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 9A5A7C433F5 for ; Wed, 24 Nov 2021 02:33:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240751AbhKXCgw (ORCPT ); Tue, 23 Nov 2021 21:36:52 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:40690 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231824AbhKXCgv (ORCPT ); Tue, 23 Nov 2021 21:36:51 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1637721222; 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=UTD0jVelqh1qLoZ9FHw+tRPzQL6rQcuJQVst1x7Zk+E=; b=TNe7mU/lKfz0QPMtotvkfI0ulah59EFkbz6awaNofRB3LhujUpUwNWh8jxLZxMUXziE+Du KRjAJvKCO6I+gQCOTzGIxEXfmzSs2CRoqwz/zc1Ms+21wOoaIxt6IksUjLVyNwrY1Ceslm K5X+xyr306QiegkRB11ZcSM5pVtzZY8= Received: from mail-lf1-f71.google.com (mail-lf1-f71.google.com [209.85.167.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-434-jj0seEK1OEaxPrwZCkGZ5Q-1; Tue, 23 Nov 2021 21:33:40 -0500 X-MC-Unique: jj0seEK1OEaxPrwZCkGZ5Q-1 Received: by mail-lf1-f71.google.com with SMTP id k5-20020a05651210c500b0040934a07fbdso599633lfg.22 for ; Tue, 23 Nov 2021 18:33:40 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=UTD0jVelqh1qLoZ9FHw+tRPzQL6rQcuJQVst1x7Zk+E=; b=5ClSDgaF7CUe0raqnKGtVgMeSS1W6BZzVhCxo86Hp2oA+OCw2ectVRofmTTDDsOCGN 8kXz25UJ5N6JQMMTdQ+JcqH8GV/fdA8HrGTsLDgBQ+7MJc1QbDe/AawjJ53g1m1grhyL rVu0uHFUiYoJAtR6HdnM4+umU8+wnrtOpk8JTbb44ffCTTQkAk8PceuMBQqMtzIvHop3 ZPUFPsVMA82Mt78oymEYfLp5eOl0S4QmUMVpNLNNpd6qYNRHxW0jqMIH8ZnhP3vjNBKM T9re6juu6ofDfIacOOZf3OhJEblaWs7tKYiljVFGS5QY5HeJqOj56mfZs4ivbzkAjYxb k/8g== X-Gm-Message-State: AOAM531Q5CxyvcOWwkbhjVv9aLtnR8u4WzrkRQwmyjzOgXzcOmSlHRyp DYpJksdtmfdxJFaiZEBfeR1uTeO6KK+kjPaXL0oVaXXxHKBYLE6KMenbIbwPQ2ttEq/4b6Sag/P 67kDKRKor6peEud+pvfkjn9+xP2OdkJ1kvJzqKVul X-Received: by 2002:ac2:5310:: with SMTP id c16mr10809341lfh.580.1637721219293; Tue, 23 Nov 2021 18:33:39 -0800 (PST) X-Google-Smtp-Source: ABdhPJzJWRacun7W/BHsQL8YnMJOFffJa/FKnSoaoTDtgeSr1Mt6ke2qFcv4Usp7jKaQufiJXnZP+xRPr9o6CDcyZ8k= X-Received: by 2002:ac2:5310:: with SMTP id c16mr10809303lfh.580.1637721219040; Tue, 23 Nov 2021 18:33:39 -0800 (PST) MIME-Version: 1.0 References: <20211027022107.14357-1-jasowang@redhat.com> <20211027022107.14357-2-jasowang@redhat.com> <20211119160951.5f2294c8.pasic@linux.ibm.com> <20211122063518.37929c01.pasic@linux.ibm.com> <20211122064922.51b3678e.pasic@linux.ibm.com> <20211122212352.4a76232d.pasic@linux.ibm.com> <20211123055906-mutt-send-email-mst@kernel.org> <87zgpupcga.fsf@mpe.ellerman.id.au> In-Reply-To: From: Jason Wang Date: Wed, 24 Nov 2021 10:33:28 +0800 Message-ID: Subject: Re: [PATCH V5 1/4] virtio_ring: validate used buffer length To: Michael Ellerman Cc: "Michael S. Tsirkin" , Halil Pasic , virtualization , "Hetzelt, Felicitas" , linux-kernel , "kaplan, david" , Konrad Rzeszutek Wilk , Stefan Hajnoczi , Stefano Garzarella , mcgrof@kernel.org, David Hildenbrand Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 24, 2021 at 10:26 AM Jason Wang wrote: > > On Wed, Nov 24, 2021 at 9:30 AM Michael Ellerman wrote: > > > > "Michael S. Tsirkin" writes: > > > On Tue, Nov 23, 2021 at 10:25:20AM +0800, Jason Wang wrote: > > >> On Tue, Nov 23, 2021 at 4:24 AM Halil Pasic wrote: > > >> > > > >> > On Mon, 22 Nov 2021 14:25:26 +0800 > > >> > Jason Wang wrote: > > >> > > > >> > > I think the fixes are: > > >> > > > > >> > > 1) fixing the vhost vsock > > >> > > 2) use suppress_used_validation=true to let vsock driver to validate > > >> > > the in buffer length > > >> > > 3) probably a new feature so the driver can only enable the validation > > >> > > when the feature is enabled. > > >> > > > >> > I'm not sure, I would consider a F_DEV_Y_FIXED_BUG_X a perfectly good > > >> > feature. Frankly the set of such bugs is device implementation > > >> > specific and it makes little sense to specify