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 EE000C433EF for ; Wed, 2 Mar 2022 16:29:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241954AbiCBQ3z (ORCPT ); Wed, 2 Mar 2022 11:29:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34344 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241674AbiCBQ3y (ORCPT ); Wed, 2 Mar 2022 11:29:54 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id B62BD40E5F for ; Wed, 2 Mar 2022 08:29:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1646238548; 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=4JYBVP71dm6qwHu1wwd1S6iPhE9b42/h7o81Qtmexmg=; b=SwVehJPL31yFdAh2MMoLz/v8nHvs2H48IBFxaNoXUO4qQtazu0igoeH4fFgIdDZGr9Dcvp d73PKZwVhNjVtzYNvlk5Z4ZowsVmcxIs7oPedPzo3UWPcJ/D0runLsoR6Bg1LZ7qvqXAN9 xUX9tF5UqN6EB5czkXFp7RY9QjechII= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-235-q_RXSMVRN5ad-zDxFjgBYQ-1; Wed, 02 Mar 2022 11:29:07 -0500 X-MC-Unique: q_RXSMVRN5ad-zDxFjgBYQ-1 Received: by mail-wm1-f70.google.com with SMTP id f12-20020a7bcd0c000000b00384993440cfso786045wmj.3 for ; Wed, 02 Mar 2022 08:29:07 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=4JYBVP71dm6qwHu1wwd1S6iPhE9b42/h7o81Qtmexmg=; b=NxQK6Z/FnbG++GQiqUlzaS2uWYUc1+MAosmbl71xYpxoeRrI83WIDeSfZnO9EP8tt8 UIO8IWJaD9uB1IaeXLtE46IxYHuniDF8cGmH6paoZbXxMg/Em1qxnihIE5CoiTvukb6t SAc3DrKd4L3R5Tvpg5edP7js0WvRlsYtkAay5I7edmoX7dfDsmoz+y81kArf/CB6PuHk BE3l9WzvGgsz1XkufnRyWTx2iFqMKlFpmO8DHH2hTqvzaCU92jfuoMOEHrUBSTt9eZMI EPVPYXZZUz4lkcdfZ2MVO6OMAlYLQpNDrv5FoHhoMUtc+6WiyBTaII0n0o5cQK1fM+Wi rcfg== X-Gm-Message-State: AOAM532vAXVVOxRGKdpcZvgyfjQawvpBdRpOq771YQGiYaZK8Vq1CXz8 OFD0Fmji/g+iTTu4Hr4fuNqc/Bcj/GpVK2SR5UyWWrhFilY5VgzL9WM3nXTBC4opFD3vqtw3oas n+Gc5kF3fMPJtKGPzOarG1xs3 X-Received: by 2002:a5d:56cd:0:b0:1ee:3248:525b with SMTP id m13-20020a5d56cd000000b001ee3248525bmr21677358wrw.124.1646238546609; Wed, 02 Mar 2022 08:29:06 -0800 (PST) X-Google-Smtp-Source: ABdhPJwnuzpoqkxUXsedIQ3mO7DVJwgzjOmZC8iKKjQtEy+lCllqu+K+PPeU8AEGxPiyGzG6Giw9Sw== X-Received: by 2002:a5d:56cd:0:b0:1ee:3248:525b with SMTP id m13-20020a5d56cd000000b001ee3248525bmr21677329wrw.124.1646238546364; Wed, 02 Mar 2022 08:29:06 -0800 (PST) Received: from redhat.com ([2a10:8006:355c:0:48d6:b937:2fb9:b7de]) by smtp.gmail.com with ESMTPSA id m18-20020a5d56d2000000b001edc00dbeeasm16594955wrw.69.2022.03.02.08.29.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Mar 2022 08:29:05 -0800 (PST) Date: Wed, 2 Mar 2022 11:29:02 -0500 From: "Michael S. Tsirkin" To: "Jason A. Donenfeld" Cc: Laszlo Ersek , LKML , KVM list , QEMU Developers , linux-hyperv@vger.kernel.org, Linux Crypto Mailing List , Alexander Graf , "Michael Kelley (LINUX)" , Greg Kroah-Hartman , adrian@parity.io, Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Dominik Brodowski , Jann Horn , "Rafael J. Wysocki" , "Brown, Len" , Pavel Machek , Linux PM , Colm MacCarthaigh , Theodore Ts'o , Arnd Bergmann Subject: Re: propagating vmgenid outward and upward Message-ID: <20220302112258-mutt-send-email-mst@kernel.org> References: <20220301121419-mutt-send-email-mst@kernel.org> <20220302031738-mutt-send-email-mst@kernel.org> <20220302074503-mutt-send-email-mst@kernel.org> <20220302092149-mutt-send-email-mst@kernel.org> <20220302101602-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Wed, Mar 02, 2022 at 04:36:49PM +0100, Jason A. Donenfeld wrote: > Hi Michael, > > On Wed, Mar 02, 2022 at 10:20:25AM -0500, Michael S. Tsirkin wrote: > > So writing some code: > > > > 1: > > put plaintext in a buffer > > put a key in a buffer > > put the nonce for that encryption in a buffer > > > > if vm gen id != stored vm gen id > > stored vm gen id = vm gen id > > goto 1 > > > > I think this is race free, but I don't see why does it matter whether we > > read gen id atomically or