drm/vmwgfx: Fix kernel NULL pointer dereference on older hardware
The commit "drm/vmwgfx: Fix up user_dmabuf refcounting", while fixing a
kernel crash introduced a NULL pointer dereference on older hardware.
Fix this.
Cc: <stable@vger.kernel.org>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
index 64b5040..03f63c7 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
@@ -657,7 +657,8 @@
struct vmw_resource *res = &user_srf->srf.res;
*p_base = NULL;
- ttm_base_object_unref(&user_srf->backup_base);
+ if (user_srf->backup_base)
+ ttm_base_object_unref(&user_srf->backup_base);
vmw_resource_unreference(&res);
}