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 30B533502A3; Mon, 20 Jul 2026 07:57:18 +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=1784534240; cv=none; b=CpgCJoj25yJdm2DmXOUso3ev56CWE1iFMBo/Kf6c51YOLDbWC6w9piQ6BBlZUyfXnvhPp54evYbh8XynxRLfDwesm1lb1HP7WDb26VAcvmQBaf7LwYYK6pd4ByEFASYb+ItO9MRNjcZC5BCnMNF7eY7OTGATS+CtfKje7fVW+lw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784534240; c=relaxed/simple; bh=f+dSLCKr1c4O6kogYfegUckh3s10EtfuZYBQSeHXMlw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=kKbfTPevPn+D7Q3oxUL6AdTI91JUulsp75Ah6i7Q8Sc+QGpx/9OUoebF2we4x6iYS+4BV4QB1RxMzWStYlbYfsNthqgoeZ9etiaGYM3r0SzeBqremXhQXsvmndCAp5UVZ0K4dowT6fZSdISXm/Q9mMdfJ00hXewyeqN8WWnflpU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kc2fksw2; 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="kc2fksw2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B33801F000E9; Mon, 20 Jul 2026 07:57:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784534238; bh=HTc1DdLuxgcB4tAC6qIpYWdsraepckByndfkQacfo3E=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=kc2fksw2n0fS7T8FbzwsS+4nd1wgFpXutcmujZ6YV9Hq7MwHv+/ERaexD+5JiBZGF C9G2Gdumn2RdSLx0PIGQCfDH6y7PBjNodKdeo9wHNdLtYS5v6IOfYBJB1ughfHLW0s eVKdrQyDbzCXdp1SQJpJ5/LUtObIoPGxLXklB9LW4iy/kw7rhCnEO7GWTuVL0PeJvq rryWuT+yF4tc8j5c2de+u7H+slxY30jtuP4KrkTZW2xjEOq9mR17g2h2tx2Z49JWkc GlX5ZQel089zVaTTK66jzn/AULNloKjDZ8eikNw1eQSQw1mk6/GxSWlfAGgP/X1j4s quRrXdWMq4Z+g== Message-ID: <9569e577-aa82-4642-b9d9-fd496fc12849@kernel.org> Date: Mon, 20 Jul 2026 08:57:13 +0100 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev 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: Carlos Bilbao , 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, huster@cs.uni-goettingen.de, mhollick@seemoo.de, jiska.classen@hpi.de References: <20260717044019-mutt-send-email-mst@kernel.org> <2026071746-deviation-clad-1712@gregkh> <20260717060822-mutt-send-email-mst@kernel.org> <2026071757-grout-composer-165d@gregkh> <20260717061901-mutt-send-email-mst@kernel.org> <2026071724-asleep-pedigree-ea54@gregkh> <20260717065219-mutt-send-email-mst@kernel.org> <2026071759-thermal-synopsis-7568@gregkh> <20260717085838-mutt-send-email-mst@kernel.org> <1fe328d1-edf9-4e72-a145-be74ede20e60@gmail.com> <2026071803-passage-dares-8240@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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 7/18/26 18:07, Carlos Bilbao wrote: > On 7/17/26 22:29, Greg Kroah-Hartman wrote: > >> On Fri, Jul 17, 2026 at 08:31:09PM -0700, Carlos Bilbao wrote: >>> Historically, one of the biggest criticisms of coco, especially around >>> device hardening, was that there were too many values that a >>> malicious/buggy device could misreport, making it a losing battle. That is >>> no longer the case with LLMs, and we have the advantage (and challenge) of >>> open-source dev, which allows us to receive many of these fixes "for free". >>> If others want to burn their tokens, let them :) >> I have lots of tokens to burn :) >> >> So along those lines, any suggestions on how best to fuzz these code >> paths?  Any workloads you all use for testing that I can take advantage >> of? > > > We've the virtio-mem config struct layout and the kernel source, so for > obvious fixes like a NULL check, static analysis is better than fuzzing. > Claude took a few mins to find me two examples: > > Patch 1: virtio-mem: reject non-power-of-two device_block_size > This one is for virtio_mem_init() to check if > !is_power_of_2(vm->device_block_size) > > Patch 2: virto-mem: validate region_size and usable_region_size > THis one checks region_size != 0 and vm->usable_reion_size > > vm->region_size. > > An endless factory of "silly" checks like these are low hanging fruit. > > Now, for harder bugs, looking around for fuzz options, VirtFuzz [1] looks > like a great candidate for those interested in pursuing this direction. > > > Their PoC fuzzes wireless/Bluetooth stack, but nothing our AI overlords > can't quickly adapt for virtio-mem and other virtio drivers; the JSON > definition to describe device behavior is easily extensible. Their threat > model [2] describes an external attacker, but in the context of coco, the > virtio device itself is the attacker. Here's a vibe coded PR of what I mean: > > https://github.com/seemoo-lab/VirtFuzz/pull/7 > > CCed the creators/authors, thanks for open sourcing this! > > Thanks, > Carlos > > [1] https://github.com/seemoo-lab/VirtFuzz > > On 7/17/26 22:29, Greg Kroah-Hartman wrote: > >> On Fri, Jul 17, 2026 at 08:31:09PM -0700, Carlos Bilbao wrote: >>> Historically, one of the biggest criticisms of coco, especially around >>> device hardening, was that there were too many values that a >>> malicious/buggy device could misreport, making it a losing battle. That is >>> no longer the case with LLMs, and we have the advantage (and challenge) of >>> open-source dev, which allows us to receive many of these fixes "for free". >>> If others want to burn their tokens, let them :) >> I have lots of tokens to burn :) >> >> So along those lines, any suggestions on how best to fuzz these code >> paths?  Any workloads you all use for testing that I can take advantage >> of? > > > We've the virto-mem config struct layout and the kernel source, so for > obvious fixes like a NULL check, static analysis is better than fuzzing. > Claude took a few mins to find me two examples: > > Patch 1: virtio-mem: reject non-power-of-two device_block_size > This one is for virtio_mem_init() to check if > !is_power_of_2(vm->device_block_size) > > Patch 2: virto-mem: validate region_size and usable_region_size > THis one checks region_size != 0 and vm->usable_reion_size > > vm->region_size. > > An endless factory of "silly" checks like these are low hanging fruit. "silly" is the right word. -- Cheers, David