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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 82A99C10F0E for ; Fri, 12 Apr 2019 11:03:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4FB632083E for ; Fri, 12 Apr 2019 11:03:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726867AbfDLLDk (ORCPT ); Fri, 12 Apr 2019 07:03:40 -0400 Received: from mx2.suse.de ([195.135.220.15]:52184 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726711AbfDLLDj (ORCPT ); Fri, 12 Apr 2019 07:03:39 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id A1A14AC84; Fri, 12 Apr 2019 11:03:37 +0000 (UTC) Subject: Re: [PATCH V5 3/9] blk-mq: free hw queue's resource in hctx's release handler To: Ming Lei , Jens Axboe Cc: linux-block@vger.kernel.org, Dongli Zhang , James Smart , Bart Van Assche , linux-scsi@vger.kernel.org, "Martin K . Petersen" , Christoph Hellwig , "James E . J . Bottomley" , jianchao wang , stable@vger.kernel.org References: <20190412033032.10418-1-ming.lei@redhat.com> <20190412033032.10418-4-ming.lei@redhat.com> From: Hannes Reinecke Message-ID: <27ec3b64-1104-236d-bc54-1dbb954da13c@suse.de> Date: Fri, 12 Apr 2019 13:03:35 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190412033032.10418-4-ming.lei@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 4/12/19 5:30 AM, Ming Lei wrote: > Once blk_cleanup_queue() returns, tags shouldn't be used any more, > because blk_mq_free_tag_set() may be called. Commit 45a9c9d909b2 > ("blk-mq: Fix a use-after-free") fixes this issue exactly. > > However, that commit introduces another issue. Before 45a9c9d909b2, > we are allowed to run queue during cleaning up queue if the queue's > kobj refcount is held. After that commit, queue can't be run during > queue cleaning up, otherwise oops can be triggered easily because > some fields of hctx are freed by blk_mq_free_queue() in blk_cleanup_queue(). > > We have invented ways for addressing this kind of issue before, such as: > > 8dc765d438f1 ("SCSI: fix queue cleanup race before queue initialization is done") > c2856ae2f315 ("blk-mq: quiesce queue before freeing queue") > > But still can't cover all cases, recently James reports another such > kind of issue: > > https://marc.info/?l=linux-scsi&m=155389088124782&w=2 > > This issue can be quite hard to address by previous way, given > scsi_run_queue() may run requeues for other LUNs. > > Fixes the above issue by freeing hctx's resources in its release handler, and this > way is safe becasue tags isn't needed for freeing such hctx resource. > > This approach follows typical design pattern wrt. kobject's release handler. > > Cc: Dongli Zhang > Cc: James Smart > Cc: Bart Van Assche > Cc: linux-scsi@vger.kernel.org, > Cc: Martin K . Petersen , > Cc: Christoph Hellwig , > Cc: James E . J . Bottomley , > Cc: jianchao wang > Reported-by: James Smart > Fixes: 45a9c9d909b2 ("blk-mq: Fix a use-after-free") > Cc: stable@vger.kernel.org > Signed-off-by: Ming Lei > --- > block/blk-core.c | 2 +- > block/blk-mq-sysfs.c | 6 ++++++ > block/blk-mq.c | 8 ++------ > block/blk-mq.h | 2 +- > 4 files changed, 10 insertions(+), 8 deletions(-) > > diff --git a/block/blk-core.c b/block/blk-core.c > index 6583d67f3e34..20298aa5a77c 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -374,7 +374,7 @@ void blk_cleanup_queue(struct request_queue *q) > blk_exit_queue(q); > > if (queue_is_mq(q)) > - blk_mq_free_queue(q); > + blk_mq_exit_queue(q); > > percpu_ref_exit(&q->q_usage_counter); > > diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c > index 3f9c3f4ac44c..4040e62c3737 100644 > --- a/block/blk-mq-sysfs.c > +++ b/block/blk-mq-sysfs.c > @@ -10,6 +10,7 @@ > #include > > #include > +#include "blk.h" > #include "blk-mq.h" > #include "blk-mq-tag.h" > > @@ -33,6 +34,11 @@ static void blk_mq_hw_sysfs_release(struct kobject *kobj) > { > struct blk_mq_hw_ctx *hctx = container_of(kobj, struct blk_mq_hw_ctx, > kobj); > + > + if (hctx->flags & BLK_MQ_F_BLOCKING) > + cleanup_srcu_struct(hctx->srcu); > + blk_free_flush_queue(hctx->fq); > + sbitmap_free(&hctx->ctx_map); > free_cpumask_var(hctx->cpumask); > kfree(hctx->ctxs); > kfree(hctx); > diff --git a/block/blk-mq.c b/block/blk-mq.c > index b512ba0cb359..afc9912e2e42 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -2259,12 +2259,7 @@ static void blk_mq_exit_hctx(struct request_queue *q, > if (set->ops->exit_hctx) > set->ops->exit_hctx(hctx, hctx_idx); > > - if (hctx->flags & BLK_MQ_F_BLOCKING) > - cleanup_srcu_struct(hctx->srcu); > - > blk_mq_remove_cpuhp(hctx); > - blk_free_flush_queue(hctx->fq); > - sbitmap_free(&hctx->ctx_map); > } > > static void blk_mq_exit_hw_queues(struct request_queue *q, > @@ -2899,7 +2894,8 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, > } > EXPORT_SYMBOL(blk_mq_init_allocated_queue); > > -void blk_mq_free_queue(struct request_queue *q) > +/* tags can _not_ be used after returning from blk_mq_exit_queue */ > +void blk_mq_exit_queue(struct request_queue *q) > { > struct blk_mq_tag_set *set = q->tag_set; > > diff --git a/block/blk-mq.h b/block/blk-mq.h > index d704fc7766f4..c421e3a16e36 100644 > --- a/block/blk-mq.h > +++ b/block/blk-mq.h > @@ -37,7 +37,7 @@ struct blk_mq_ctx { > struct kobject kobj; > } ____cacheline_aligned_in_smp; > > -void blk_mq_free_queue(struct request_queue *q); > +void blk_mq_exit_queue(struct request_queue *q); > int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr); > void blk_mq_wake_waiters(struct request_queue *q); > bool blk_mq_dispatch_rq_list(struct request_queue *, struct list_head *, bool); > Hmm. While this is a good point, I'm somehow not convinced that it fixes the mentioned problem. For the sbitmap_any_set() case, the problem appears to be the racy interaction between nvme_scan_queues() and nvme_reset_ctrl(). Both can (and do) run in parallel, and as nvme_scan_queue() is not able to update the nvme namespace list race-free (nvme_ns_remove() will kill the namespace before removing it from the queue) we'll hit issues where nvme_start_queues() is called on namespaces which are halfway through nvme_ns_remove(), causing all sorts of issues. See "[PATCHv2 RFC] nvme: use nvme_set_queue_dying() during namespace rescanning" for my attempt to fix this. That patch is actually not complete; there is another one under testing currently to not remove namespaces at all during nvme_reset_ctrl(), but results are not in yet. Otherwise: Reviewed-by: Hannes Reinecke Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking hare@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 21284 (AG Nürnberg)