drm: mxsfb: Fix NULL pointer dereference

[ Upstream commit 622c9a3a7868e1eeca39c55305ca3ebec4742b64 ]

mxsfb should not ever dereference the NULL pointer which
drm_atomic_get_new_bridge_state is allowed to return.
Assume a fixed format instead.

Fixes: b776b0f00f24 ("drm: mxsfb: Use bus_format from the nearest bridge if present")
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Marek Vasut <marex@denx.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220202081755.145716-3-alexander.stein@ew.tq-group.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
index b96ba34..988bc4f 100644 (file)
--- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
@@ -361,7 +361,11 @@ static void mxsfb_crtc_atomic_enable(struct drm_crtc *crtc,
                bridge_state =
                        drm_atomic_get_new_bridge_state(state,
                                                        mxsfb->bridge);
-               bus_format = bridge_state->input_bus_cfg.format;
+               if (!bridge_state)
+                       bus_format = MEDIA_BUS_FMT_FIXED;
+               else
+                       bus_format = bridge_state->input_bus_cfg.format;
+
                if (bus_format == MEDIA_BUS_FMT_FIXED) {
                        dev_warn_once(drm->dev,
                                      "Bridge does not provide bus format, assuming MEDIA_BUS_FMT_RGB888_1X24.\n"