From patchwork Mon Dec 27 15:30:43 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 528671 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4CC7C433EF for ; Mon, 27 Dec 2021 15:32:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237575AbhL0Pc5 (ORCPT ); Mon, 27 Dec 2021 10:32:57 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:33992 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238049AbhL0Pct (ORCPT ); Mon, 27 Dec 2021 10:32:49 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E0A4E610A6; Mon, 27 Dec 2021 15:32:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C26F3C36AEB; Mon, 27 Dec 2021 15:32:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1640619168; bh=4bRulaxE7kkQ/lwnl9f1sNtyQRvG9h/NNXObngGG0BA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nFV5yxeD+TkAQ+0MCNM5qhBWtLPTAmUeqyHexHrQJ699frJtvHPmMUHHt5CundE0Y s+Y6ACEIfxwH4Wfq2avkbMvLRgEArYWbk+l55mE/QRbVOAlNRWX5HN3AeJ+e/IAmRM 1kFChayljlIbouOJAOeGOLWCy1EMc53+BfeC9N20= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dmitrii Tcvetkov , Douglas Anderson , Paolo Valente , Jens Axboe , Yu Kuai Subject: [PATCH 4.19 06/38] block, bfq: fix use after free in bfq_bfqq_expire Date: Mon, 27 Dec 2021 16:30:43 +0100 Message-Id: <20211227151319.590190184@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211227151319.379265346@linuxfoundation.org> References: <20211227151319.379265346@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Paolo Valente commit eed47d19d9362bdd958e4ab56af480b9dbf6b2b6 upstream. The function bfq_bfqq_expire() invokes the function __bfq_bfqq_expire(), and the latter may free the in-service bfq-queue. If this happens, then no other instruction of bfq_bfqq_expire() must be executed, or a use-after-free will occur. Basing on the assumption that __bfq_bfqq_expire() invokes bfq_put_queue() on the in-service bfq-queue exactly once, the queue is assumed to be freed if its refcounter is equal to one right before invoking __bfq_bfqq_expire(). But, since commit 9dee8b3b057e ("block, bfq: fix queue removal from weights tree") this assumption is false. __bfq_bfqq_expire() may also invoke bfq_weights_tree_remove() and, since commit 9dee8b3b057e ("block, bfq: fix queue removal from weights tree"), also the latter function may invoke bfq_put_queue(). So __bfq_bfqq_expire() may invoke bfq_put_queue() twice, and this is the actual case where the in-service queue may happen to be freed. To address this issue, this commit moves the check on the refcounter of the queue right around the last bfq_put_queue() that may be invoked on the queue. Fixes: 9dee8b3b057e ("block, bfq: fix queue removal from weights tree") Reported-by: Dmitrii Tcvetkov Reported-by: Douglas Anderson Tested-by: Dmitrii Tcvetkov Tested-by: Douglas Anderson Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe Signed-off-by: Yu Kuai Signed-off-by: Greg Kroah-Hartman --- block/bfq-iosched.c | 15 +++++++-------- block/bfq-iosched.h | 2 +- block/bfq-wf2q.c | 17 +++++++++++++++-- 3 files changed, 23 insertions(+), 11 deletions(-) --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2816,7 +2816,7 @@ static void bfq_dispatch_remove(struct r bfq_remove_request(q, rq); } -static void __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq) +static bool __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq) { /* * If this bfqq is shared between multiple processes, check @@ -2849,9 +2849,11 @@ static void __bfq_bfqq_expire(struct bfq /* * All in-service entities must have been properly deactivated * or requeued before executing the next function, which - * resets all in-service entites as no more in service. + * resets all in-service entities as no more in service. This + * may cause bfqq to be freed. If this happens, the next + * function returns true. */ - __bfq_bfqd_reset_in_service(bfqd); + return __bfq_bfqd_reset_in_service(bfqd); } /** @@ -3256,7 +3258,6 @@ void bfq_bfqq_expire(struct bfq_data *bf bool slow; unsigned long delta = 0; struct bfq_entity *entity = &bfqq->entity; - int ref; /* * Check whether the process is slow (see bfq_bfqq_is_slow). @@ -3325,10 +3326,8 @@ void bfq_bfqq_expire(struct bfq_data *bf * reason. */ __bfq_bfqq_recalc_budget(bfqd, bfqq, reason); - ref = bfqq->ref; - __bfq_bfqq_expire(bfqd, bfqq); - - if (ref == 1) /* bfqq is gone, no more actions on it */ + if (__bfq_bfqq_expire(bfqd, bfqq)) + /* bfqq is gone, no more actions on it */ return; bfqq->injected_service = 0; --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -993,7 +993,7 @@ bool __bfq_deactivate_entity(struct bfq_ bool ins_into_idle_tree); bool next_queue_may_preempt(struct bfq_data *bfqd); struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd); -void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd); +bool __bfq_bfqd_reset_in_service(struct bfq_data *bfqd); void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, bool ins_into_idle_tree, bool expiration); void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq); --- a/block/bfq-wf2q.c +++ b/block/bfq-wf2q.c @@ -1600,7 +1600,8 @@ struct bfq_queue *bfq_get_next_queue(str return bfqq; } -void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd) +/* returns true if the in-service queue gets freed */ +bool __bfq_bfqd_reset_in_service(struct bfq_data *bfqd) { struct bfq_queue *in_serv_bfqq = bfqd->in_service_queue; struct bfq_entity *in_serv_entity = &in_serv_bfqq->entity; @@ -1624,8 +1625,20 @@ void __bfq_bfqd_reset_in_service(struct * service tree either, then release the service reference to * the queue it represents (taken with bfq_get_entity). */ - if (!in_serv_entity->on_st) + if (!in_serv_entity->on_st) { + /* + * If no process is referencing in_serv_bfqq any + * longer, then the service reference may be the only + * reference to the queue. If this is the case, then + * bfqq gets freed here. + */ + int ref = in_serv_bfqq->ref; bfq_put_queue(in_serv_bfqq); + if (ref == 1) + return true; + } + + return false; } void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,