[PATCH] drm: mxsfb: Fix crash when provided invalid DT bindings

[Breno Matheus Lima]

2017-01-28 15:01 GMT-02:00 Marek Vasut <marex at denx.de>:
>
> 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 at denx.de>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Dave Airlie <airlied at redhat.com>
> Cc: Stefan Agner <stefan at agner.ch>
> Cc: Breno Matheus Lima <brenomatheus at gmail.com>

Tested-by: Breno Lima <breno.lima at nxp.com>
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