a feature bit > > >> > that says the device implementation claims to adhere to some > > >> > aspect of the specification. Also what would be the semantic > > >> > of not negotiating F_DEV_Y_FIXED_BUG_X? > > >> > > >> Yes, I agree. Rethink of the feature bit, it seems unnecessary, > > >> especially considering the driver should not care about the used > > >> length for tx. > > >> > > >> > > > >> > On the other hand I see no other way to keep the validation > > >> > permanently enabled for fixed implementations, and get around the problem > > >> > with broken implementations. So we could have something like > > >> > VHOST_USED_LEN_STRICT. > > >> > > >> It's more about a choice of the driver's knowledge. For vsock TX it > > >> should be fine. If we introduce a parameter and disable it by default, > > >> it won't be very useful. > > >> > > >> > > > >> > Maybe, we can also think of 'warn and don't alter behavior' instead of > > >> > 'warn' and alter behavior. Or maybe even not having such checks on in > > >> > production, but only when testing. > > >> > > >> I think there's an agreement that virtio drivers need more hardening, > > >> that's why a lot of patches were merged. Especially considering the > > >> new requirements came from confidential computing, smart NIC and > > >> VDUSE. For virtio drivers, enabling the validation may help to > > >> > > >> 1) protect the driver from the buggy and malicious device > > >> 2) uncover the bugs of the devices (as vsock did, and probably rpmsg) > > >> 3) force the have a smart driver that can do the validation itself > > >> then we can finally remove the validation in the core > > >> > > >> So I'd like to keep it enabled. > > >> > > >> Thanks > > > > > > Let's see how far we can get. But yes, maybe we were too aggressive in > > > breaking things by default, a warning might be a better choice for a > > > couple of cycles. > > Ok, considering we saw the issues with balloons I think I can post a > patch to use warn instead. I wonder if we need to taint the kernel in > this case. Rethink this, consider we still have some time, I tend to convert the drivers to validate the length by themselves. Does this make sense? Thanks > > > > > This series appears to break the virtio_balloon driver as well. > > > > The symptom is soft lockup warnings, eg: > > > > INFO: task kworker/1:1:109 blocked for more than 614 seconds. > > Not tainted 5.16.0-rc2-gcc-10.3.0 #21 > > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > > task:kworker/1:1 state:D stack:12496 pid: 109 ppid: 2 flags:0x00000800 > > Workqueue: events_freezable update_balloon_size_func > > Call Trace: > > [c000000003cef7c0] [c000000003cef820] 0xc000000003cef820 (unreliable) > > [c000000003cef9b0] [c00000000001e238] __switch_to+0x1e8/0x2f0 > > [c000000003cefa10] [c000000000f0a00c] __schedule+0x2cc/0xb50 > > [c000000003cefae0] [c000000000f0a8fc] schedule+0x6c/0x140 > > [c000000003cefb10] [c00000000095b6c4] tell_host+0xe4/0x130 > > [c000000003cefba0] [c00000000095d234] update_balloon_size_func+0x394/0x3f0 > > [c000000003cefc70] [c000000000178064] process_one_work+0x2c4/0x5b0 > > [c000000003cefd10] [c0000000001783f8] worker_thread+0xa8/0x640 > > [c000000003cefda0] [c000000000185444] kthread+0x1b4/0x1c0 > > [c000000003cefe10] [c00000000000cee4] ret_from_kernel_thread+0x5c/0x64 > > > > Similar backtrace reported here by Luis: > > > > https://lore.kernel.org/lkml/YY2duTi0wAyAKUTJ@bombadil.infradead.org/ > > > > Bisect points to: > > > > # first bad commit: [939779f5152d161b34f612af29e7dc1ac4472fcf] virtio_ring: validate used buffer length > > > > Adding suppress used validation to the virtio balloon driver "fixes" it, eg. > > > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > > index c22ff0117b46..a14b82ceebb2 100644 > > --- a/drivers/virtio/virtio_balloon.c > > +++ b/drivers/virtio/virtio_balloon.c > > @@ -1150,6 +1150,7 @@ static unsigned int features[] = { > > }; > > > > static struct virtio_driver virtio_balloon_driver = { > > + .suppress_used_validation = true, > > .feature_table = features, > > .feature_table_size = ARRAY_SIZE(features), > > .driver.name = KBUILD_MODNAME, > > Looks good, we need a formal patch for this. > > And we need fix Qemu as well which advertise non zero used length for > inflate/deflate queue: > > static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq) > ... > virtqueue_push(vq, elem, offset); > > Thanks > > > > > > > cheers > > 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 smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (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 88A97C433F5 for ; Wed, 24 Nov 2021 02:33:49 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 0E1EC400A6; 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Tue, 23 Nov 2021 18:33:39 -0800 (PST) X-Google-Smtp-Source: ABdhPJzJWRacun7W/BHsQL8YnMJOFffJa/FKnSoaoTDtgeSr1Mt6ke2qFcv4Usp7jKaQufiJXnZP+xRPr9o6CDcyZ8k= X-Received: by 2002:ac2:5310:: with SMTP id c16mr10809303lfh.580.1637721219040; Tue, 23 Nov 2021 18:33:39 -0800 (PST) MIME-Version: 1.0 References: <20211027022107.14357-1-jasowang@redhat.com> <20211027022107.14357-2-jasowang@redhat.com> <20211119160951.5f2294c8.pasic@linux.ibm.com> <20211122063518.37929c01.pasic@linux.ibm.com> <20211122064922.51b3678e.pasic@linux.ibm.com> <20211122212352.4a76232d.pasic@linux.ibm.com> <20211123055906-mutt-send-email-mst@kernel.org> <87zgpupcga.fsf@mpe.ellerman.id.au> In-Reply-To: From: Jason Wang Date: Wed, 24 Nov 2021 10:33:28 +0800 Message-ID: Subject: Re: [PATCH V5 1/4] virtio_ring: validate used buffer length To: Michael Ellerman Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jasowang@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Cc: "kaplan, david" , "Michael S. Tsirkin" , "Hetzelt, Felicitas" , linux-kernel , virtualization , Halil Pasic , mcgrof@kernel.org, Stefan Hajnoczi , Konrad Rzeszutek Wilk X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Wed, Nov 24, 2021 at 10:26 AM Jason Wang wrote: > > On Wed, Nov 24, 2021 at 9:30 AM Michael Ellerman wrote: > > > > "Michael S. Tsirkin" writes: > > > On Tue, Nov 23, 2021 at 10:25:20AM +0800, Jason Wang wrote: > > >> On Tue, Nov 23, 2021 at 4:24 AM Halil Pasic wrote: > > >> > > > >> > On Mon, 22 Nov 2021 14:25:26 +0800 > > >> > Jason Wang wrote: > > >> > > > >> > > I think the fixes are: > > >> > > > > >> > > 1) fixing the vhost vsock > > >> > > 2) use suppress_used_validation=true to let vsock driver to validate > > >> > > the in buffer length > > >> > > 3) probably a new feature so the driver can only enable the validation > > >> > > when the feature is enabled. > > >> > > > >> > I'm not sure, I would consider a F_DEV_Y_FIXED_BUG_X a perfectly good > > >> > feature. Frankly the set of such bugs is device implementation > > >> > specific and it makes little sense to specify a feature bit > > >> > that says the device implementation claims to adhere to some > > >> > aspect of the specification. Also what would be the semantic > > >> > of not negotiating F_DEV_Y_FIXED_BUG_X? > > >> > > >> Yes, I agree. Rethink of the feature bit, it seems unnecessary, > > >> especially considering the driver should not care about the used > > >> length for tx. > > >> > > >> > > > >> > On the other hand I see no other way to keep the validation > > >> > permanently enabled for fixed implementations, and get around the problem > > >> > with broken implementations. So we could have something like > > >> > VHOST_USED_LEN_STRICT. > > >> > > >> It's more about a choice of the driver's knowledge. For vsock