Re: [PATCH v6 01/15] hw/nvme: Use pcie_sriov_num_vfs()

[Klaus Jensen <its@irrelevant.dk>]

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On Feb 20 15:29, Kevin Wolf wrote:
> Am 20.02.2024 um 13:24 hat Akihiko Odaki geschrieben:
> > nvme_sriov_pre_write_ctrl() used to directly inspect SR-IOV
> > configurations to know the number of VFs being disabled due to SR-IOV
> > configuration writes, but the logic was flawed and resulted in
> > out-of-bound memory access.
> > 
> > It assumed PCI_SRIOV_NUM_VF always has the number of currently enabled
> > VFs, but it actually doesn't in the following cases:
> > - PCI_SRIOV_NUM_VF has been set but PCI_SRIOV_CTRL_VFE has never been.
> > - PCI_SRIOV_NUM_VF was written after PCI_SRIOV_CTRL_VFE was set.
> > - VFs were only partially enabled because of realization failure.
> > 
> > It is a responsibility of pcie_sriov to interpret SR-IOV configurations
> > and pcie_sriov does it correctly, so use pcie_sriov_num_vfs(), which it
> > provides, to get the number of enabled VFs before and after SR-IOV
> > configuration writes.
> > 
> > Cc: qemu-stable@nongnu.org
> > Fixes: CVE-2024-26328
> > Fixes: 11871f53ef8e ("hw/nvme: Add support for the Virtualization Management command")
> > Suggested-by: Michael S. Tsirkin <mst@redhat.com>
> > Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> > ---
> >  hw/nvme/ctrl.c | 26 ++++++++------------------
> >  1 file changed, 8 insertions(+), 18 deletions(-)
> > 
> > diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
> > index f026245d1e9e..7a56e7b79b4d 100644
> > --- a/hw/nvme/ctrl.c
> > +++ b/hw/nvme/ctrl.c
> > @@ -8466,36 +8466,26 @@ static void nvme_pci_reset(DeviceState *qdev)
> >      nvme_ctrl_reset(n, NVME_RESET_FUNCTION);
> >  }
> >  
> > -static void nvme_sriov_pre_write_ctrl(PCIDevice *dev, uint32_t address,
> > -                                      uint32_t val, int len)
> > +static void nvme_sriov_post_write_config(PCIDevice *dev, uint16_t old_num_vfs)
> >  {
> >      NvmeCtrl *n = NVME(dev);
> >      NvmeSecCtrlEntry *sctrl;
> > -    uint16_t sriov_cap = dev->exp.sriov_cap;
> > -    uint32_t off = address - sriov_cap;
> > -    int i, num_vfs;
> > +    int i;
> >  
> > -    if (!sriov_cap) {
> > -        return;
> > -    }
> > -
> > -    if (range_covers_byte(off, len, PCI_SRIOV_CTRL)) {
> > -        if (!(val & PCI_SRIOV_CTRL_VFE)) {
> > -            num_vfs = pci_get_word(dev->config + sriov_cap + PCI_SRIOV_NUM_VF);
> > -            for (i = 0; i < num_vfs; i++) {
> > -                sctrl = &n->sec_ctrl_list.sec[i];
> > -                nvme_virt_set_state(n, le16_to_cpu(sctrl->scid), false);
> > -            }
> > -        }
> > +    for (i = pcie_sriov_num_vfs(dev); i < old_num_vfs; i++) {
> > +        sctrl = &n->sec_ctrl_list.sec[i];
> > +        nvme_virt_set_state(n, le16_to_cpu(sctrl->scid), false);
> >      }
> >  }
> 
> Maybe I'm missing something, but if the concern is that 'i' could run
> beyond the end of the array, I don't see anything that limits
> pcie_sriov_num_vfs() to the static size of 127 that n->sec_ctrl_list.sec
> has. register_vfs() seems to just take whatever 16 bit value the guest
> wrote without imposing additional restrictions.
> 

Hi Kevin,

Thanks for reviewing, I believe patch 2 in this series fixes that
missing validation of NumVFs.

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