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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5CC3DC43219 for ; Mon, 7 Mar 2022 19:33:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245115AbiCGTea (ORCPT ); Mon, 7 Mar 2022 14:34:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51928 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231339AbiCGTe3 (ORCPT ); Mon, 7 Mar 2022 14:34:29 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 91AC13DA51; Mon, 7 Mar 2022 11:33:33 -0800 (PST) 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 ams.source.kernel.org (Postfix) with ESMTPS id 29C48B81675; Mon, 7 Mar 2022 19:33:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 694ECC340E9; Mon, 7 Mar 2022 19:33:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1646681610; bh=r6rpRPmNION6kq25dM57jcD1aBaQlpYB8q4rQChmGQs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bSGRf/9tVP9v5y85akWLJwNB97//Y4r1iv+lu4vG3xZWFdEF1JRcM3ZqyoZORCqtZ WQWdlmrMpl6pPnK+DOyjqKlbccp63wNpKmRdgsSRNmN/BxBoqDdt17zdu1HXqAqyQ/ huUKcW5PY9qg1w3M1omXyiGaa+Y8mFLWkoOtW6Lo= Date: Mon, 7 Mar 2022 20:33:27 +0100 From: Greg KH To: Lee Jones Cc: mst@redhat.com, jasowang@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, stable@vger.kernel.org, syzbot+adc3cb32385586bec859@syzkaller.appspotmail.com Subject: Re: [PATCH 1/1] vhost: Protect the virtqueue from being cleared whilst still in use Message-ID: References: <20220307191757.3177139-1-lee.jones@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220307191757.3177139-1-lee.jones@linaro.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 07, 2022 at 07:17:57PM +0000, Lee Jones wrote: > vhost_vsock_handle_tx_kick() already holds the mutex during its call > to vhost_get_vq_desc(). All we have to do here is take the same lock > during virtqueue clean-up and we mitigate the reported issues. > > Also WARN() as a precautionary measure. The purpose of this is to > capture possible future race conditions which may pop up over time. > > Link: https://syzkaller.appspot.com/bug?extid=279432d30d825e63ba00 > > Cc: > Reported-by: syzbot+adc3cb32385586bec859@syzkaller.appspotmail.com > Signed-off-by: Lee Jones > --- > drivers/vhost/vhost.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 59edb5a1ffe28..ef7e371e3e649 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -693,6 +693,15 @@ void vhost_dev_cleanup(struct vhost_dev *dev) > int i; > > for (i = 0; i < dev->nvqs; ++i) { > + /* No workers should run here by design. However, races have > + * previously occurred where drivers have been unable to flush > + * all work properly prior to clean-up. Without a successful > + * flush the guest will malfunction, but avoiding host memory > + * corruption in those cases does seem preferable. > + */ > + WARN_ON(mutex_is_locked(&dev->vqs[i]->mutex)); So you are trading one syzbot triggered issue for another one in the future? :) If this ever can happen, handle it, but don't log it with a WARN_ON() as that will trigger the panic-on-warn boxes, as well as syzbot. Unless you want that to happen? And what happens if the mutex is locked _RIGHT_ after you checked it? You still have a race... thanks, greg k-h 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 Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id EC43FC43217 for ; Mon, 7 Mar 2022 19:33:39 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 9DD9C80C2A; Mon, 7 Mar 2022 19:33:39 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id vi99ug1_OnMb; Mon, 7 Mar 2022 19:33:38 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp1.osuosl.org (Postfix) with ESMTPS id 31B9280C24; Mon, 7 Mar 2022 19:33:38 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 14F6DC001D; Mon, 7 Mar 2022 19:33:38 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [IPv6:2605:bc80:3010::137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 2C587C000B for ; Mon, 7 Mar 2022 19:33:36 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 1572340278 for ; Mon, 7 Mar 2022 19:33:36 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Authentication-Results: smtp4.osuosl.org (amavisd-new); dkim=pass (1024-bit key) header.d=linuxfoundation.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id tV7cLmo0oywJ for ; Mon, 7 Mar 2022 19:33:35 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.8.0 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by smtp4.osuosl.org (Postfix) with ESMTPS id 2E1F44025E for ; Mon, 7 Mar 2022 19:33:35 +0000 (UTC) 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 ams.source.kernel.org (Postfix) with ESMTPS id 3CCA7B81698; Mon, 7 Mar 2022 19:33:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 694ECC340E9; Mon, 7 Mar 2022 19:33:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1646681610; bh=r6rpRPmNION6kq25dM57jcD1aBaQlpYB8q4rQChmGQs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bSGRf/9tVP9v5y85akWLJwNB97//Y4r1iv+lu4vG3xZWFdEF1JRcM3ZqyoZORCqtZ WQWdlmrMpl6pPnK+DOyjqKlbccp63wNpKmRdgsSRNmN/BxBoqDdt17zdu1HXqAqyQ/ huUKcW5PY9qg1w3M1omXyiGaa+Y8mFLWkoOtW6Lo= Date: Mon, 7 Mar 2022 20:33:27 +0100 From: Greg KH To: Lee Jones Subject: Re: [PATCH 1/1] vhost: Protect the virtqueue from being cleared whilst still in use Message-ID: References: <20220307191757.3177139-1-lee.jones@linaro.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220307191757.3177139-1-lee.jones@linaro.org> Cc: syzbot+adc3cb32385586bec859@syzkaller.appspotmail.com, kvm@vger.kernel.org, mst@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, virtualization@lists.linux-foundation.org X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Mon, Mar 07, 2022 at 07:17:57PM +0000, Lee Jones wrote: > vhost_vsock_handle_tx_kick() already holds the mutex during its call > to vhost_get_vq_desc(). All we have to do here is take the same lock > during virtqueue clean-up and we mitigate the reported issues. > > Also WARN() as a precautionary measure. The purpose of this is to > capture possible future race conditions which may pop up over time. > > Link: https://syzkaller.appspot.com/bug?extid=279432d30d825e63ba00 > > Cc: > Reported-by: syzbot+adc3cb32385586bec859@syzkaller.appspotmail.com > Signed-off-by: Lee Jones > --- > drivers/vhost/vhost.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 59edb5a1ffe28..ef7e371e3e649 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -693,6 +693,15 @@ void vhost_dev_cleanup(struct vhost_dev *dev) > int i; > > for (i = 0; i < dev->nvqs; ++i) { > + /* No workers should run here by design. However, races have > + * previously occurred where drivers have been unable to flush > + * all work properly prior to clean-up. Without a successful > + * flush the guest will malfunction, but avoiding host memory > + * corruption in those cases does seem preferable. > + */ > + WARN_ON(mutex_is_locked(&dev->vqs[i]->mutex)); So you are trading one syzbot triggered issue for another one in the future? :) If this ever can happen, handle it, but don't log it with a WARN_ON() as that will trigger the panic-on-warn boxes, as well as syzbot. Unless you want that to happen? And what happens if the mutex is locked _RIGHT_ after you checked it? You still have a race... thanks, greg k-h _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization