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 80472C6FD18 for ; Tue, 28 Mar 2023 15:45:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233527AbjC1Pp3 (ORCPT ); Tue, 28 Mar 2023 11:45:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59072 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233524AbjC1PpK (ORCPT ); Tue, 28 Mar 2023 11:45:10 -0400 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D41BBEB46; Tue, 28 Mar 2023 08:44:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1680018292; x=1711554292; h=date:from:to:cc:subject:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=4pyh949E97gRjYQQaTn6XtjnpRmrAxMmEo978KIuT4s=; b=fbvIfUM7l8Z2BLXiD1GhoPWjWLHv2iNWOi/ypz5fv4Ue+sk1k8OduYqY YSJe6pn404OtSCNQ+5y7auuex10CvaRZizixptqYnSxcDOFHb3Rq5x/MI rLxj7cBeDh8AGLWzNeaFmbON7zAoZe1uWfQnSKLw6qwniyQdNUnOd/JiI J7jlcourEnkKBSZnLVcmm8nJlJxNbFgGd1HEWYqNs9rZ2Z4heoLD1NbDL jIPK9WeaVGugD+Vni/N0yYy2/S5YhwpY676AssMbiKl0s+amvjwlA8lUr ePYDGFQnMZqZc0h1kNIY1DRYvVlC75gVwHv61YC6j6hE4vG3OU5W7UYzf Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10663"; a="321005871" X-IronPort-AV: E=Sophos;i="5.98,297,1673942400"; d="scan'208";a="321005871" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Mar 2023 08:44:19 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10663"; a="716525655" X-IronPort-AV: E=Sophos;i="5.98,297,1673942400"; d="scan'208";a="716525655" Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.24.100.114]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Mar 2023 08:44:19 -0700 Date: Tue, 28 Mar 2023 08:48:22 -0700 From: Jacob Pan To: "Tian, Kevin" Cc: Baolu Lu , LKML , "iommu@lists.linux.dev" , Jason Gunthorpe , Joerg Roedel , "dmaengine@vger.kernel.org" , "vkoul@kernel.org" , Robin Murphy , Will Deacon , "David Woodhouse" , "Raj, Ashok" , "Liu, Yi L" , "Yu, Fenghua" , "Jiang, Dave" , "Luck, Tony" , "Zanussi, Tom" , jacob.jun.pan@linux.intel.com Subject: Re: [PATCH v2 7/8] iommu: Export iommu_get_dma_domain Message-ID: <20230328084822.4b46e649@jacob-builder> In-Reply-To: References: <20230327232138.1490712-1-jacob.jun.pan@linux.intel.com> <20230327232138.1490712-8-jacob.jun.pan@linux.intel.com> Organization: OTC X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org Hi Kevin, On Tue, 28 Mar 2023 07:52:23 +0000, "Tian, Kevin" wrote: > > From: Baolu Lu > > Sent: Tuesday, March 28, 2023 2:04 PM > > > > On 3/28/23 7:21 AM, Jacob Pan wrote: > > > Devices that use ENQCMDS to submit work needs to retrieve its DMA > > > domain. It can then attach PASID to the DMA domain for shared mapping > > > (with RID) established by DMA API. > > > > > > Signed-off-by: Jacob Pan > > > --- > > > drivers/iommu/iommu.c | 1 + > > > include/linux/iommu.h | 5 +++++ > > > 2 files changed, 6 insertions(+) > > > > > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > > > index 10db680acaed..c51d343a75d2 100644 > > > --- a/drivers/iommu/iommu.c > > > +++ b/drivers/iommu/iommu.c > > > @@ -2118,6 +2118,7 @@ struct iommu_domain > > *iommu_get_dma_domain(struct device *dev) > > > { > > > return dev->iommu_group->default_domain; > > > } > > > +EXPORT_SYMBOL_GPL(iommu_get_dma_domain); > > > > Directly exporting this function for external use seems unsafe. If the > > caller is the kernel driver for this device, it's fine because default > > domain remains unchanged during the life cycle of the driver. Otherwise, > > using this function may cause UAF. Keep in mind that group's default > > domain could be changed through sysfs. > > > > However, iommu_get_domain_for_dev() has already done so and has been > > exported. Maybe I'm worried too much. :-) > > > > Agree. The kernel driver managing the device wants to get the current > domain of the device then iommu_get_domain_for_dev() is the right > interface. It knows the domain is the dma domain. This goes back to v1 then :) I thought the comments from v1 is that we don't want to check the domain type is DMA domain returned by iommu_get_domain_for_dev() If the driver "knows" the domain is dma domain, why can't it use iommu_get_dma_domain()? seems paradoxical. Thanks, Jacob