From patchwork Mon Sep 18 20:56:17 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 13390485 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 837AFCD37B0 for ; Mon, 18 Sep 2023 20:57:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230049AbjIRU5e (ORCPT ); Mon, 18 Sep 2023 16:57:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52248 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230165AbjIRU50 (ORCPT ); Mon, 18 Sep 2023 16:57:26 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AA43B12A for ; Mon, 18 Sep 2023 13:56:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1695070592; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=yLsvJ8l6b+MBG1WK2YqkwTaPRwUV38lxkQNhQoUhHr4=; b=E19Fx/avvbvCqdn2/JGbe7KJ8j8mJ0OAtWY3sHEUCv/xqTdG+50+FQBKGiZkLHTAeo2cJc vgMXsEC0TuiuEP3xRIoIph3gsICIALWlo2gOluErIkDc6umCm9MIqR8RcuT5S19YmDGs3G Y7HzgGeYWN2nsIenMXz+gVA9AbuX3tY= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-418-udjHwg-TN4W0iNphIn-i9w-1; Mon, 18 Sep 2023 16:56:27 -0400 X-MC-Unique: udjHwg-TN4W0iNphIn-i9w-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8338A3C11A00; Mon, 18 Sep 2023 20:56:26 +0000 (UTC) Received: from localhost (unknown [10.39.195.53]) by smtp.corp.redhat.com (Postfix) with ESMTP id 02F621C5BB; Mon, 18 Sep 2023 20:56:24 +0000 (UTC) From: Stefan Hajnoczi To: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Jason Gunthorpe , Alex Williamson , David Laight , "Tian, Kevin" , Stefan Hajnoczi , Jason Gunthorpe Subject: [PATCH v3 3/3] vfio: use __aligned_u64 in struct vfio_device_ioeventfd Date: Mon, 18 Sep 2023 16:56:17 -0400 Message-ID: <20230918205617.1478722-4-stefanha@redhat.com> In-Reply-To: <20230918205617.1478722-1-stefanha@redhat.com> References: <20230918205617.1478722-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org The memory layout of struct vfio_device_ioeventfd is architecture-dependent due to a u64 field and a struct size that is not a multiple of 8 bytes: - On x86_64 the struct size is padded to a multiple of 8 bytes. - On x32 the struct size is only a multiple of 4 bytes, not 8. - Other architectures may vary. Use __aligned_u64 to make memory layout consistent. This reduces the chance that 32-bit userspace on a 64-bit kernel breakage. This patch increases the struct size on x32 but this is safe because of the struct's argsz field. The kernel may grow the struct as long as it still supports smaller argsz values from userspace (e.g. applications compiled against older kernel headers). The code that uses struct vfio_device_ioeventfd already works correctly when the struct size grows, so only the struct definition needs to be changed. Suggested-by: Jason Gunthorpe Reviewed-by: Jason Gunthorpe Reviewed-by: Kevin Tian Signed-off-by: Stefan Hajnoczi --- include/uapi/linux/vfio.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h index ee98b6d4a112..049ce8065a32 100644 --- a/include/uapi/linux/vfio.h +++ b/include/uapi/linux/vfio.h @@ -864,9 +864,10 @@ struct vfio_device_ioeventfd { #define VFIO_DEVICE_IOEVENTFD_32 (1 << 2) /* 4-byte write */ #define VFIO_DEVICE_IOEVENTFD_64 (1 << 3) /* 8-byte write */ #define VFIO_DEVICE_IOEVENTFD_SIZE_MASK (0xf) - __u64 offset; /* device fd offset of write */ - __u64 data; /* data to be written */ + __aligned_u64 offset; /* device fd offset of write */ + __aligned_u64 data; /* data to be written */ __s32 fd; /* -1 for de-assignment */ + __u32 reserved; }; #define VFIO_DEVICE_IOEVENTFD _IO(VFIO_TYPE, VFIO_BASE + 16)