ACK: [PATCH Y/Z] drm/vmwgfx: Make sure backup_handle is always valid

[Po-Hsu Lin]

On Thu, Jun 22, 2017 at 11:28 PM, Stefan Bader <stefan.bader at canonical.com> wrote:
> From: Sinclair Yeh <syeh at vmware.com>
>
> When vmw_gb_surface_define_ioctl() is called with an existing buffer,
> we end up returning an uninitialized variable in the backup_handle.
>
> The fix is to first initialize backup_handle to 0 just to be sure, and
> second, when a user-provided buffer is found, we will use the
> req->buffer_handle as the backup_handle.
>
> Cc: <stable at vger.kernel.org>
> Reported-by: Murray McAllister <murray.mcallister at insomniasec.com>
> Signed-off-by: Sinclair Yeh <syeh at vmware.com>
> Reviewed-by: Deepak Rawat <drawat at vmware.com>
>
> CVE-2017-9605
>
> (cherry picked from commit 07678eca2cf9c9a18584e546c2b2a0d0c9a3150c)
> Signed-off-by: Stefan Bader <stefan.bader at canonical.com>
+1
Acked-by: Po-Hsu Lin <po-hsu.lin at canonical.com>

> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
> index baf03d4..834bb10 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
> @@ -1274,7 +1274,7 @@ int vmw_gb_surface_define_ioctl(struct drm_device *dev, void *data,
>         struct ttm_object_file *tfile = vmw_fpriv(file_priv)->tfile;
>         int ret;
>         uint32_t size;
> -       uint32_t backup_handle;
> +       uint32_t backup_handle = 0;
>
>         if (req->multisample_count != 0)
>                 return -EINVAL;
> @@ -1317,12 +1317,16 @@ int vmw_gb_surface_define_ioctl(struct drm_device *dev, void *data,
>                 ret = vmw_user_dmabuf_lookup(tfile, req->buffer_handle,
>                                              &res->backup,
>                                              &user_srf->backup_base);
> -               if (ret == 0 && res->backup->base.num_pages * PAGE_SIZE <
> -                   res->backup_size) {
> -                       DRM_ERROR("Surface backup buffer is too small.\n");
> -                       vmw_dmabuf_unreference(&res->backup);
> -                       ret = -EINVAL;
> -                       goto out_unlock;
> +               if (ret == 0) {
> +                       if (res->backup->base.num_pages * PAGE_SIZE <
> +                           res->backup_size) {
> +                               DRM_ERROR("Surface backup buffer is too small.\n");
> +                               vmw_dmabuf_unreference(&res->backup);
> +                               ret = -EINVAL;
> +                               goto out_unlock;
> +                       } else {
> +                               backup_handle = req->buffer_handle;
> +                       }
>                 }
>         } else if (req->drm_surface_flags & drm_vmw_surface_flag_create_buffer)
>                 ret = vmw_user_dmabuf_alloc(dev_priv, tfile,
> --
> 2.7.4
>
>
> --
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