not. > > Because that 16 byte read of vmgenid is not atomic. Let's say you read > the first 8 bytes, and then the VM is forked. In the forked VM, the next > 8 bytes are the same as last time, but the first 8 bytes, which you > already read, have changed. In that case, your != becomes a ==, and the > test fails. > > This is one of those fundamental things of "unique ID" vs "generation > counter word". > > Anyway, per your request in your last email, I wrote some code for this, > which may or may not be totally broken, and only works on 64-bit x86, > which is really the best possible case in terms of performance. And even > so, it's not great. > > Jason > > --------8<------------------------ > > diff --git a/drivers/net/wireguard/noise.c b/drivers/net/wireguard/noise.c > index 720952b92e78..250b8973007d 100644 > --- a/drivers/net/wireguard/noise.c > +++ b/drivers/net/wireguard/noise.c > @@ -106,6 +106,7 @@ static struct noise_keypair *keypair_create(struct wg_peer *peer) > keypair->entry.type = INDEX_HASHTABLE_KEYPAIR; > keypair->entry.peer = peer; > kref_init(&keypair->refcount); > + keypair->vmgenid = vmgenid_read_atomic(); > return keypair; > } > > diff --git a/drivers/net/wireguard/noise.h b/drivers/net/wireguard/noise.h > index c527253dba80..0add240a14a0 100644 > --- a/drivers/net/wireguard/noise.h > +++ b/drivers/net/wireguard/noise.h > @@ -27,10 +27,13 @@ struct noise_symmetric_key { > bool is_valid; > }; > > +extern __uint128_t vmgenid_read_atomic(void); > + > struct noise_keypair { > struct index_hashtable_entry entry; > struct noise_symmetric_key sending; > atomic64_t sending_counter; > + __uint128_t vmgenid; > struct noise_symmetric_key receiving; > struct noise_replay_counter receiving_counter; > __le32 remote_index; > diff --git a/drivers/net/wireguard/send.c b/drivers/net/wireguard/send.c > index 5368f7c35b4b..40d016be59e3 100644 > --- a/drivers/net/wireguard/send.c > +++ b/drivers/net/wireguard/send.c > @@ -381,6 +381,9 @@ void wg_packet_send_staged_packets(struct wg_peer *peer) > goto out_invalid; > } > > + if (keypair->vmgenid != vmgenid_read_atomic()) > + goto out_invalid; > + > packets.prev->next = NULL; > wg_peer_get(keypair->entry.peer); > PACKET_CB(packets.next)->keypair = keypair; I don't think we care about an atomic read here. All data is in buffer by this point, if it did not fork before that then we are ok, even if it forks during the read. We probably do need a memory barrier to make sure all writes complete before the read of vmgenid, I'm not sure which kind - I think hypervisor can be trusted to do a full CPU barrier on fork so probably just a compiler barrier. > diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c > index 0ae1a39f2e28..c122fae1d494 100644 > --- a/drivers/virt/vmgenid.c > +++ b/drivers/virt/vmgenid.c > @@ -21,6 +21,21 @@ struct vmgenid_state { > u8 this_id[VMGENID_SIZE]; > }; > > +static __uint128_t *val; > + > +__uint128_t vmgenid_read_atomic(void) > +{ > + __uint128_t ret = 0; > + if (!val) > + return 0; > + asm volatile("lock cmpxchg16b %1" > + : "+A"(ret) > + : "m"(*val), "b"(0), "c"(0) > + : "cc"); > + return ret; > +} > +EXPORT_SYMBOL(vmgenid_read_atomic); > + > static int vmgenid_add(struct acpi_device *device) > { > struct acpi_buffer parsed = { ACPI_ALLOCATE_BUFFER }; > @@ -50,6 +65,7 @@ static int vmgenid_add(struct acpi_device *device) > phys_addr = (obj->package.elements[0].integer.value << 0) | > (obj->package.elements[1].integer.value << 32); > state->next_id = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB); > + val = (__uint128_t *)state->next_id; > if (IS_ERR(state->next_id)) { > ret = PTR_ERR(state->next_id); > goto out; 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 40F77C433F5 for ; Wed, 2 Mar 2022 16:34:09 +0000 (UTC) Received: