The mxsfb driver will crash if the mxsfb DT node has a subnode, but the content of the subnode is not of-graph binding with an endpoint linking to panel. The crash was triggered by providing old-style panel bindings to the mxsfb driver instead of the new of-graph ones.

The problem happens in mxsfb_create_output(), which is invoked from mxsfb_load(). The mxsfb_create_output() iterates over all mxsfb DT subnode endpoints and tries to bind a panel on each endpoint. If there is any problem binding the panel, that is, mxsfb->panel == NULL, this function will return an error code, otherwise success 0 is returned.

If the subnodes do not specify of-graph binding with an endpoint, the iteration over endpoints in mxsfb_create_output() will have zero cycles and the function will immediatelly return 0, but the mxsfb->panel will remain NULL. This is propagated back into the mxsfb_load(), which does not detect any problem and expects that the mxsfb->panel is valid, thus calls mxsfb_panel_attach(). But since mxsfb->panel == NULL, mxsfb_panel_attach() is called with first argument NULL and this crashes the kernel.

This patch fixes the problem by explicitly checking for valid mxsfb->panel at the end of the iteration in mxsfb_create_output().

Signed-off-by: Marek Vasut marex@denx.de Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Dave Airlie airlied@redhat.com Cc: Stefan Agner stefan@agner.ch Cc: Breno Matheus Lima brenomatheus@gmail.com --- drivers/gpu/drm/mxsfb/mxsfb_out.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/mxsfb/mxsfb_out.c b/drivers/gpu/drm/mxsfb/mxsfb_out.c index fa8d17399407..b8e81422d4e2 100644 --- a/drivers/gpu/drm/mxsfb/mxsfb_out.c +++ b/drivers/gpu/drm/mxsfb/mxsfb_out.c @@ -112,6 +112,7 @@ static int mxsfb_attach_endpoint(struct drm_device *drm,

int mxsfb_create_output(struct drm_device *drm) { + struct mxsfb_drm_private *mxsfb = drm->dev_private; struct device_node *ep_np = NULL; struct of_endpoint ep; int ret; @@ -127,5 +128,8 @@ int mxsfb_create_output(struct drm_device *drm) } }

+ if (!mxsfb->panel) + return -EPROBE_DEFER; + return 0; }