drm/vmwgfx: Make sure backup_handle is always valid

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@vger.kernel.org>
Reported-by: Murray McAllister <murray.mcallister@insomniasec.com>
Signed-off-by: Sinclair Yeh <syeh@vmware.com>
Reviewed-by: Deepak Rawat <drawat@vmware.com>

1 files changed, 11 insertions, 7 deletions

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
index baf03d4d86d2..834bb10973a2 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,