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@xxxxxxxxxxxxxxx; agraf@xxxxxxx; Yoder Stuart- > > B08248; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; bhelgaas@xxxxxxxxxx; linuxppc- > > dev@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > > 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@xxxxxxxxxxxxxxx; agraf@xxxxxxx; > > > > Yoder Stuart- B08248; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; > > > > bhelgaas@xxxxxxxxxx; linuxppc- dev@xxxxxxxxxxxxxxxx; > > > > linux-kernel@xxxxxxxxxxxxxxx > > > > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
