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=-11.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 3835AC433B4 for ; Tue, 4 May 2021 11:44:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E7B9261185 for ; Tue, 4 May 2021 11:44:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230136AbhEDLpG (ORCPT ); Tue, 4 May 2021 07:45:06 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:54062 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230046AbhEDLpF (ORCPT ); Tue, 4 May 2021 07:45:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620128649; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=QU9ihjLOet5kIKVF+koaJjcljy5cIb20fT3nMkZe3gw=; b=b6cxF1HKTKEeUM2YprsLscsXiVZXDA2Eh+3ddR/UpsKgOUIGVwLKa3nt6BwyqmxrmPbSFE 3Ua/9BYJ1F3gf38L/kRFjRWDBaUtdTt/NNJsvXnALCrKGnqHiA40QAoLAeTtsJ6fQvBvDT cEUuDIee8cjFCAyjVkRNxNYsczzhWg0= 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-447-Fh6b55hFNVmNTccbl0cLWg-1; Tue, 04 May 2021 07:44:05 -0400 X-MC-Unique: Fh6b55hFNVmNTccbl0cLWg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 60F5F8030D5; Tue, 4 May 2021 11:44:03 +0000 (UTC) Received: from T590 (ovpn-12-36.pek2.redhat.com [10.72.12.36]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6EBD65C1B4; Tue, 4 May 2021 11:43:55 +0000 (UTC) Date: Tue, 4 May 2021 19:43:51 +0800 From: Ming Lei To: John Garry Cc: Jens Axboe , linux-block@vger.kernel.org, Bart Van Assche , Khazhy Kumykov , Shin'ichiro Kawasaki , Hannes Reinecke , David Jeffery Subject: Re: [PATCH V4 0/4] blk-mq: fix request UAF related with iterating over tagset requests Message-ID: References: <20210429023458.3044317-1-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue, May 04, 2021 at 11:15:37AM +0100, John Garry wrote: > On 29/04/2021 03:34, Ming Lei wrote: > > Hi Jens, > > > > This patchset fixes the request UAF issue by one simple approach, > > without clearing ->rqs[] in fast path. > > > > 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. > > > > I had a go at testing this. Without any modifications for testing, it looks > ok. > > However I also tested by adding an artificial delay in bt_iter() - otherwise > it may not be realistic to trigger some UAF issues in sane timeframes. > > So I made this change: > > --- a/block/blk-mq-tag.c > +++ b/block/blk-mq-tag.c > @@ -215,8 +215,11 @@ static bool bt_iter(struct sbitmap *bitmap, unsigned > int bitnr, void *data) > * We can hit rq == NULL here, because the tagging functions > * test and set the bit before assigning ->rqs[]. > */ > - if (rq && rq->q == hctx->queue && rq->mq_hctx == hctx) > - return iter_data->fn(hctx, rq, iter_data->data, reserved); > + if (rq) { > + mdelay(50); > + if (rq->q == hctx->queue && rq->mq_hctx == hctx) > + return iter_data->fn(hctx, rq, iter_data->data, reserved); > + } > return true; > } hammmm, forget to cover bt_iter(), please test the following delta patch: diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index a3be267212b9..27815114ee3f 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -206,18 +206,28 @@ static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) struct blk_mq_tags *tags = hctx->tags; bool reserved = iter_data->reserved; struct request *rq; + unsigned long flags; + bool ret = true; if (!reserved) bitnr += tags->nr_reserved_tags; - rq = tags->rqs[bitnr]; + spin_lock_irqsave(&tags->lock, flags); + rq = tags->rqs[bitnr]; /* * We can hit rq == NULL here, because the tagging functions * test and set the bit before assigning ->rqs[]. */ - if (rq && rq->q == hctx->queue && rq->mq_hctx == hctx) - return iter_data->fn(hctx, rq, iter_data->data, reserved); - return true; + if (!rq || !refcount_inc_not_zero(&rq->ref)) { + spin_unlock_irqrestore(&tags->lock, flags); + return true; + } + spin_unlock_irqrestore(&tags->lock, flags); + + if (rq->q == hctx->queue && rq->mq_hctx == hctx) + ret = iter_data->fn(hctx, rq, iter_data->data, reserved); + blk_mq_put_rq_ref(rq); + return ret; } /** Thanks, Ming