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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 B952BC38A24 for ; Thu, 7 May 2020 08:53:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 955FA2073A for ; Thu, 7 May 2020 08:53:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="V/G1sPjS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725848AbgEGIxC (ORCPT ); Thu, 7 May 2020 04:53:02 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:20241 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725802AbgEGIxB (ORCPT ); Thu, 7 May 2020 04:53:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588841579; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tpA0pdi0rYGUd0QecsXouuj41dAKhFaGvzGLf3JXxQ0=; b=V/G1sPjSn/dzKmTht28IxDcI5tl88Ywu6uKpPsqHQb/Rbdv8IqfL25HUg1YePde7M0+6He eEhpIUIghEiIxD3UBjaTktCd55soKseN1k1BKuwO7+0fDeD6mq5WMqqfkVMvYaWBZp5SR+ U/48wW62qJLMOcNCdvU8b4S1GNMVLpY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-111-IupDrj-dPP2WbFctXVsxOw-1; Thu, 07 May 2020 04:52:56 -0400 X-MC-Unique: IupDrj-dPP2WbFctXVsxOw-1 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id CD6841895A29; Thu, 7 May 2020 08:52:54 +0000 (UTC) Received: from localhost (ovpn-8-38.pek2.redhat.com [10.72.8.38]) by smtp.corp.redhat.com (Postfix) with ESMTP id 075C21FBCD; Thu, 7 May 2020 08:52:53 +0000 (UTC) From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, Ming Lei , Yufen Yu , Christoph Hellwig , Hou Tao Subject: [PATCH 1/4] block: fix use-after-free on cached last_lookup partition Date: Thu, 7 May 2020 16:52:36 +0800 Message-Id: <20200507085239.1354854-2-ming.lei@redhat.com> In-Reply-To: <20200507085239.1354854-1-ming.lei@redhat.com> References: <20200507085239.1354854-1-ming.lei@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Content-Transfer-Encoding: quoted-printable Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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 hd_struct_free() is called, then use-after-free is trigge= red 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 hd_struct_free() which is the release handle of the partition's percpu-refcount, so that n= o IO path can overwrite .last_lookup after it is cleared in hd_struct_free(= ). 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/partitions/core.c | 12 +++++++++++- include/linux/genhd.h | 1 + 4 files changed, 17 insertions(+), 14 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index ec50d7e6be21..826a8980997d 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1363,18 +1363,6 @@ void blk_account_io_start(struct request *rq, bool= new_io) part_stat_inc(part, merges[rw]); } else { part =3D 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 =3D &rq->rq_disk->part0; - hd_struct_get(part); - } part_inc_in_flight(rq->q, part, rw); rq->part =3D part; } diff --git a/block/genhd.c b/block/genhd.c index c05d509877fa..8b33f0e54356 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -359,17 +359,21 @@ struct hd_struct *disk_map_sector_rcu(struct gendis= k *disk, sector_t sector) ptbl =3D rcu_dereference(disk->part_tbl); =20 part =3D 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; =20 for (i =3D 1; i < ptbl->len; i++) { part =3D rcu_dereference(ptbl->part[i]); =20 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; } =20 diff --git a/block/partitions/core.c b/block/partitions/core.c index c085bf85509b..b6cbc9b98426 100644 --- a/block/partitions/core.c +++ b/block/partitions/core.c @@ -288,6 +288,11 @@ static void hd_struct_free_work(struct work_struct *= work) static void hd_struct_free(struct percpu_ref *ref) { struct hd_struct *part =3D container_of(ref, struct hd_struct, ref); + struct disk_part_tbl *ptbl =3D + rcu_dereference_protected(part->disk->part_tbl, 1); + + rcu_assign_pointer(ptbl->last_lookup, NULL); + put_device(disk_to_dev(part->disk)); =20 INIT_RCU_WORK(&part->rcu_work, hd_struct_free_work); queue_rcu_work(system_wq, &part->rcu_work); @@ -309,8 +314,12 @@ void delete_partition(struct gendisk *disk, struct h= d_struct *part) struct disk_part_tbl *ptbl =3D rcu_dereference_protected(disk->part_tbl, 1); =20 + /* + * make sure disk won't be gone because ->part_tbl is referenced in + * this part's release handler + */ + get_device(disk_to_dev(disk)); rcu_assign_pointer(ptbl->part[part->partno], NULL); - rcu_assign_pointer(ptbl->last_lookup, NULL); kobject_put(part->holder_dir); device_del(part_to_dev(part)); =20 @@ -393,6 +402,7 @@ static struct hd_struct *add_partition(struct gendisk= *disk, int partno, p->nr_sects =3D len; p->partno =3D partno; p->policy =3D get_disk_ro(disk); + p->disk =3D disk; =20 if (info) { struct partition_meta_info *pinfo; diff --git a/include/linux/genhd.h b/include/linux/genhd.h index f9c226f9546a..c28d1d9bfa72 100644 --- a/include/linux/genhd.h +++ b/include/linux/genhd.h @@ -85,6 +85,7 @@ struct hd_struct { struct disk_stats dkstats; #endif struct percpu_ref ref; + struct gendisk *disk; struct rcu_work rcu_work; }; =20 --=20 2.25.2