On 25/06/2020 19:33, Wang, Haiyue wrote: >> -----Original Message----- >> From: Kevin Traynor <ktray...@redhat.com> >> Sent: Friday, June 26, 2020 00:46 >> To: David Marchand <david.march...@redhat.com>; Wang, Haiyue >> <haiyue.w...@intel.com>; Luca Boccassi >> <bl...@debian.org> >> Cc: dev <dev@dpdk.org>; Burakov, Anatoly <anatoly.bura...@intel.com>; dpdk >> stable <sta...@dpdk.org>; >> Harman Kalra <hka...@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.w...@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: sta...@dpdk.org >>>> >>>> Signed-off-by: Haiyue Wang <haiyue.w...@intel.com> >>>> Acked-by: Anatoly Burakov <anatoly.bura...@intel.com> >>>> Tested-by: Harman Kalra <hka...@marvell.com> >>>> Tested-by: David Marchand <david.march...@redhat.com> >>> Tested-by: Thierry Martin <thierry.martin.pub...@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. ;-) >
Thanks for the update Haiyue. That may be true in the future, but not at the moment. The patch is just submitted yesterday, so I don't know how long it will take to filter through to all the distro kernels (and users to update). I think it's still worth to take this patch now in 18.11. I will wait until this afternoon in case anyone has reasons not to. thanks, Kevin. > https://lore.kernel.org/kvm/159310421505.27590.16617666489295503039.st...@gimli.home/T/#u >
