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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 5D7E9C43462 for ; Tue, 11 May 2021 15:23:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3C022615FF for ; Tue, 11 May 2021 15:23:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231704AbhEKPYP (ORCPT ); Tue, 11 May 2021 11:24:15 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:58094 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231761AbhEKPYJ (ORCPT ); Tue, 11 May 2021 11:24:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620746580; 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=MNNlD8pdvxedbDEcxxhaYjuIJfJH0jY7V5CgESOzPOw=; b=VC0NmHbtRnNQ2SjYB4aG9U/U19NF4JrXZIgyWKHrgIitN1m8lAClv9ostjBoPTXdoHGYYN du5zPv1qXj/kaE1lJF5sdkpC+okJe8Or4ipn3k6Zm17Nu8fY482Gx4vz06f3hr5pW8xN+3 id5jpzZoWWbCbtwU/Zo2MyiMqks1SDI= 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-455-JPhfrFt3MlaMPyNZ1COM6Q-1; Tue, 11 May 2021 11:22:58 -0400 X-MC-Unique: JPhfrFt3MlaMPyNZ1COM6Q-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2C809106BAA6; Tue, 11 May 2021 15:22:57 +0000 (UTC) Received: from localhost (ovpn-12-205.pek2.redhat.com [10.72.12.205]) by smtp.corp.redhat.com (Postfix) with ESMTP id A5A6E5D6D1; Tue, 11 May 2021 15:22:52 +0000 (UTC) From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, Bart Van Assche , Hannes Reinecke , John Garry , Christoph Hellwig , David Jeffery , Shinichiro Kawasaki , Ming Lei Subject: [PATCH V7 2/4] blk-mq: grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter Date: Tue, 11 May 2021 23:22:34 +0800 Message-Id: <20210511152236.763464-3-ming.lei@redhat.com> In-Reply-To: <20210511152236.763464-1-ming.lei@redhat.com> References: <20210511152236.763464-1-ming.lei@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter(), and this way will prevent the request from being re-used when ->fn is running. The approach is same as what we do during handling timeout. Fix request use-after-free(UAF) related with completion race or queue releasing: - If one rq is referred before rq->q is frozen, then queue won't be frozen before the request is released during iteration. - If one rq is referred after rq->q is frozen, refcount_inc_not_zero() will return false, and we won't iterate over this request. However, still one request UAF not covered: refcount_inc_not_zero() may read one freed request, and it will be handled in next patch. Tested-by: John Garry Reviewed-by: Christoph Hellwig Reviewed-by: Bart Van Assche Signed-off-by: Ming Lei --- block/blk-mq-tag.c | 44 +++++++++++++++++++++++++++++++++----------- block/blk-mq.c | 14 +++++++++----- block/blk-mq.h | 1 + 3 files changed, 43 insertions(+), 16 deletions(-) diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 2a37731e8244..544edf2c56a5 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -199,6 +199,16 @@ struct bt_iter_data { bool reserved; }; +static struct request *blk_mq_find_and_get_req(struct blk_mq_tags *tags, + unsigned int bitnr) +{ + struct request *rq = tags->rqs[bitnr]; + + if (!rq || !refcount_inc_not_zero(&rq->ref)) + return NULL; + return rq; +} + static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) { struct bt_iter_data *iter_data = data; @@ -206,18 +216,22 @@ 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; + bool ret = true; if (!reserved) bitnr += tags->nr_reserved_tags; - 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; + rq = blk_mq_find_and_get_req(tags, bitnr); + if (!rq) + return true; + + 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; } /** @@ -264,6 +278,8 @@ static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) struct blk_mq_tags *tags = iter_data->tags; bool reserved = iter_data->flags & BT_TAG_ITER_RESERVED; struct request *rq; + bool ret = true; + bool iter_static_rqs = !!(iter_data->flags & BT_TAG_ITER_STATIC_RQS); if (!reserved) bitnr += tags->nr_reserved_tags; @@ -272,16 +288,19 @@ static bool bt_tags_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 (iter_data->flags & BT_TAG_ITER_STATIC_RQS) + if (iter_static_rqs) rq = tags->static_rqs[bitnr]; else - rq = tags->rqs[bitnr]; + rq = blk_mq_find_and_get_req(tags, bitnr); if (!rq) return true; - if ((iter_data->flags & BT_TAG_ITER_STARTED) && - !blk_mq_request_started(rq)) - return true; - return iter_data->fn(rq, iter_data->data, reserved); + + if (!(iter_data->flags & BT_TAG_ITER_STARTED) || + blk_mq_request_started(rq)) + ret = iter_data->fn(rq, iter_data->data, reserved); + if (!iter_static_rqs) + blk_mq_put_rq_ref(rq); + return ret; } /** @@ -348,6 +367,9 @@ void blk_mq_all_tag_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn, * indicates whether or not @rq is a reserved request. Return * true to continue iterating tags, false to stop. * @priv: Will be passed as second argument to @fn. + * + * We grab one request reference before calling @fn and release it after + * @fn returns. */ void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, busy_tag_iter_fn *fn, void *priv) diff --git a/block/blk-mq.c b/block/blk-mq.c index 466676bc2f0b..d053e80fa6d7 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -909,6 +909,14 @@ static bool blk_mq_req_expired(struct request *rq, unsigned long *next) return false; } +void blk_mq_put_rq_ref(struct request *rq) +{ + if (is_flush_rq(rq, rq->mq_hctx)) + rq->end_io(rq, 0); + else if (refcount_dec_and_test(&rq->ref)) + __blk_mq_free_request(rq); +} + static bool blk_mq_check_expired(struct blk_mq_hw_ctx *hctx, struct request *rq, void *priv, bool reserved) { @@ -942,11 +950,7 @@ static bool blk_mq_check_expired(struct blk_mq_hw_ctx *hctx, if (blk_mq_req_expired(rq, next)) blk_mq_rq_timed_out(rq, reserved); - if (is_flush_rq(rq, hctx)) - rq->end_io(rq, 0); - else if (refcount_dec_and_test(&rq->ref)) - __blk_mq_free_request(rq); - + blk_mq_put_rq_ref(rq); return true; } diff --git a/block/blk-mq.h b/block/blk-mq.h index 9ce64bc4a6c8..556368d2c5b6 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -47,6 +47,7 @@ void blk_mq_add_to_requeue_list(struct request *rq, bool at_head, void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list); struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *start); +void blk_mq_put_rq_ref(struct request *rq); /* * Internal helpers for allocating/freeing the request map -- 2.29.2