From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Subject: Re: [PATCH] virtio_mem: prevent overflow with subblock size Date: Mon, 8 Jun 2020 09:34:51 +0200 Message-ID: <201e8ab5-ec50-af86-0ffc-d25befdba14e@redhat.com> References: <20200608061406.709211-1-mst@redhat.com> <0930c9d0-0708-c079-29bd-b80d4e3ce446@redhat.com> <2D9A07BA-6FDC-48FF-9A1F-62272695B3EF@linux.alibaba.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <2D9A07BA-6FDC-48FF-9A1F-62272695B3EF@linux.alibaba.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: teawater Cc: "Michael S. Tsirkin" , LKML , Jason Wang , Pankaj Gupta , virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org On 08.06.20 09:12, teawater wrote: > > >> 2020年6月8日 14:58，David Hildenbrand 写道： >> >> On 08.06.20 08:14, Michael S. Tsirkin wrote: >>> If subblock size is large (e.g. 1G) 32 bit math involving it >>> can overflow. Rather than try to catch all instances of that, >>> let's tweak block size to 64 bit. >> >> I fail to see where we could actually trigger an overflow. The reported >> warning looked like a false positive to me. >> >>> >>> It ripples through UAPI which is an ABI change, but it's not too late to >>> make it, and it will allow supporting >4Gbyte blocks while might >>> become necessary down the road. >>> >> >> This might break cloud-hypervisor, who's already implementing this >> protocol upstream (ccing Hui). >> https://github.com/cloud-hypervisor/cloud-hypervisor/blob/master/vm-virtio/src/mem.rs >> >> (blocks in the gigabyte range were never the original intention of >> virtio-mem, but I am not completely opposed to that) > > If you think virtio_mem need this patch, I think cloud-hypervisor should follow this update (I will post PR for it). Thanks Hui. So we can still do last-minute changes if we all agree it makes sense. @MST can you rephrase the patch description to highlight that this is a preparation for the future only and not actually currently broken? "virtio-mem: convert device block size into 64bit" ... With that Acked-by: David Hildenbrand -- Thanks, David / dhildenb