From mboxrd@z Thu Jan 1 00:00:00 1970 From: Scott Wood Subject: Re: [PATCH 0/9 v2] vfio-pci: add support for Freescale IOMMU (PAMU) Date: Fri, 6 Dec 2013 12:59:53 -0600 Message-ID: <1386356393.7375.118.camel@snotra.buserror.net> References: <1384838233-24847-1-git-send-email-Bharat.Bhushan@freescale.com> <1384973243.2879.361.camel@ul30vt.home> <6A3DF150A5B70D4F9B66A25E3F7C888D0721D9AC@039-SN2MPN1-012.039d.mgd.msft.net> <1385066603.2879.414.camel@ul30vt.home> <1385066835.1403.489.camel@snotra.buserror.net> <1385067648.2879.421.camel@ul30vt.home> <6A3DF150A5B70D4F9B66A25E3F7C888D0722C180@039-SN2MPN1-012.039d.mgd.msft.net> <1385397493.2879.557.camel@ul30vt.home> <6A3DF150A5B70D4F9B66A25E3F7C888D0723624C@039-SN2MPN1-012.039d.mgd.msft.net> <1386289316.7375.107.camel@snotra.buserror.net> <6A3DF150A5B70D4F9B66A25E3F7C888D07251EE4@039-SN2MPN1-012.039d.mgd.msft.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <6A3DF150A5B70D4F9B66A25E3F7C888D07251EE4-RL0Hj/+nBVDAtPZc1oz0FK4g8xLGJsHaLnY5E4hWTkheoWH0uzbU5w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Bharat Bhushan Cc: "linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "agraf-l3A5Bk7waGM@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , Yoder Stuart-B08248 , "bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org" , "linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: iommu@lists.linux-foundation.org On Thu, 2013-12-05 at 22:11 -0600, Bharat Bhushan wrote: > > > -----Original Message----- > > From: Wood Scott-B07421 > > Sent: Friday, December 06, 2013 5:52 AM > > To: Bhushan Bharat-R65777 > > Cc: Alex Williamson; linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; agraf-l3A5Bk7waGM@public.gmane.org; Yoder Stuart- > > B08248; iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org; bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org; linuxppc- > > dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org; linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > > Subject: Re: [PATCH 0/9 v2] vfio-pci: add support for Freescale IOMMU (PAMU) > > > > On Thu, 2013-11-28 at 03:19 -0600, Bharat Bhushan wrote: > > > > > > > -----Original Message----- > > > > From: Bhushan Bharat-R65777 > > > > Sent: Wednesday, November 27, 2013 9:39 PM > > > > To: 'Alex Williamson' > > > > Cc: Wood Scott-B07421; linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; agraf-l3A5Bk7waGM@public.gmane.org; > > > > Yoder Stuart- B08248; iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org; > > > > bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org; linuxppc- dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org; > > > > linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > > > > Subject: RE: [PATCH 0/9 v2] vfio-pci: add support for Freescale > > > > IOMMU (PAMU) > > > > > > > > If we just provide the size of MSI bank to userspace then userspace > > > > cannot do anything wrong. > > > > > > So userspace does not know address, so it cannot mmap and cause any > > interference by directly reading/writing. > > > > That's security through obscurity... Couldn't the malicious user find out the > > address via other means, such as experimentation on another system over which > > they have full control? What would happen if the user reads from their device's > > PCI config space? Or gets the information via some back door in the PCI device > > they own? Or pokes throughout the address space looking for something that > > generates an interrupt to its own device? > > So how to solve this problem, Any suggestion ? > > We have to map one window in PAMU for MSIs and a malicious user can ask > its device to do DMA to MSI window region with any pair of address and > data, which can lead to unexpected MSIs in system? I don't think there are any solutions other than to limit each bank to one user, unless the admin turns some knob that says they're OK with the partial loss of isolation. -Scott