On Tue, Sep 08, 2020 at 08:29:04AM -0600, Alex Williamson wrote: > On Tue, 8 Sep 2020 01:47:08 +0530 > Ajay Kaher <[email protected]> wrote: > > > CVE-2020-12888 Kernel: vfio: access to disabled MMIO space of some > > devices may lead to DoS scenario > > > > The VFIO modules allow users (guest VMs) to enable or disable access to the > > devices' MMIO memory address spaces. If a user attempts to access > > (read/write) > > the devices' MMIO address space when it is disabled, some h/w devices issue > > an > > interrupt to the CPU to indicate a fatal error condition, crashing the > > system. > > This flaw allows a guest user or process to crash the host system resulting > > in > > a denial of service. > > > > Patch 1/ is to force the user fault if PFNMAP vma might be DMA mapped > > before user access. > > > > Patch 2/ setup a vm_ops handler to support dynamic faulting instead of > > calling > > remap_pfn_range(). Also provides a list of vmas actively mapping the area > > which > > can later use to invalidate those mappings. > > > > Patch 3/ block the user from accessing memory spaces which is disabled by > > using > > new vma list support to zap, or invalidate, those memory mappings in order > > to > > force them to be faulted back in on access. > > > > Upstreamed patches link: > > https://lore.kernel.org/kvm/[email protected] > > > > [PATCH v4.14.y 1/3]: > > Backporting of upsream commit 41311242221e: > > vfio/type1: Support faulting PFNMAP vmas > > > > [PATCH v4.14.y 2/3]: > > Backporting of upsream commit 11c4cd07ba11: > > vfio-pci: Fault mmaps to enable vma tracking > > > > [PATCH v4.14.y 3/3]: > > Backporting of upsream commit abafbc551fdd: > > vfio-pci: Invalidate mmaps and block MMIO access on disabled memory > > > > I'd recommend also including the following or else SR-IOV VFs will be > broken for DPDK: > > commit ebfa440ce38b7e2e04c3124aa89c8a9f4094cf21 > Author: Alex Williamson <[email protected]> > Date: Thu Jun 25 11:04:23 2020 -0600 > > vfio/pci: Fix SR-IOV VF handling with MMIO blocking > > SR-IOV VFs do not implement the memory enable bit of the command > register, therefore this bit is not set in config space after > pci_enable_device(). This leads to an unintended difference > between PF and VF in hand-off state to the user. We can correct > this by setting the initial value of the memory enable bit in our > virtualized config space. There's really no need however to > ever fault a user on a VF though as this would only indicate an > error in the user's management of the enable bit, versus a PF > where the same access could trigger hardware faults. > > Fixes: abafbc551fdd ("vfio-pci: Invalidate mmaps and block MMIO access on > disabled memory") > Signed-off-by: Alex Williamson <[email protected]>
Good catch, now queued up, thanks. greg k-h
