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=-16.0 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 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 1D5A0C433B4 for ; Tue, 27 Apr 2021 15:11:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CFD15613DD for ; Tue, 27 Apr 2021 15:11:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236512AbhD0PL5 (ORCPT ); Tue, 27 Apr 2021 11:11:57 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:40056 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235466AbhD0PL4 (ORCPT ); Tue, 27 Apr 2021 11:11:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619536273; 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=VDh9wS3jss8fWGInb7YcjAdKBf4lUubnuKTnTwvKyL4=; b=hW6NPw/VW0GFuOjjZx/qD1mEItgdy3PdzZf/gTVSBGqe4ma5TAHfiJ2sJzAksxS7iRTnH1 b8tqY9YKD64Gx61XFA+V7c762pBB/hrE8IC92XzZqy/bToEFc3JGd7IY888PyasQ2EXnko mxmyIQ77UZqB458gzKAG2MzHDW/mYXI= 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-200-PC1HauYMNYCsJ_QGuOoXnQ-1; Tue, 27 Apr 2021 11:11:09 -0400 X-MC-Unique: PC1HauYMNYCsJ_QGuOoXnQ-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 D51DE1922963; Tue, 27 Apr 2021 15:11:07 +0000 (UTC) Received: from localhost (ovpn-12-67.pek2.redhat.com [10.72.12.67]) by smtp.corp.redhat.com (Postfix) with ESMTP id 04FC95C3F8; Tue, 27 Apr 2021 15:11:06 +0000 (UTC) From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, Bart Van Assche , Khazhy Kumykov , Shin'ichiro Kawasaki , Hannes Reinecke , John Garry , David Jeffery , Ming Lei Subject: [PATCH V3 2/3] blk-mq: grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter Date: Tue, 27 Apr 2021 23:10:57 +0800 Message-Id: <20210427151058.2833168-3-ming.lei@redhat.com> In-Reply-To: <20210427151058.2833168-1-ming.lei@redhat.com> References: <20210427151058.2833168-1-ming.lei@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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 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. Signed-off-by: Ming Lei --- block/blk-mq-tag.c | 22 ++++++++++++++++------ block/blk-mq.c | 14 +++++++++----- block/blk-mq.h | 1 + 3 files changed, 26 insertions(+), 11 deletions(-) diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 2a37731e8244..9329b94a9743 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -264,6 +264,8 @@ 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; + bool iter_static_rqs = !!(iter_data->flags & BT_TAG_ITER_STATIC_RQS); if (!reserved) bitnr += tags->nr_reserved_tags; @@ -272,16 +274,21 @@ 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 + else { rq = tags->rqs[bitnr]; - if (!rq) - return true; + if (!rq || !refcount_inc_not_zero(&rq->ref)) + 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); + ret = true; + else + ret = iter_data->fn(rq, iter_data->data, reserved); + if (!iter_static_rqs) + blk_mq_put_rq_ref(rq); + return ret; } /** @@ -348,6 +355,9 @@ 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 927189a55575..4bd6c11bd8bc 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 3616453ca28c..143afe42c63a 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