Re: [dpdk-dev] [PATCH v4] bus/pci: fix VF bus error for memory access

["Wang, Haiyue" <haiyue.wang@intel.com>]

> -----Original Message-----
> From: Kevin Traynor <ktraynor@redhat.com>
> Sent: Friday, June 26, 2020 00:46
> To: David Marchand <david.marchand@redhat.com>; Wang, Haiyue <haiyue.wang@intel.com>; Luca Boccassi
> <bluca@debian.org>
> Cc: dev <dev@dpdk.org>; Burakov, Anatoly <anatoly.burakov@intel.com>; dpdk stable <stable@dpdk.org>;
> Harman Kalra <hkalra@marvell.com>
> Subject: Re: [PATCH v4] bus/pci: fix VF bus error for memory access
> 
> On 25/06/2020 15:09, David Marchand wrote:
> > On Thu, Jun 25, 2020 at 6:00 AM Haiyue Wang <haiyue.wang@intel.com> wrote:
> >>
> >> To fix CVE-2020-12888, the linux vfio-pci module will invalidate mmaps
> >> and block MMIO access on disabled memory, it will send a SIGBUS to the
> >> application:
> >>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=abafbc551fddede3e0a08dee
> 1dcde08fc0eb8476
> >>
> >> When the application opens the vfio PCI device, the vfio-pci module will
> >> enable the bus memory space through PCI read/write access. According to
> >> the PCIe specification, the 'Memory Space Enable' is always zero for VF:
> >>
> >>              Table 9-13 Command Register Changes
> >>
> >> Bit Location | PF and VF Register Differences | PF         | VF
> >>              | From Base                      | Attributes | Attributes
> >> -------------+--------------------------------+------------+-----------
> >>              | Memory Space Enable - Does not |            |
> >>              | apply to VFs. Must be hardwired|  Base      |  0b
> >>      1       | to 0b for VFs. VF Memory Space |            |
> >>              | is controlled by the VF MSE bit|            |
> >>              | in the VF Control register.    |            |
> >> -------------+--------------------------------+------------+-----------
> >>
> >> Afterwards the vfio-pci will initialize its own virtual PCI config space
> >> data ('vconfig') by reading the VF's physical PCI config space, then the
> >> 'Memory Space Enable' bit in vconfig will always be 0b value. This will
> >> make the vfio-pci treat the BAR memory space as disabled, and the SIGBUS
> >> will be triggered if access these BARs.
> >>
> >> By investigation, the VF PCI device *passthrough* into the Guest OS by
> >> QEMU has the 'Memory Space Enable' with 1b value. That's because every
> >> PCI driver will start to enable the memory space, and this action will
> >> be hooked by vfio-pci virtual PCI read/write to set the 'Memory Space
> >> Enable' in vconfig space to 1b. So VF runs in guest OS has 'Mem+', but
> >> VF runs in host OS has 'Mem-'.
> >>
> >> Align with PCI working mode in Guest/QEMU/Host, in DPDK, enable the PCI
> >> bus memory space explicitly to avoid access on disabled memory.
> >>
> >> Fixes: 33604c31354a ("vfio: refactor PCI BAR mapping")
> >> Cc: stable@dpdk.org
> >>
> >> Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
> >> Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
> >> Tested-by: Harman Kalra <hkalra@marvell.com>
> >> Tested-by: David Marchand <david.marchand@redhat.com>
> > Tested-by: Thierry Martin <thierry.martin.public@gmail.com>
> >
> > Applied, thanks again Haiyue.
> >
> >
> > Kevin, Luca,
> >
> > I can see that some distros have already started backporting the fix
> > in kernel (fc31, fc32 and rhel7 at least for what I saw).
> > 18.11 and 19.11 will need this fix at some point.
> > I'll let you decide on the proper timing.
> >
> >
> 
> It looks an important fix. I think it's worth having in 18.11.9. I will
> apply and create an 18.11.9-rc2 tomorrow, so if anyone hasn't started
> validation already, they can validate with it in.

Alex post a fix in kernel just now. So looks like the DPDK patch is nice
to have, not a MUST. ;-)

https://lore.kernel.org/kvm/159310421505.27590.16617666489295503039.stgit@gimli.home/T/#u