/ublk_drv.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index bedef46f6abf..0b9bd9e02b53 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -725,6 +725,7 @@ static blk_status_t ublk_queue_rq(struct blk_mq_hw_ctx *hctx, { struct ublk_queue *ubq = hctx->driver_data; struct request *rq = bd->rq; + struct ublk_io *io = &ubq->ios[rq->tag]; blk_status_t res; /* fill iod to slot in io cmd buffer */ @@ -748,9 +749,24 @@ static blk_status_t ublk_queue_rq(struct blk_mq_hw_ctx *hctx, if (task_work_add(ubq->ubq_daemon, &data->work, notify_mode)) goto fail; } else { - struct io_uring_cmd *cmd = ubq->ios[rq->tag].cmd; + struct io_uring_cmd *cmd = io->cmd; struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd); + /* + * If the check passes, we know that this is a re-issued request aborted + * previously in monitor_work because the ubq_daemon(cmd's task) is + * PF_EXITING. We cannot call io_uring_cmd_complete_in_task() anymore + * because this ioucmd's io_uring context may be freed now if no inflight + * ioucmd exists. Otherwise we may cause null-deref in ctx->fallback_work. + * + * Note: monitor_work sets UBLK_IO_FLAG_ABORTED and ends this request(releasing + * the tag). Then the request is re-started(allocating the tag) and we are here. + * Since releasing/allocating a tag implies smp_mb(), finding UBLK_IO_FLAG_ABORTED + * guarantees that here is a re-issued request aborted previously. + */ + if ((io->flags & UBLK_IO_FLAG_ABORTED)) + goto fail; + pdu->req = rq; io_uring_cmd_complete_in_task(cmd, ublk_rq_task_work_cb); }