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=-10.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 32472C2BA1A for ; Tue, 7 Apr 2020 01:08:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 04A1820719 for ; Tue, 7 Apr 2020 01:08:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="VbnKDal2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726799AbgDGBIO (ORCPT ); Mon, 6 Apr 2020 21:08:14 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:35934 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726668AbgDGBH4 (ORCPT ); Mon, 6 Apr 2020 21:07:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1586221675; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=b+P99eoGOE59dzJri6nDdYTRF/iHp1rUM821OiEBSWI=; b=VbnKDal2mW3x/8uUyaF/BmNOSYJhExtZEV+4YPbdf2MotyPb8XTuUwVhMq6iT+0p7sRLN8 X8tHVPtNtNJkdwDWBJ5XrTtic8SPeS8FaCWedB6SlASJbpDexktmz2LxsFDt6TMKVRn7/g efMH/vzxsVniMRICtNnUv8wdzO0RK7Q= Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-358-rkvNepdsNvOIIbonyTSGUA-1; Mon, 06 Apr 2020 21:07:51 -0400 X-MC-Unique: rkvNepdsNvOIIbonyTSGUA-1 Received: by mail-wr1-f71.google.com with SMTP id c8so837794wru.20 for ; Mon, 06 Apr 2020 18:07:50 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=b+P99eoGOE59dzJri6nDdYTRF/iHp1rUM821OiEBSWI=; b=i3oCbjoXOk6nPnSmE1xkBViwP6Auv278cQpHLyG280W0VpAQ7se1/inHc+2Scz1s1Q KKSR5WB5YG5kVEHXqpV1l1UakvSMMc+gmuO1rwITriEkMKs8woredBt3OQA06JOBeUW3 x6146E5Q9+sZdfuJd8jLIqhAc6bhbT1MIChtCuiZW/zU4lPDrKyHbtkR5SyRe6UwWdO5 RqaMS+6sipaWKSdmEXDsTUE+gz01BCM28TlJho3Rxa2OVdHGbUGtF2HPSSNheDkIhJfI LIkWuo+zE4Lxy1Ra8lS+SxDt/e0klgGQEmRtGFhO2aKowM/BQqXMaezrJU+qa7hzOJfm oFnw== X-Gm-Message-State: AGi0PuZzrfiridHEcegdbvVepZ5QNHSOurSietbbuB+o6Am6QVaPNb8d MT6sEqpXc9w1UiDhAJ1nNtpPw1ZIJyDO4sbQH/FhcuhColWAqgZIByhIqLhWNzI1Y2egE9qCfxp twyZF4Cs0tyALkX2EdtHCFYUY X-Received: by 2002:adf:f98b:: with SMTP id f11mr1998834wrr.259.1586221669694; Mon, 06 Apr 2020 18:07:49 -0700 (PDT) X-Google-Smtp-Source: APiQypJ7vAsHxvjmiu+bo7NHbyExOgBSbxXMZd7IkvuAC9tnfoRSEzkPJmWDYEX8+2JgtuNqELnN8w== X-Received: by 2002:adf:f98b:: with SMTP id f11mr1998816wrr.259.1586221669436; Mon, 06 Apr 2020 18:07:49 -0700 (PDT) Received: from redhat.com (bzq-79-176-51-222.red.bezeqint.net. [79.176.51.222]) by smtp.gmail.com with ESMTPSA id j11sm28630487wrt.14.2020.04.06.18.07.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Apr 2020 18:07:48 -0700 (PDT) Date: Mon, 6 Apr 2020 21:07:47 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: Jason Wang , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org Subject: [PATCH v7 10/19] vhost: force spec specified alignment on types Message-ID: <20200407010700.446571-11-mst@redhat.com> References: <20200407010700.446571-1-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200407010700.446571-1-mst@redhat.com> X-Mailer: git-send-email 2.24.1.751.gd10ce2899c X-Mutt-Fcc: =sent Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The ring element addresses are passed between components with different alignments assumptions. Thus, if guest/userspace selects a pointer and host then gets and dereferences it, we might need to decrease the compiler-selected alignment to prevent compiler on the host from assuming pointer is aligned. This actually triggers on ARM with -mabi=apcs-gnu - which is a deprecated configuration, but it seems safer to handle this generally. I verified that the produced binary is exactly identical on x86. Signed-off-by: Michael S. Tsirkin --- drivers/vhost/vhost.h | 6 +++--- include/linux/virtio_ring.h | 24 +++++++++++++++++++++--- 2 files changed, 24 insertions(+), 6 deletions(-) diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index f8403bd46b85..60cab4c78229 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -67,9 +67,9 @@ struct vhost_virtqueue { /* The actual ring of buffers. */ struct mutex mutex; unsigned int num; - struct vring_desc __user *desc; - struct vring_avail __user *avail; - struct vring_used __user *used; + vring_desc_t __user *desc; + vring_avail_t __user *avail; + vring_used_t __user *used; const struct vhost_iotlb_map *meta_iotlb[VHOST_NUM_ADDRS]; struct file *kick; struct eventfd_ctx *call_ctx; diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h index 11680e74761a..c3f9ca054250 100644 --- a/include/linux/virtio_ring.h +++ b/include/linux/virtio_ring.h @@ -60,14 +60,32 @@ static inline void virtio_store_mb(bool weak_barriers, struct virtio_device; struct virtqueue; +/* + * The ring element addresses are passed between components with different + * alignments assumptions. Thus, we might need to decrease the compiler-selected + * alignment, and so must use a typedef to make sure the __aligned attribute + * actually takes hold: + * + * https://gcc.gnu.org/onlinedocs//gcc/Common-Type-Attributes.html#Common-Type-Attributes + * + * When used on a struct, or struct member, the aligned attribute can only + * increase the alignment; in order to decrease it, the packed attribute must + * be specified as well. When used as part of a typedef, the aligned attribute + * can both increase and decrease alignment, and specifying the packed + * attribute generates a warning. + */ +typedef struct vring_desc __aligned(VRING_DESC_ALIGN_SIZE) vring_desc_t; +typedef struct vring_avail __aligned(VRING_AVAIL_ALIGN_SIZE) vring_avail_t; +typedef struct vring_used __aligned(VRING_USED_ALIGN_SIZE) vring_used_t; + struct vring { unsigned int num; - struct vring_desc *desc; + vring_desc_t *desc; - struct vring_avail *avail; + vring_avail_t *avail; - struct vring_used *used; + vring_used_t *used; }; /* -- MST