TX it > > >> should be fine. If we introduce a parameter and disable it by default, > > >> it won't be very useful. > > >> > > >> > > > >> > Maybe, we can also think of 'warn and don't alter behavior' instead of > > >> > 'warn' and alter behavior. Or maybe even not having such checks on in > > >> > production, but only when testing. > > >> > > >> I think there's an agreement that virtio drivers need more hardening, > > >> that's why a lot of patches were merged. Especially considering the > > >> new requirements came from confidential computing, smart NIC and > > >> VDUSE. For virtio drivers, enabling the validation may help to > > >> > > >> 1) protect the driver from the buggy and malicious device > > >> 2) uncover the bugs of the devices (as vsock did, and probably rpmsg) > > >> 3) force the have a smart driver that can do the validation itself > > >> then we can finally remove the validation in the core > > >> > > >> So I'd like to keep it enabled. > > >> > > >> Thanks > > > > > > Let's see how far we can get. But yes, maybe we were too aggressive in > > > breaking things by default, a warning might be a better choice for a > > > couple of cycles. > > Ok, considering we saw the issues with balloons I think I can post a > patch to use warn instead. I wonder if we need to taint the kernel in > this case. Rethink this, consider we still have some time, I tend to convert the drivers to validate the length by themselves. Does this make sense? Thanks > > > > > This series appears to break the virtio_balloon driver as well. > > > > The symptom is soft lockup warnings, eg: > > > > INFO: task kworker/1:1:109 blocked for more than 614 seconds. > > Not tainted 5.16.0-rc2-gcc-10.3.0 #21 > > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > > task:kworker/1:1 state:D stack:12496 pid: 109 ppid: 2 flags:0x00000800 > > Workqueue: events_freezable update_balloon_size_func > > Call Trace: > > [c000000003cef7c0] [c000000003cef820] 0xc000000003cef820 (unreliable) > > [c000000003cef9b0] [c00000000001e238] __switch_to+0x1e8/0x2f0 > > [c000000003cefa10] [c000000000f0a00c] __schedule+0x2cc/0xb50 > > [c000000003cefae0] [c000000000f0a8fc] schedule+0x6c/0x140 > > [c000000003cefb10] [c00000000095b6c4] tell_host+0xe4/0x130 > > [c000000003cefba0] [c00000000095d234] update_balloon_size_func+0x394/0x3f0 > > [c000000003cefc70] [c000000000178064] process_one_work+0x2c4/0x5b0 > > [c000000003cefd10] [c0000000001783f8] worker_thread+0xa8/0x640 > > [c000000003cefda0] [c000000000185444] kthread+0x1b4/0x1c0 > > [c000000003cefe10] [c00000000000cee4] ret_from_kernel_thread+0x5c/0x64 > > > > Similar backtrace reported here by Luis: > > > > https://lore.kernel.org/lkml/YY2duTi0wAyAKUTJ@bombadil.infradead.org/ > > > > Bisect points to: > > > > # first bad commit: [939779f5152d161b34f612af29e7dc1ac4472fcf] virtio_ring: validate used buffer length > > > > Adding suppress used validation to the virtio balloon driver "fixes" it, eg. > > > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > > index c22ff0117b46..a14b82ceebb2 100644 > > --- a/drivers/virtio/virtio_balloon.c > > +++ b/drivers/virtio/virtio_balloon.c > > @@ -1150,6 +1150,7 @@ static unsigned int features[] = { > > }; > > > > static struct virtio_driver virtio_balloon_driver = { > > + .suppress_used_validation = true, > > .feature_table = features, > > .feature_table_size = ARRAY_SIZE(features), > > .driver.name = KBUILD_MODNAME, > > Looks good, we need a formal patch for this. > > And we need fix Qemu as well which advertise non zero used length for > inflate/deflate queue: > > static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq) > ... > virtqueue_push(vq, elem, offset); > > Thanks > > > > > > > cheers > > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization