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[80.230.24.117]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4954a2e850dsm40816685e9.9.2026.07.17.03.28.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Jul 2026 03:28:43 -0700 (PDT) Date: Fri, 17 Jul 2026 06:28:40 -0400 From: "Michael S. Tsirkin" To: "David Hildenbrand (Arm)" Cc: Greg Kroah-Hartman , Hari Mishal , Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, elena.reshetova@intel.com, carlos.bilbao.osdev@gmail.com Subject: Re: [PATCH v2 1/4] virtio-mem: validate device-reported block size Message-ID: <20260717062436-mutt-send-email-mst@kernel.org> 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5877a6ae-5a9c-4376-8297-f17695964db0@kernel.org> On Fri, Jul 17, 2026 at 11:21:34AM +0100, David Hildenbrand (Arm) wrote: > On 7/17/26 12:15, Greg Kroah-Hartman wrote: > > On Fri, Jul 17, 2026 at 06:10:41AM -0400, Michael S. Tsirkin wrote: > >> On Fri, Jul 17, 2026 at 11:14:23AM +0200, Greg Kroah-Hartman wrote: > >>> > >>> Why not do what USB does? Don't trust the device until AFTER probe() > >>> succeeds? All of the needed checking should happen before then, as that > >>> is a "slow path" so lots of validation and the like can happen at that > >>> point. > >>> > >>> After that, during the normal data paths, after the driver is bound, > >>> trust it all you want as attempting to validate every single packet is > >>> just going to be impossible. > >>> > >>> thanks, > >>> > >>> greg k-h > >> > >> People do expect that data path validation at this point. > > > > 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. > > 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. > > -- > Cheers, > > David I merely made some generic comments since I was asked to clarify how virtio interacts with coco. As for the specific patch, it does not make me feel fluffy. It lacks motivation. A broken device confuses the kernel with no way to exploit that. Shrug. So? Nothing to do with coco, apparently. It's maybe reasonable as a debugging aid but if this is intended as such let's make it clear in the commit log. -- MST