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=-12.9 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,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 48C5BC4338F for ; Fri, 6 Aug 2021 07:50:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 28F0E60F25 for ; Fri, 6 Aug 2021 07:50:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243255AbhHFHu4 (ORCPT ); Fri, 6 Aug 2021 03:50:56 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:8372 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243643AbhHFHuv (ORCPT ); Fri, 6 Aug 2021 03:50:51 -0400 Received: from dggemv711-chm.china.huawei.com (unknown [172.30.72.57]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4GgyGm6y92z84DY; Fri, 6 Aug 2021 15:46:40 +0800 (CST) Received: from dggema762-chm.china.huawei.com (10.1.198.204) by dggemv711-chm.china.huawei.com (10.1.198.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Fri, 6 Aug 2021 15:50:32 +0800 Received: from [10.174.176.73] (10.174.176.73) by dggema762-chm.china.huawei.com (10.1.198.204) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Fri, 6 Aug 2021 15:50:32 +0800 Subject: Re: [PATCH V7 0/4] blk-mq: fix request UAF related with iterating over tagset requests To: Ming Lei CC: Jens Axboe , , "Bart Van Assche" , Hannes Reinecke , John Garry , Christoph Hellwig , David Jeffery , Shinichiro Kawasaki References: <20210511152236.763464-1-ming.lei@redhat.com> <678fd2c5-587d-6abe-4348-067210d4adae@huawei.com> From: "yukuai (C)" Message-ID: <3809c299-4f40-3614-c233-184d8a39e286@huawei.com> Date: Fri, 6 Aug 2021 15:50:31 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="gbk"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.176.73] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggema762-chm.china.huawei.com (10.1.198.204) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2021/08/06 12:12, Ming Lei wrote: > On Fri, Aug 06, 2021 at 11:40:25AM +0800, yukuai (C) wrote: >> On 2021/05/11 23:22, Ming Lei wrote: >>> Hi Jens, >>> >>> This patchset fixes the request UAF issue by one simple approach, >>> without clearing ->rqs[] in fast path, please consider it for 5.13. >>> >>> 1) grab request's ref before calling ->fn in blk_mq_tagset_busy_iter, >>> and release it after calling ->fn, so ->fn won't be called for one >>> request if its queue is frozen, done in 2st patch >>> >>> 2) clearing any stale request referred in ->rqs[] before freeing the >>> request pool, one per-tags spinlock is added for protecting >>> grabbing request ref vs. clearing ->rqs[tag], so UAF by refcount_inc_not_zero >>> in bt_tags_iter() is avoided, done in 3rd patch. >>> >>> V7: >>> - fix one null-ptr-deref during updating nr_hw_queues, because >>> blk_mq_clear_flush_rq_mapping() may touch non-mapped hw queue's >>> tags, only patch 4/4 is modified, reported and verified by >>> Shinichiro Kawasaki >>> - run blktests and not see regression >>> >>> V6: >>> - hold spin lock when reading rq via ->rq[tag_bit], the issue is >>> added in V5 >>> - make blk_mq_find_and_get_req() more clean, as suggested by Bart >>> - not hold tags->lock when clearing ->rqs[] for avoiding to disable >>> interrupt a bit long, as suggested by Bart >>> - code style change, as suggested by Christoph >>> >>> V5: >>> - cover bt_iter() by same approach taken in bt_tags_iter(), and pass >>> John's invasive test >>> - add tested-by/reviewed-by tag >>> >>> V4: >>> - remove hctx->fq-flush_rq from tags->rqs[] before freeing hw queue, >>> patch 4/4 is added, which is based on David's patch. >>> >>> V3: >>> - drop patches for completing requests started in iterator ->fn, >>> because blk-mq guarantees that valid request is passed to ->fn, >>> and it is driver's responsibility for avoiding double completion. >>> And drivers works well for not completing rq twice. >>> - add one patch for avoiding double accounting of flush rq >>> >>> V2: >>> - take Bart's suggestion to not add blk-mq helper for completing >>> requests when it is being iterated >>> - don't grab rq->ref if the iterator is over static rqs because >>> the use case do require to iterate over all requests no matter if >>> the request is initialized or not >>> >>> >>> Ming Lei (4): >>> block: avoid double io accounting for flush request >>> blk-mq: grab rq->refcount before calling ->fn in >>> blk_mq_tagset_busy_iter >>> blk-mq: clear stale request in tags->rq[] before freeing one request >>> pool >>> blk-mq: clearing flush request reference in tags->rqs[] >>> >>> block/blk-flush.c | 3 +- >>> block/blk-mq-tag.c | 49 ++++++++++++++++++------ >>> block/blk-mq-tag.h | 6 +++ >>> block/blk-mq.c | 95 ++++++++++++++++++++++++++++++++++++++++------ >>> block/blk-mq.h | 1 + >>> 5 files changed, 130 insertions(+), 24 deletions(-) >>> >> >> Hi, ming >> >> I see this patchset was applied to fix the problem while iterating over >> tagset, however blk_mq_tag_to_rq() is still untouched, and this >> interface might still return freed request. >> >> Any reason why this interface didn't use the same solution ? >> (hold tags->lock and return null if ref is 0) > > It is driver's responsibility to cover race between normal completion > and timeout/error handing, so driver has the knowledge if one tag is valid > or not. In short, it is driver's responsibility to guarantee that valid 'tag' > is passed to blk_mq_tag_to_rq(). > Thanks for the explanation. Best regards, Kuai