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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 C4AC1C11D00 for ; Fri, 21 Feb 2020 03:05:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 98FFA208CD for ; Fri, 21 Feb 2020 03:05:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729371AbgBUDFZ (ORCPT ); Thu, 20 Feb 2020 22:05:25 -0500 Received: from szxga07-in.huawei.com ([45.249.212.35]:57364 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729280AbgBUDFY (ORCPT ); Thu, 20 Feb 2020 22:05:24 -0500 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 9E4FE2056280458B762B; Fri, 21 Feb 2020 11:05:22 +0800 (CST) Received: from [10.173.220.74] (10.173.220.74) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.439.0; Fri, 21 Feb 2020 11:05:13 +0800 Subject: Re: [PATCH 1/4] block: fix use-after-free on cached last_lookup partition To: Ming Lei , Jens Axboe CC: , Christoph Hellwig , "Hou Tao" References: <20200109062109.2313-1-ming.lei@redhat.com> <20200109062109.2313-2-ming.lei@redhat.com> From: Yufen Yu Message-ID: Date: Fri, 21 Feb 2020 11:05:13 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <20200109062109.2313-2-ming.lei@redhat.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.173.220.74] X-CFilter-Loop: Reflected Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hi Guys, Did this patch have been forgotten? So, ping... Thanks, Yufen On 2020/1/9 14:21, Ming Lei wrote: > delete_partition() clears the cached last_lookup partition. However > the .last_lookup cache may be overwritten by one IO path after > it is cleared from delete_partition(). Then another IO path may > use the cached deleting partition after __delete_partition() is > called, then use-after-free is triggered on the cached partition. > > Fixes the issue by the following approach: > > 1) always get the partition's refcount via hd_struct_try_get() before > setting .last_lookup > > 2) move clearing .last_lookup from delete_partition() to > __delete_partition() which is release handle of the partition's > percpu-refcount, so that no IO path can overwrite .last_lookup after it > is cleared in __delete_partition(). > > It is one candidate approach of Yufen's patch[1] which adds overhead > in fast path by indirect lookup which may introduce one extra cacheline > in IO path. Also this patch relies on percpu-refcount's protection, and > it is easier to understand and verify. > > [1] https://lore.kernel.org/linux-block/20200109013551.GB9655@ming.t460p/T/#t > > Reported-by: Yufen Yu > Cc: Christoph Hellwig > Cc: Hou Tao > Signed-off-by: Ming Lei > --- > block/blk-core.c | 12 ------------ > block/genhd.c | 6 +++++- > block/partition-generic.c | 10 +++++++++- > include/linux/genhd.h | 1 + > 4 files changed, 15 insertions(+), 14 deletions(-) > > diff --git a/block/blk-core.c b/block/blk-core.c > index 089e890ab208..79599f5fd5b7 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -1365,18 +1365,6 @@ void blk_account_io_start(struct request *rq, bool new_io) > part_stat_inc(part, merges[rw]); > } else { > part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq)); > - if (!hd_struct_try_get(part)) { > - /* > - * The partition is already being removed, > - * the request will be accounted on the disk only > - * > - * We take a reference on disk->part0 although that > - * partition will never be deleted, so we can treat > - * it as any other partition. > - */ > - part = &rq->rq_disk->part0; > - hd_struct_get(part); > - } > part_inc_in_flight(rq->q, part, rw); > rq->part = part; > } > diff --git a/block/genhd.c b/block/genhd.c > index ff6268970ddc..6029c94510f0 100644 > --- a/block/genhd.c > +++ b/block/genhd.c > @@ -286,17 +286,21 @@ struct hd_struct *disk_map_sector_rcu(struct gendisk *disk, sector_t sector) > ptbl = rcu_dereference(disk->part_tbl); > > part = rcu_dereference(ptbl->last_lookup); > - if (part && sector_in_part(part, sector)) > + if (part && sector_in_part(part, sector) && hd_struct_try_get(part)) > return part; > > for (i = 1; i < ptbl->len; i++) { > part = rcu_dereference(ptbl->part[i]); > > if (part && sector_in_part(part, sector)) { > + if (!hd_struct_try_get(part)) > + goto exit; > rcu_assign_pointer(ptbl->last_lookup, part); > return part; > } > } > + exit: > + hd_struct_get(&disk->part0); > return &disk->part0; > } > EXPORT_SYMBOL_GPL(disk_map_sector_rcu); > diff --git a/block/partition-generic.c b/block/partition-generic.c > index 1d20c9cf213f..1739f750dbf2 100644 > --- a/block/partition-generic.c > +++ b/block/partition-generic.c > @@ -262,6 +262,12 @@ static void delete_partition_work_fn(struct work_struct *work) > void __delete_partition(struct percpu_ref *ref) > { > struct hd_struct *part = container_of(ref, struct hd_struct, ref); > + struct disk_part_tbl *ptbl = > + rcu_dereference_protected(part->disk->part_tbl, 1); > + > + rcu_assign_pointer(ptbl->last_lookup, NULL); > + put_device(disk_to_dev(part->disk)); > + > INIT_RCU_WORK(&part->rcu_work, delete_partition_work_fn); > queue_rcu_work(system_wq, &part->rcu_work); > } > @@ -283,8 +289,9 @@ void delete_partition(struct gendisk *disk, int partno) > if (!part) > return; > > + get_device(disk_to_dev(disk)); > rcu_assign_pointer(ptbl->part[partno], NULL); > - rcu_assign_pointer(ptbl->last_lookup, NULL); > + > kobject_put(part->holder_dir); > device_del(part_to_dev(part)); > > @@ -349,6 +356,7 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno, > p->nr_sects = len; > p->partno = partno; > p->policy = get_disk_ro(disk); > + p->disk = disk; > > if (info) { > struct partition_meta_info *pinfo = alloc_part_info(disk); > diff --git a/include/linux/genhd.h b/include/linux/genhd.h > index 8bb63027e4d6..1b09cfe00aa3 100644 > --- a/include/linux/genhd.h > +++ b/include/linux/genhd.h > @@ -130,6 +130,7 @@ struct hd_struct { > struct disk_stats dkstats; > #endif > struct percpu_ref ref; > + struct gendisk *disk; > struct rcu_work rcu_work; > }; > >