Re: [PATCH] hw/pvrdma: Protect against buggy or malicious guest driver

[Marcel Apfelbaum]

Hi Yuval

On Mon, Mar 21, 2022 at 2:11 PM Yuval Shaia <yuval.shaia.ml@gmail.com> wrote:
>
> Guest driver might execute HW commands when shared buffers are not yet
> allocated.
> This might happen on purpose (malicious guest) or because some other
> guest/host address mapping.
> We need to protect againts such case.
>
> Reported-by: Mauro Matteo Cascella <mcascell@redhat.com>
> Signed-off-by: Yuval Shaia <yuval.shaia.ml@gmail.com>
> ---
>  hw/rdma/vmw/pvrdma_cmd.c  | 6 ++++++
>  hw/rdma/vmw/pvrdma_main.c | 9 +++++----
>  2 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/hw/rdma/vmw/pvrdma_cmd.c b/hw/rdma/vmw/pvrdma_cmd.c
> index da7ddfa548..89db963c46 100644
> --- a/hw/rdma/vmw/pvrdma_cmd.c
> +++ b/hw/rdma/vmw/pvrdma_cmd.c
> @@ -796,6 +796,12 @@ int pvrdma_exec_cmd(PVRDMADev *dev)
>
>      dsr_info = &dev->dsr_info;
>
> +    if (!dsr_info->dsr) {
> +            /* Buggy or malicious guest driver */
> +            rdma_error_report("Exec command without dsr, req or rsp 
> buffers");
> +            goto out;
> +    }
> +
>      if (dsr_info->req->hdr.cmd >= sizeof(cmd_handlers) /
>                        sizeof(struct cmd_handler)) {
>          rdma_error_report("Unsupported command");
> diff --git a/hw/rdma/vmw/pvrdma_main.c b/hw/rdma/vmw/pvrdma_main.c
> index 91206dbb8e..aae382af59 100644
> --- a/hw/rdma/vmw/pvrdma_main.c
> +++ b/hw/rdma/vmw/pvrdma_main.c
> @@ -159,13 +159,13 @@ static void free_dsr(PVRDMADev *dev)
>      free_dev_ring(pci_dev, &dev->dsr_info.cq, dev->dsr_info.cq_ring_state);
>
>      rdma_pci_dma_unmap(pci_dev, dev->dsr_info.req,
> -                         sizeof(union pvrdma_cmd_req));
> +                       sizeof(union pvrdma_cmd_req));
>
>      rdma_pci_dma_unmap(pci_dev, dev->dsr_info.rsp,
> -                         sizeof(union pvrdma_cmd_resp));
> +                       sizeof(union pvrdma_cmd_resp));
>
>      rdma_pci_dma_unmap(pci_dev, dev->dsr_info.dsr,
> -                         sizeof(struct pvrdma_device_shared_region));
> +                       sizeof(struct pvrdma_device_shared_region));
>

Nit: the above changes are not related to the patch, maybe drop them?

Reviewed-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>

Thanks,
Marcel

>      dev->dsr_info.dsr = NULL;
>  }
> @@ -249,7 +249,8 @@ static void init_dsr_dev_caps(PVRDMADev *dev)
>  {
>      struct pvrdma_device_shared_region *dsr;
>
> -    if (dev->dsr_info.dsr == NULL) {
> +    if (!dev->dsr_info.dsr) {
> +        /* Buggy or malicious guest driver */
>          rdma_error_report("Can't initialized DSR");
>          return;
>      }
> --
> 2.20.1
>