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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 7598AC76188 for ; Mon, 22 Jul 2019 15:33:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4785421921 for ; Mon, 22 Jul 2019 15:33:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729247AbfGVPdv (ORCPT ); Mon, 22 Jul 2019 11:33:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37046 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728794AbfGVPdu (ORCPT ); Mon, 22 Jul 2019 11:33:50 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 60CEE307D915; Mon, 22 Jul 2019 15:33:50 +0000 (UTC) Received: from redhat.com (ovpn-124-54.rdu2.redhat.com [10.10.124.54]) by smtp.corp.redhat.com (Postfix) with SMTP id 786F95D968; Mon, 22 Jul 2019 15:33:44 +0000 (UTC) Date: Mon, 22 Jul 2019 11:33:35 -0400 From: "Michael S. Tsirkin" To: Eric Auger Cc: eric.auger.pro@gmail.com, hch@lst.de, m.szyprowski@samsung.com, robin.murphy@arm.com, jasowang@redhat.com, virtualization@lists.linux-foundation.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] virtio/virtio_ring: Fix the dma_max_mapping_size call Message-ID: <20190722112704-mutt-send-email-mst@kernel.org> References: <20190722145509.1284-1-eric.auger@redhat.com> <20190722145509.1284-3-eric.auger@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190722145509.1284-3-eric.auger@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.48]); Mon, 22 Jul 2019 15:33:50 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 22, 2019 at 04:55:09PM +0200, Eric Auger wrote: > Do not call dma_max_mapping_size for devices that have no DMA > mask set, otherwise we can hit a NULL pointer dereference. > > This occurs when a virtio-blk-pci device is protected with > a virtual IOMMU. > > Fixes: e6d6dd6c875e ("virtio: Introduce virtio_max_dma_size()") > Signed-off-by: Eric Auger > Suggested-by: Christoph Hellwig Christoph, I wonder why did you suggest this? The connection between dma_mask and dma_max_mapping_size is far from obvious. The documentation doesn't exist. Do we really have to teach all users about this hack? Why not just make dma_max_mapping_size DTRT? > --- > drivers/virtio/virtio_ring.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index c8be1c4f5b55..37c143971211 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -262,7 +262,7 @@ size_t virtio_max_dma_size(struct virtio_device *vdev) > { > size_t max_segment_size = SIZE_MAX; > > - if (vring_use_dma_api(vdev)) > + if (vring_use_dma_api(vdev) && vdev->dev.dma_mask) > max_segment_size = dma_max_mapping_size(&vdev->dev); > > return max_segment_size; > -- > 2.20.1