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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 0E794C282CE for ; Sat, 13 Apr 2019 07:18:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D960F21721 for ; Sat, 13 Apr 2019 07:18:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726457AbfDMHSq (ORCPT ); Sat, 13 Apr 2019 03:18:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34462 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726285AbfDMHSq (ORCPT ); Sat, 13 Apr 2019 03:18:46 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B385681F0D; Sat, 13 Apr 2019 07:18:45 +0000 (UTC) Received: from ming.t460p (ovpn-8-18.pek2.redhat.com [10.72.8.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 50D6A19C7C; Sat, 13 Apr 2019 07:18:35 +0000 (UTC) Date: Sat, 13 Apr 2019 15:18:31 +0800 From: Ming Lei To: Hannes Reinecke Cc: Jens Axboe , 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 Subject: Re: [PATCH V5 3/9] blk-mq: free hw queue's resource in hctx's release handler Message-ID: <20190413071829.GB9108@ming.t460p> References: <20190412033032.10418-1-ming.lei@redhat.com> <20190412033032.10418-4-ming.lei@redhat.com> <27ec3b64-1104-236d-bc54-1dbb954da13c@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <27ec3b64-1104-236d-bc54-1dbb954da13c@suse.de> User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Sat, 13 Apr 2019 07:18:45 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Fri, Apr 12, 2019 at 01:03:35PM +0200, Hannes Reinecke wrote: > 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. This patch fixes the following generic issue in block layer: 1) usually any block layer API may be called safely when the request queue's refcount is held 2) when blk_cleanup_queue() is run, no use-after-free oops can be triggered on the code path in 1) > > 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. This is one race between nvme reset and scan, and especially the refcount of ns queue isn't held before calling nvme_stop_queues() and nvme_start_queues(). The above situation is one NVMe specific issue and doesn't belong to what this patch tries to address. > > 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: Looks the above 'Otherwise' shouldn't be needed, as I explained. > > Reviewed-by: Hannes Reinecke Thanks! -- Ming