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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 A323BC433DF for ; Mon, 8 Jun 2020 01:54:20 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7C9072063A for ; Mon, 8 Jun 2020 01:54:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7C9072063A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id 1B4E385618; Mon, 8 Jun 2020 01:54:20 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 6bSZOh7U12Gf; Mon, 8 Jun 2020 01:54:18 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by fraxinus.osuosl.org (Postfix) with ESMTP id 5F4A6854CC; Mon, 8 Jun 2020 01:54:18 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 4B1EFC07FF; Mon, 8 Jun 2020 01:54:18 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id CF63CC016F for ; Mon, 8 Jun 2020 01:54:16 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id BB21620005 for ; Mon, 8 Jun 2020 01:54:16 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id KyVKR+JVdTKM for ; Mon, 8 Jun 2020 01:54:15 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by silver.osuosl.org (Postfix) with ESMTPS id BDD161FE0A for ; Mon, 8 Jun 2020 01:54:15 +0000 (UTC) IronPort-SDR: 0FjgxXm0tWKarBxC8rAoRS17C8EtuKKcLNiIBfi3/HSce5OBp415dUYW+GThIjnTlaDXKV4zHx dyo8Yc9/4v2A== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Jun 2020 18:54:15 -0700 IronPort-SDR: kIeNvx4NqtmcJGiRPkJIqcTlzYKbxEFbr3Kc3yvDdp8bwHeYxxv/rQH0fV2w+2O4RdlVqQkr9+ km9955wTRgcQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,486,1583222400"; d="scan'208";a="295297387" Received: from allen-box.sh.intel.com (HELO [10.239.159.139]) ([10.239.159.139]) by fmsmga004.fm.intel.com with ESMTP; 07 Jun 2020 18:54:12 -0700 Subject: Re: [PATCH V4 2/3] iommu: Take lock before reading iommu group default domain type To: Sai Praneeth Prakhya , iommu@lists.linux-foundation.org References: <379b0d7307bb76699e2438a21f6c8259a7538ef7.1591290586.git.sai.praneeth.prakhya@intel.com> From: Lu Baolu Message-ID: <106b9809-0cb1-77c7-61c0-c870ed6abf16@linux.intel.com> Date: Mon, 8 Jun 2020 09:50:17 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <379b0d7307bb76699e2438a21f6c8259a7538ef7.1591290586.git.sai.praneeth.prakhya@intel.com> Content-Language: en-US Cc: Ashok Raj , Will Deacon , Robin Murphy , Christoph Hellwig X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 6/5/20 9:32 AM, Sai Praneeth Prakhya wrote: > "/sys/kernel/iommu_groups//type" file could be read to find out the > default domain type of an iommu group. The default domain of an iommu group > doesn't change after booting and hence could be read directly. But, > after addding support to dynamically change iommu group default domain, the > above assumption no longer stays valid. > > iommu group default domain type could be changed at any time by writing to > "/sys/kernel/iommu_groups//type". So, take group mutex before > reading iommu group default domain type so that the user wouldn't see stale > values or iommu_group_show_type() doesn't try to derefernce stale pointers. > > Cc: Christoph Hellwig > Cc: Joerg Roedel > Cc: Ashok Raj > Cc: Will Deacon > Cc: Lu Baolu Reviewed-by: Lu Baolu Best regards, baolu > Cc: Sohil Mehta > Cc: Robin Murphy > Cc: Jacob Pan > Signed-off-by: Sai Praneeth Prakhya > --- > drivers/iommu/iommu.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index b023f06f12d6..eb133ee5c13a 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -501,6 +501,7 @@ static ssize_t iommu_group_show_type(struct iommu_group *group, > { > char *type = "unknown\n"; > > + mutex_lock(&group->mutex); > if (group->default_domain) { > switch (group->default_domain->type) { > case IOMMU_DOMAIN_BLOCKED: > @@ -517,6 +518,7 @@ static ssize_t iommu_group_show_type(struct iommu_group *group, > break; > } > } > + mutex_unlock(&group->mutex); > strcpy(buf, type); > > return strlen(type); > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu