drm/vmwgfx: Fix up user_dmabuf refcounting
If user space calls unreference on a user_dmabuf it will typically
kill the struct ttm_base_object member which is responsible for the
user-space visibility. However the dmabuf part may still be alive and
refcounted. In some situations, like for shared guest-backed surface
referencing/opening, the driver may try to reference the
struct ttm_base_object member again, causing an immediate kernel warning
and a later kernel NULL pointer dereference.
Fix this by always maintaining a reference on the struct
ttm_base_object member, in situations where it might subsequently be
referenced.
Cc: <stable@vger.kernel.org>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
index b565654..5da5de0 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
@@ -1236,7 +1236,8 @@
struct vmw_relocation *reloc;
int ret;
- ret = vmw_user_dmabuf_lookup(sw_context->fp->tfile, handle, &vmw_bo);
+ ret = vmw_user_dmabuf_lookup(sw_context->fp->tfile, handle, &vmw_bo,
+ NULL);
if (unlikely(ret != 0)) {
DRM_ERROR("Could not find or use MOB buffer.\n");
ret = -EINVAL;
@@ -1296,7 +1297,8 @@
struct vmw_relocation *reloc;
int ret;
- ret = vmw_user_dmabuf_lookup(sw_context->fp->tfile, handle, &vmw_bo);
+ ret = vmw_user_dmabuf_lookup(sw_context->fp->tfile, handle, &vmw_bo,
+ NULL);
if (unlikely(ret != 0)) {
DRM_ERROR("Could not find or use GMR region.\n");
ret = -EINVAL;