from localhost ([::1]:48860 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nPRvU-0002s5-8Q for qemu-devel@archiver.kernel.org; Wed, 02 Mar 2022 11:34:08 -0500 Received: from eggs.gnu.org ([209.51.188.92]:60390) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nPRqh-0003nb-Vl for qemu-devel@nongnu.org; Wed, 02 Mar 2022 11:29:12 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:25283) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nPRqg-00005f-8q for qemu-devel@nongnu.org; Wed, 02 Mar 2022 11:29:11 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1646238549; 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=4JYBVP71dm6qwHu1wwd1S6iPhE9b42/h7o81Qtmexmg=; b=YX40hjXQQxCKpwxmYcSumGmf2tAocVIp+/c5FmiSv4UWOuLteu2kPCWnQS8pHZFPrRO+cX alNpmMPES3Sb7FW+bmT33i0EKjSVezEr0WCsXxXyMsMIETffdUM57N1TDvYKvJU3NfEitj sbku/SlfnJ/q0MM3MpjU1dh7ZdnH6uc= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-18-AAJiZd3BNrWU2rYRoAF6zA-1; Wed, 02 Mar 2022 11:29:08 -0500 X-MC-Unique: AAJiZd3BNrWU2rYRoAF6zA-1 Received: by mail-wm1-f69.google.com with SMTP id ay7-20020a05600c1e0700b003813d7a7d03so1009010wmb.1 for ; Wed, 02 Mar 2022 08:29:08 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=4JYBVP71dm6qwHu1wwd1S6iPhE9b42/h7o81Qtmexmg=; b=j2rt/ZAJZPJb1/Uui4hiF6ieLG7ugVoeTdL/gtJqDz12pr/b97YwM68G1eiytjg4NF jfI71Iyvp7dTFq07eeR0nopziWzgGkm/TSg7an1BOaCx/vnN+Q0GhzK/ywmvLrZqWkq5 XXysKNxfD04t28+B4J4O5e3VBkQDa7iFo3lt1JHNdNXEq+Mv59Nk5gxIrlOlFKwklSjn d0mqPv48yBkb1J0GW113q/VlNuvpEkKQFf8j1ek3WcqD5LEgjA2+jfTe06NUQ9j+iiP1 8vr+T2tPUYGPBas6cZ/JwsKK0o80Zygjs2G4o/MKtNdbJmqU105qeMRHjq7Y2sKpMto8 BLnw== X-Gm-Message-State: AOAM532bss0VlvjWLDu6Q4BSpLRFsVgM5z244YLNWTVlLEQ1oWmA7/32 /HrRCm+C0g4umg61p/IgXjx3ymGQsxW3wHWPa+67x28zO8wlli5eIyZTP1ScgPce3IdbbIezrrL oxzHKWXgaPavrMUQ= X-Received: by 2002:a5d:56cd:0:b0:1ee:3248:525b with SMTP id m13-20020a5d56cd000000b001ee3248525bmr21677360wrw.124.1646238546613; Wed, 02 Mar 2022 08:29:06 -0800 (PST) X-Google-Smtp-Source: ABdhPJwnuzpoqkxUXsedIQ3mO7DVJwgzjOmZC8iKKjQtEy+lCllqu+K+PPeU8AEGxPiyGzG6Giw9Sw== X-Received: by 2002:a5d:56cd:0:b0:1ee:3248:525b with SMTP id m13-20020a5d56cd000000b001ee3248525bmr21677329wrw.124.1646238546364; Wed, 02 Mar 2022 08:29:06 -0800 (PST) Received: from redhat.com ([2a10:8006:355c:0:48d6:b937:2fb9:b7de]) by smtp.gmail.com with ESMTPSA id m18-20020a5d56d2000000b001edc00dbeeasm16594955wrw.69.2022.03.02.08.29.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Mar 2022 08:29:05 -0800 (PST) Date: Wed, 2 Mar 2022 11:29:02 -0500 From: "Michael S. Tsirkin" To: "Jason A. Donenfeld" Subject: Re: propagating vmgenid outward and upward Message-ID: <20220302112258-mutt-send-email-mst@kernel.org> References: <20220301121419-mutt-send-email-mst@kernel.org> <20220302031738-mutt-send-email-mst@kernel.org> <20220302074503-mutt-send-email-mst@kernel.org> <20220302092149-mutt-send-email-mst@kernel.org> <20220302101602-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Brown, Len" , linux-hyperv@vger.kernel.org, Colm MacCarthaigh , Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , adrian@parity.io, KVM list , Jann Horn , Greg Kroah-Hartman , Linux PM , "Rafael J. Wysocki" , LKML , Dominik Brodowski , QEMU Developers , Alexander Graf , Linux Crypto Mailing List , Pavel Machek , Theodore Ts'o , "Michael Kelley \(LINUX\)" , Laszlo Ersek , Arnd Bergmann Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Mar 02, 2022 at 04:36:49PM +0100, Jason A. Donenfeld wrote: > Hi Michael, > > On Wed, Mar 02, 2022 at 10:20:25AM -0500, Michael S. Tsirkin wrote: > > So writing some code: > > > > 1: > > put plaintext in a buffer > > put a key in a buffer > > put the nonce for that encryption in a buffer > > > > if vm gen id != stored vm gen id > > stored vm gen id = vm gen id > > goto 1 > > > > I think this is race free, but I don't see why does it matter whether we > > read gen id atomically or not. > > Because that 16 byte read of vmgenid is not atomic. Let's say you read > the first 8 bytes, and then the VM is forked. In the forked VM, the next > 8 bytes are the same as last time, but the first 8 bytes, which you > already read, have changed. In that case, your != becomes a ==, and the > test fails. > > This is one of those fundamental things of "unique ID" vs "generation > counter word". > > Anyway, per your request in your last email, I wrote some code for this, > which may or may not be totally broken, and only works on 64-bit x86, > which is really the best possible case in terms of performance. And even > so, it's not great. > > Jason > > --------8<------------------------ > > diff --git a/drivers/net/wireguard/noise.c b/drivers/net/wireguard/noise.c > index 720952b92e78..250b8973007d 100644 > --- a/drivers/net/wireguard/noise.c > +++ b/drivers/net/wireguard/noise.c > @@ -106,6 +106,7 @@ static struct noise_keypair *keypair_create(struct wg_peer *peer) > keypair->entry.type = INDEX_HASHTABLE_KEYPAIR; > keypair->entry.peer = peer; > kref_init(&keypair->refcount); > + keypair->vmgenid = vmgenid_read_atomic(); > return keypair; > } > > diff --git a/drivers/net/wireguard/noise.h b/drivers/net/wireguard/noise.h > index c527253dba80..0add240a14a0 100644 > --- a/drivers/net/wireguard/noise.h > +++ b/drivers/net/wireguard/noise.h > @@ -27,10 +27,13 @@ struct noise_symmetric_key { > bool is_valid; > }; > > +extern __uint128_t vmgenid_read_atomic(void); > + > struct noise_keypair { > struct index_hashtable_entry entry; > struct noise_symmetric_key sending; > atomic64_t sending_counter; > + __uint128_t vmgenid; > struct noise_symmetric_key receiving; > struct noise_replay_counter receiving_counter; > __le32 remote_index; > diff --git a/drivers/net/wireguard/send.c b/drivers/net/wireguard/send.c > index 5368f7c35b4b..40d016be59e3 100644 > --- a/drivers/net/wireguard/send.c > +++ b/drivers/net/wireguard/send.c > @@ -381,6 +381,9 @@ void wg_packet_send_staged_packets(struct wg_peer *peer) > goto out_invalid; > } > > + if (keypair->vmgenid != vmgenid_read_atomic()) > + goto out_invalid; > + > packets.prev->next = NULL; > wg_peer_get(keypair->entry.peer); > PACKET_CB(packets.next)->keypair = keypair; I don't think we care about an atomic read here. All data is in buffer by this point, if it did not fork before that then we are ok, even if it forks during the read. We probably do need a memory barrier to make sure all writes complete before the read of vmgenid, I'm not sure which kind - I think hypervisor can be trusted to do a full CPU barrier on fork so probably just a compiler barrier. > diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c > index 0ae1a39f2e28..c122fae1d494 100644 > --- a/drivers/virt/vmgenid.c > +++ b/drivers/virt/vmgenid.c > @@ -21,6 +21,21 @@ struct vmgenid_state { > u8 this_id[VMGENID_SIZE]; > }; > > +static __uint128_t *val; > + > +__uint128_t vmgenid_read_atomic(void) > +{ > + __uint128_t ret = 0; > + if (!val) > + return 0; > + asm volatile("lock cmpxchg16b %1" > + : "+A"(ret) > + : "m"(*val), "b"(0), "c"(0) > + : "cc"); > + return ret; > +} > +EXPORT_SYMBOL(vmgenid_read_atomic); > + > static int vmgenid_add(struct acpi_device *device) > { > struct acpi_buffer parsed = { ACPI_ALLOCATE_BUFFER }; > @@ -50,6 +65,7 @@ static int vmgenid_add(struct acpi_device *device) > phys_addr = (obj->package.elements[0].integer.value << 0) | > (obj->package.elements[1].integer.value << 32); > state->next_id = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB); > + val = (__uint128_t *)state->next_id; > if (IS_ERR(state->next_id)) { > ret = PTR_ERR(state->next_id); > goto out;