From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 39D063F9F5B; Fri, 17 Jul 2026 11:01:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784286071; cv=none; b=Bcld4V6hEdJd8n4yBcgLvYV78EVSPiBLvHKrUj0+q2tlyqzitkX8L2YIsTTpVHLm8u5z06kXjsMyh+x2860rciYT8iJR8yJd6ot+gDQpJ0ZBsLSbYpjzvNx78/0RNISkroSwWHn1xbnv7WqfvF5p1Njlhl0MINsmjaMjhEuFl90= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784286071; c=relaxed/simple; bh=PhH4mV1/strXjwckUIs9u5WM43ype4MZV/chQOTZ/xk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=flZ+06i1lPt3uSQlehzwLKplSsiCGdThZQDwGTIyH9NQGMYOnii8FE0RSHHXSpmErrMcC1S1IVODQhsMgz0+dznuuVXCnAokeoO0Q+qyUhmscWgjQ6IZZmeQQRjoMSXPydr+bsWAbkWbkSVS6n7mud/67sPpcH42Q0f/2dWejSE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gyW+vVuB; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="gyW+vVuB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9289D1F000E9; Fri, 17 Jul 2026 11:01:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784286062; bh=TODRWsZXUbm+1HGqxa8f3PD0N5/amuglrNxCUjdbOXg=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=gyW+vVuBz3RRP4nVJCbEhVx1YzIYSCsleduMEsXYR+XWR9A+FDJ6tAfFbqwHC8V3m ZUwzc6f3bFD4yR3xBKJPGv3Y4LKfPfsxLjzARyNc5BDF0HVejWCPR71Eh9F0Jd/jhF 5nl/CXoUACeREQxFQVdirIflBoPjLLS5/Y6Vg9XQ5oGm+b3Ikd6GqqZPZxdpxjnCdg M+8Zmufgyk/ivCd8MMry1Wqv3o/q3nXl6EDvg6zyTmxlm611r6f86c8GfQFM7qeGet PEeFfNOSByqTPa2shMoUZ426DKOkK8xFzEZkmqp65Cu2wESLB8bQOavPYNDk74uDKX pA5Tvcpi5iMdQ== Message-ID: <0b1d22bb-f929-45ca-bfd9-a1598791cff3@kernel.org> Date: Fri, 17 Jul 2026 12:00:58 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/4] virtio-mem: validate device-reported block size To: Greg Kroah-Hartman Cc: "Michael S. Tsirkin" , Hari Mishal , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, elena.reshetova@intel.com, carlos.bilbao.osdev@gmail.com References: <2026071635-relive-flogging-2a81@gregkh> <4dda47ba-534a-4297-a25e-0d63d9167033@kernel.org> <20260717014134-mutt-send-email-mst@kernel.org> <3b32a38f-0964-45b9-9529-933abedbf69b@kernel.org> <20260717044019-mutt-send-email-mst@kernel.org> <2026071746-deviation-clad-1712@gregkh> <20260717060822-mutt-send-email-mst@kernel.org> <2026071757-grout-composer-165d@gregkh> <5877a6ae-5a9c-4376-8297-f17695964db0@kernel.org> <2026071717-unfiled-manned-3305@gregkh> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <2026071717-unfiled-manned-3305@gregkh> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/17/26 12:44, Greg Kroah-Hartman wrote: > On Fri, Jul 17, 2026 at 11:21:34AM +0100, David Hildenbrand (Arm) wrote: >> On 7/17/26 12:15, Greg Kroah-Hartman wrote: >>> >>> Ok, so you want this patch :) >> >> I fail to see the value of this patch given that there are plenty of other cases >> the device can mess with us. > > How can the device mess with us? I raised some examples already, like lying about which memory chunks it makes available. I guess it could also throw a random "requested_size" at us. It could make up a wrong physical address region. I assume there is plenty more we'd have to check. Again, I'm not saying that this couldn't/shouldn't be done, but it requires some *real thought* about all possible things a device could do. > >> But sure, let's check for some conditions if it makes us feel warm and fluffy as >> we audited a driver and it's now super safe, fine with me. > > I'm all for the folly of "it's an audited driver!" claims, but you all > need to decide either you do or you do not trust the device. Either way > is fine with me. Well, exactly, that is what I am saying. I don't know what we care about. This patch here feels incomplete and that's what grinds my gears. It doesn't magically make us deal with malicious devices. And I don't buy the story about "buggy virtio-mem devices that set block_size==0", which doesn't make any sense in any possible reality. > > If you don't trust it, great, take patches that fix that. If you do > trust it, great, reject those types of patches. > > But pick one please. Yes, I'd expect that we have general virtio guifance. I only co-maintain some virtio bits and have no idea about the expected trust model and when we would consider a devices trusted. And what it would take to get there. -- Cheers, David