[PATCH 5.16 078/126] drm: mxsfb: Fix NULL pointer dereference

Greg Kroah-Hartman
2022-02-07T12:00:02Z

From: Alexander Stein <alexander.stein@ew.tq-group.com>

commit 622c9a3a7868e1eeca39c55305ca3ebec4742b64 upstream.

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpu/drm/mxsfb/mxsfb_kms.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- 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(str
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"